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Topical›Chemistry 9701›Electrochemistry›Redox processes: electron transfer and changes in oxidation number (oxidation state)›Paper 1

Redox processes: electron transfer and changes in oxidation number (oxidation state) — Paper 1 · A Level Chemistry 9701

6.1· 349 questions · 349 marks · 419 min · 2005–2025· Multiple choice

Every Cambridge A Level Chemistry Paper 1 question on redox processes: electron transfer and changes in oxidation number (oxidation state), laid out as 78 A4 pages with the mark scheme below. Nothing is left out. Free to read, no account.

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Question 1: Chlorine dioxide is produced on a large scale as it is used for bleaching paper pulp. It is made by the following reaction. 2Cl O (aq) + SO…Question 2: Chlorine reacts with hot concentrated aqueous sodium hydroxide according to the equation below. 3Cl2(g) + 6NaOH(aq) → NaCl O3(aq) + 5NaCl (…Question 3: The nickel-cadmium rechargeable battery is based upon the following overall reaction. Cd + 2NiOOH + 4H2O → Cd(OH)2 + 2Ni(OH)2.H2O What is t…Question 4: What happens when chlorine is bubbled through aqueous potassium iodide? A Chlorine is oxidised to chloride ions. B Hydrochloric acid is for…1 / 78
Question 5: Aldehydes and ketones are carbonyl compounds. Which of them react both with NaBH4 and with Tollens’ reagent? A both aldehydes and ketones B…Question 6: Ammonia and chlorine react in the gas phase. 8NH3 + 3Cl2 → N2 + 6NH4Cl Which statements are correct? 1 Ammonia behaves as a reducing agent.…Question 7: In some early paintings, lead(II) carbonate was used as a white pigment. In the 19th century hydrogen sulphide from burning coal reacted wi…Question 8: What happens when chlorine is bubbled through aqueous sodium hydroxide solution? 1 In cold solution, ClO–(aq) ions are formed. 2 In hot sol…Question 9: The first stage in the manufacture of nitric acid is the oxidation of ammonia by oxygen. wNH3(g) + xO2(g) → yNO(g) + zH2O(g) Which values f…2 / 78
Question 10: In an experiment, 50.0 cm3 of a 0.10 mol dm–3 solution of a metallic salt reacted exactly with 25.0 cm3 of 0.10 mol dm–3 aqueous sodium sul…Question 11: Carbon monoxide burns readily in oxygen to form carbon dioxide. What can be deduced from this information? 1 The +4 oxidation state of carb…Question 12: When the yellow liquid NCl3 is stirred into aqueous sodium hydroxide, the reaction that occurs can be represented by the following equation…Question 13: In some fireworks there is a reaction between powdered aluminium and powdered barium nitrate in which heat is evolved and an unreactive gas…Question 14: Which conversion involves a reduction of chromium? A CrO 2 − → CrO3 4 B CrO 2 − → Cr 2O 2 − 4 7 C CrO2Cl2 → CrO 2 − 4 D CrO2Cl2 → Cr2O33 / 78
Question 15: Photochromic glass, used for sunglasses, darkens when exposed to bright light and becomes more transparent again when the light is less bri…Question 16: Which statements about the reaction of solid sodium bromide with concentrated sulfuric acid are correct? 1 Hydrogen bromide is a product of…Question 17: Ammonium nitrate, NH4NO3, can decompose explosively when heated. NH4NO3 → N2O + 2H2O What are the changes in the oxidation numbers of the t…Question 18: How does concentrated sulfuric acid behave when it reacts with sodium chloride? A as an acid only B as an acid and oxidising agent C as an …Question 19: Which reactions are redox reactions? 1 CaBr2 + 2H2SO4 → CaSO4 + Br2 + SO2 + 2H2O 2 CaBr2 + 2H3PO4 → Ca(H2PO4)2 + 2HBr 3 CaBr2 + 2AgNO3 → Ca…4 / 78
Question 20: Sodium hydrogensulfide, NaSH, is used to remove hair from animal hides. Which statements about the SH– ion are correct? 1 It contains 18 el…Question 21: In a car engine, non-metallic element X forms a pollutant oxide Y. Further oxidation of Y to Z occurs in the atmosphere. In this further ox…Question 22: Sulfur dioxide and sulfites are used in food preservation. Why are they used for this purpose? 1 They are reducing agents so retard the oxi…Question 23: Ammonium nitrate, NH4NO3, can decompose explosively when heated. NH4NO3 → N2O + 2H2O What are the changes in the oxidation numbers of the t…Question 24: How does concentrated sulfuric acid behave when it reacts with sodium chloride? A as an acid only B as an acid and oxidising agent C as an …Question 25: Sodium hydrogensulfide, NaSH, is used to remove hair from animal hides. Which statements about the SH– ion are correct? 1 It contains 18 el…5 / 78
Question 26: Which reactions are redox reactions? 1 CaBr2 + 2H2SO4 → CaSO4 + Br2 + SO2 + 2H2O 2 CaBr2 + 2H3PO4 → Ca(H2PO4)2 + 2HBr 3 CaBr2 + 2AgNO3 → Ca…Question 27: In a car engine, non-metallic element X forms a pollutant oxide Y. Further oxidation of Y to Z occurs in the atmosphere. In this further ox…Question 28: Sulfur dioxide and sulfites are used in food preservation. Why are they used for this purpose? 1 They are reducing agents so retard the oxi…Question 29: Ammonium nitrate, NH4NO3, can decompose explosively when heated. NH4NO3 → N2O + 2H2O What are the changes in the oxidation numbers of the t…Question 30: How does concentrated sulfuric acid behave when it reacts with sodium chloride? A as an acid only B as an acid and oxidising agent C as an …Question 31: Which reactions are redox reactions? 1 CaBr2 + 2H2SO4 → CaSO4 + Br2 + SO2 + 2H2O 2 CaBr2 + 2H3PO4 → Ca(H2PO4)2 + 2HBr 3 CaBr2 + 2AgNO3 → Ca…6 / 78
Question 32: Sodium hydrogensulfide, NaSH, is used to remove hair from animal hides. Which statements about the SH– ion are correct? 1 It contains 18 el…Question 33: In a car engine, non-metallic element X forms a pollutant oxide Y. Further oxidation of Y to Z occurs in the atmosphere. In this further ox…Question 34: Sulfur dioxide and sulfites are used in food preservation. Why are they used for this purpose? 1 They are reducing agents so retard the oxi…Question 35: Sulfur dioxide, SO2, is added to wines to prevent oxidation of ethanol by air. To determine the amount of SO2, a sample of wine is titrated…Question 36: Ammonium sulfate in nitrogenous fertilisers in the soil can be slowly oxidised by air producing sulfuric acid, nitric acid and water. How m…Question 37: Sulfur dioxide is used to bleach wood pulp in the production of paper. It is also used as an additive in the production of jam and marmalad…7 / 78
Question 38: Disproportionation is the term used to describe a reaction in which a reactant is simultaneously both oxidised and reduced. To which incomp…Question 39: In aqueous solution, the acid HIO disproportionates according to the following equation where m, n, p and q are simple whole numbers in the…Question 40: What happens when chlorine is bubbled through aqueous potassium iodide? A Chlorine is oxidised to chlorate(V) ions. B Chlorine is oxidised …Question 41: Which pair of reagents will take part in a redox reaction? A CH3CH2OH + concentrated H2SO4 B CH3CHO + Tollens’ reagent C CH3CO2C2H5 + dilut…Question 42: Zirconium, Zr, proton number 40, is a metal which is used in corrosion-resistant alloys. Zirconium metal is extracted from the oxide ZrO2 b…8 / 78
Question 43: Sulfur dioxide, SO2, is added to wines to prevent oxidation of ethanol by air. To determine the amount of SO2, a sample of wine is titrated…Question 44: Ammonium sulfate in nitrogenous fertilisers in the soil can be slowly oxidised by air producing sulfuric acid, nitric acid and water. How m…Question 45: Disproportionation is the term used to describe a reaction in which a reactant is simultaneously both oxidised and reduced. To which incomp…Question 46: In flooded soils, like those used for rice cultivation, the oxygen content is low. In such soils, anaerobic bacteria cause the loss of nitr…Question 47: X, Y and Z represent different halogens. The table shows the results of nine experiments in which aqueous solutions of X2, Y2 and Z2 were s…9 / 78
Question 48: A student observed the reactions when sodium chloride and sodium iodide were each reacted separately with concentrated sulfuric acid and wi…Question 49: Concentrated sulfuric acid can behave both as a strong acid and as an oxidising agent. With which compound does concentrated sulfuric acid …Question 50: Which compound contains two different elements with identical oxidation states? A HCl O B Mg(OH)2 C Na2SO4 D NH4ClQuestion 51: When the yellow liquid NCl 3 is stirred into aqueous sodium hydroxide, the reaction that occurs can be represented by the following equatio…Question 52: In a car engine pollutant oxide Y, which contains non-metallic element X, is formed. Further oxidation of Y to Z occurs in the atmosphere. …10 / 78
Question 53: In flooded soils, like those used for rice cultivation, the oxygen content is low. In such soils, anaerobic bacteria cause the loss of nitr…Question 54: X, Y and Z represent different halogens. The table shows the results of nine experiments in which aqueous solutions of X2, Y2 and Z2 were s…Question 55: When chlorine and aqueous sodium hydroxide are heated together the following overall reaction occurs. 3Cl 2(aq) + 6NaOH(aq) → 5NaCl (aq) + …11 / 78
Question 56: Sulfur dioxide is used as a preservative in wine making. The following equations describe how sulfur dioxide dissolves. H2O + SO2 HSO3 – + …Question 57: Which of the halide ions, chloride, bromide or iodide, acts as a reducing agent when its sodium salt reacts with concentrated sulfuric acid…Question 58: Which pollutant, present in the exhaust fumes of an internal combustion engine, has an element in the +2 oxidation state and an odd number …Question 59: The amount of titanium dioxide in an ore can be determined by using the following reaction. 3TiO2 + 4BrF3 → 3TiF4 + 2Br2 + 3O2 Whic…Question 60: Sodium iodide reacts with concentrated sulfuric acid. The equation which represents one of the reactions that takes place is shown. 8NaI + …12 / 78
Question 61: In a car engine, non-metallic element X forms a pollutant oxide Y. Further oxidation of Y to Z occurs spontaneously in the atmosphere. In t…Question 62: Use of the Data Booklet is relevant to this question. Lead(IV) chloride will oxidise bromide ions to bromine. The Pb4+ ions are reduced to …Question 63: When chlorine and aqueous sodium hydroxide are heated together the following overall reaction occurs. 3Cl 2(aq) + 6NaOH(aq) → 5NaCl (aq) + …Question 64: Sulfur dioxide is used as a preservative in wine making. The following equations describe how sulfur dioxide dissolves. H2O + SO2 HSO3 – + …13 / 78
Question 65: Which of the halide ions, chloride, bromide or iodide, acts as a reducing agent when its sodium salt reacts with concentrated sulfuric acid…Question 66: The oxide of titanium, TiO2, is used as a ‘whitener’ in toothpaste. It is obtained from the ore iron(II) titanate, FeTiO3. What is the chan…Question 67: The diagram shows a cell for the manufacture of aluminium. graphite anodes mixture of Al 2O3 and molten cryolite graphite lining acting as …Question 68: In the treatment of domestic water supplies, chlorine is added to the water to form HCl O. Cl 2(aq) + H2O(I) → H+(aq) + Cl –(aq) + HCl O(aq…14 / 78
Question 69: Carbon monoxide, CO, nitrogen monoxide, NO, and sulfur dioxide, SO2, may all be present in the exhaust fumes from a car engine. Which react…Question 70: Ammonia and chlorine react in the gas phase. 8NH3 + 3Cl 2 → N2 + 6NH4Cl Which statements are correct? 1 Ammonia behaves as a reducing agent…Question 71: In which substance does nitrogen exhibit the highest oxidation state? A NO B N2O C N2O4 D NaNO2Question 72: Chlorine shows oxidation states ranging from –1 to +7 in its compounds. What are the reagent(s) and conditions necessary for the oxidation …Question 73: Ammonia and chlorine react in the gas phase. 8NH3 + 3Cl 2 → N2 + 6NH4Cl Which statements are correct? 1 Each nitrogen atom is oxidised. 2 E…15 / 78
Question 74: Two conversions are outlined below. NH4 + → NH3 C2H4 → C2H6 What similar feature do these two conversions have? A a lone pair of electrons …Question 75: The diagram shows a cell for the manufacture of aluminium. graphite anodes mixture of Al 2O3 and molten cryolite graphite lining acting as …Question 76: The oxide of titanium, TiO2, is used as a ‘whitener’ in toothpaste. It is obtained from the ore iron(II) titanate, FeTiO3. What is the chan…16 / 78
Question 77: In the treatment of domestic water supplies, chlorine is added to the water to form HCl O. Cl 2(aq) + H2O(I) → H+(aq) + Cl –(aq) + HCl O(aq…Question 78: Carbon monoxide, CO, nitrogen monoxide, NO, and sulfur dioxide, SO2, may all be present in the exhaust fumes from a car engine. Which react…Question 79: Ammonia and chlorine react in the gas phase. 8NH3 + 3Cl 2 → N2 + 6NH4Cl Which statements are correct? 1 Ammonia behaves as a reducing agent…Question 80: In which reaction does an element undergo the largest change in oxidation state? A Cl 2 + 2OH– → OCl – + Cl – + H2O B 3Cl 2 + 6OH– → Cl O3 …17 / 78
Question 81: In a car engine, non-metallic element X forms a pollutant oxide Y. Y can be further oxidised to Z. Two students made the following statemen…Question 82: One of the reactions taking place in a catalytic converter in a car exhaust system is between nitrogen oxide and octane (unburned petrol). …Question 83: How may nitrogen exist in compounds? 1 bonded by a triple covalent bond 2 as part of a cation 3 having lost 3 electrons to form an anionQuestion 84: In which reaction does an element undergo the largest change in oxidation state? A Cl 2 + 2OH– → OCl – + Cl – + H2O B 3Cl 2 + 6OH– → Cl O3 …18 / 78
Question 85: In a car engine, non-metallic element X forms a pollutant oxide Y. Y can be further oxidised to Z. Two students made the following statemen…Question 86: One of the reactions taking place in a catalytic converter in a car exhaust system is between nitrogen oxide and octane (unburned petrol). …Question 87: Aluminium is extracted by the electrolysis of a molten mixture containing aluminium oxide. By a similar method, magnesium is extracted by t…Question 88: The reaction between KI and concentrated H2SO4 is a redox reaction. 5H2SO4 + 8KI → 4K2SO4 + 4I2 + H2S + 4H2O What is the change i…19 / 78
Question 89: Deposits of ammonium sulfate have been discovered in areas of high atmospheric pollution. They are believed to arise from the following rea…Question 90: How may nitrogen exist in compounds? 1 bonded by a triple covalent bond 2 as part of a cation 3 in an oxidation state of +5Question 91: An element X and compound YZ react separately with acid as shown. X(s) + 2H+(aq) → X2+(aq) + H2(g) YZ(s) + 2H+(aq) → Y2+(aq) + H2Z(g) When …Question 92: Which pairs of reagents will react together in a redox reaction? 1 CH3CHO + Fehling’s reagent 2 CH4 + Cl 2 3 CH3COCH3 + Tollens’ reagent20 / 78
Question 93: Solutions containing chlorate(I) ions are used as household bleaches and disinfectants. These solutions decompose on heating as shown. 3Cl …Question 94: The diagram shows an electrolytic cell for the extraction of aluminium. graphite anode Al 2O3 in molten cryolite graphite lining acting as …Question 95: A solution of Sn2+ ions will reduce an acidified solution of MnO4 – ions to Mn2+ ions. The Sn2+ ions are oxidised to Sn4+ ions in this reac…Question 96: What happens when iodine solution is added to a solution of sodium bromide? A A reaction occurs without changes in oxidation state. B Bromi…21 / 78
Question 97: Element 85, astatine, is in Group VII. Concentrated sulfuric acid is added to sodium astatide. The mixture of products includes astatine, h…Question 98: In which reactions is the organic compound oxidised by the given reagent? 1 CH3CH2CHO + Fehling’s reagent 2 CH3CH2CH2CHO + Tollens’ rea…Question 99: During the electrolysis of molten aluminium oxide to produce aluminium, using carbon electrodes, two consecutive reactions occur at the ano…Question 100: What happens when bromine solution is added to a solution of sodium iodide? A A reaction occurs without changes in oxidation state. B Bromi…Question 101: Sulfur dioxide is an atmospheric pollutant that causes acid rain. One of the reactions in this process is the oxidation of sulfur dioxide t…22 / 78
Question 102: In the redox reaction shown, how do the oxidation states of vanadium and sulfur change? VO2 + + SO2 → V3+ + SO4 2– vanadium sulfur fr…Question 103: A space shuttle’s upward thrust came from the following reaction between aluminium and ammonium perchlorate. 10Al + 6NH4Cl O4 → 4Al 2O3…Question 104: In which reaction does a single nitrogen atom have the greatest change in oxidation number? A 4NH3 + 5O2 → 4NO + 6H2O B 3NO2 + H2O …Question 105: The following half reactions occur when potassium iodate(V), KIO3, in hydrochloric acid solution oxidises iodine to ICl 2 –. IO3 – + 2Cl …23 / 78
Question 106: Solid potassium halides react with concentrated sulfuric acid, according to the following equations. reaction 1 2KCl + H2SO4 → K2SO4 +…Question 107: Primary alcohols can be oxidised to aldehydes using either acidified potassium dichromate(VI) or acidified potassium manganate(VII). Both t…Question 108: In which reaction is the organic compound oxidised? A CH3CH2OH + concentrated H3PO4 B CH3CH2CH2CHO + Tollens’ reagent C CH3COCH3 + 2,…Question 109: Sulfur dioxide and sulfites are used in food preservation. Why are they used for this purpose? 1 They are reducing agents which slow down t…24 / 78
Question 110: In which reaction does a single nitrogen atom have the greatest change in oxidation number? A 4NH3 + 5O2 → 4NO + 6H2O B 3NO2 + H2O …Question 111: The following half reactions occur when potassium iodate(V), KIO3, in hydrochloric acid solution oxidises iodine to ICl 2 –. IO3 – + 2Cl …Question 112: Solid potassium halides react with concentrated sulfuric acid, according to the following equations. reaction 1 2KCl + H2SO4 → K2SO4 +…Question 113: Primary alcohols can be oxidised to aldehydes using either acidified potassium dichromate(VI) or acidified potassium manganate(VII). Both t…25 / 78
Question 114: In which reaction is the organic compound oxidised? A CH3CH2OH + concentrated H3PO4 B CH3CH2CH2CHO + Tollens’ reagent C CH3COCH3 + 2,…Question 115: Sulfur dioxide and sulfites are used in food preservation. Why are they used for this purpose? 1 They are reducing agents which slow down t…Question 116: Ammonium nitrate, NH4NO3, can decompose explosively when heated. NH4NO3 → N2O + 2H2O What are the changes in the oxidation numbers of t…Question 117: A 10 cm3 sample of 0.30 mol dm–3 Tl +NO3 – required 20 cm3 of 0.10 mol dm–3 acidified NH4VO3 to oxidise it to Tl 3+ in solution. Vanadium i…Question 118: The Contact process is used in the manufacture of sulfuric acid. The equation for the main reaction is shown below. 2SO2(g) + O2(g) 2SO3(…Question 119: Redox reactions occur very frequently in the chemistry of Group VII. Which statement is correct? A Chlorine will oxidise bromide ions but n…26 / 78
Question 120: Pollutant oxide Y, which contains non-metallic element X, is formed in a car engine. Further oxidation of Y to Z occurs in the atmosphere. …Question 121: In which reaction is the species in bold acting as an oxidising agent? A 2Ca + O2 → 2CaO B Cr2O7 2– + 8H+ + 3SO3 2– → 2Cr3+ + 4…Question 122: Ammonium sulfate in the soil is slowly oxidised by air, producing sulfuric acid, nitric acid and water as the only products. How many moles…Question 123: When solid sodium iodide reacts with concentrated sulfuric acid, the products include NaHSO4, H2S, SO2 and S. In the formation of which pro…Question 124: Menthol is a naturally-occurring alcohol found in peppermint oil. OH menthol Which reagents will react with menthol? 1 aqueous bromine 2 so…27 / 78
Question 125: Which pairs of reagents will take part in a redox reaction under suitable conditions? 1 CH3(CH2)4CHO + Tollens’ reagent 2 CH3(CH2)4CH3 +…Question 126: The free radical substitution reaction between methane and chlorine involves initiation, propagation and termination stages. Which row is c…Question 127: Many crude oils contain H2S. During refining, by the Claus process, the H2S is converted into solid sulfur, which is then removed. reaction…Question 128: Which statements explain why sulfur dioxide is used as a food preservative? 1 It is a reducing agent and therefore an anti-oxidant. 2 It pr…Question 129: In which reaction does hydrogen behave as an oxidising agent? A H2 + Cl 2 → 2HCl B C2H4 + H2 → C2H6 C N2 + 3H2 → 2NH3 D 2Na + …28 / 78
Question 130: Which property is not associated with the element sodium? A It can react with cold water to form hydrogen. B It forms a basic oxide. C It f…Question 131: Chlorine gas reacts with cold aqueous sodium hydroxide. It can also react with hot aqueous sodium hydroxide. What are the oxidation numbers…Question 132: In which reaction does hydrogen behave as an oxidising agent? A H2 + Cl 2 → 2HCl B C2H4 + H2 → C2H6 C N2 + 3H2 → 2NH3 D 2Na + …Question 133: Chlorine gas reacts with cold aqueous sodium hydroxide. It can also react with hot aqueous sodium hydroxide. What are the oxidation numbers…Question 134: Under standard conditions, which statement is correct? A Cl –(aq) can oxidise Br2(aq). B Cl –(aq) can reduce Br2(aq). C Cl 2(aq) can oxidis…29 / 78
Question 135: Use of the Data Booklet is relevant to this question. Ferrochrome is an alloy of iron and chromium. Ferrochrome can be dissolved in dilute …Question 136: In a solution that contains both Br2 and Cl 2, a process takes place that produces BrO3 – ions. The process is represented by the following…Question 137: In oxygen difluoride, OF2, fluorine has an oxidation number of –1. OF2 will react with sulfur dioxide according to the following equation. …30 / 78
Question 138: Photochromic glass, used for sunglasses, darkens when exposed to bright light and becomes more transparent again when the light is less bri…Question 139: Carbon monoxide, CO, nitrogen dioxide, NO2, and sulfur dioxide, SO2, are all atmospheric pollutants. Which reaction concerning these compou…Question 140: Chlorate(V) ions, Cl O3 –, are produced in the redox reaction between chlorine and hot aqueous sodium hydroxide. Oxidation numbers can be u…Question 141: Which of these reactions are redox reactions? 1 6NO(g) + 4NH3(g) → 5N2(g) + 6H2O(g) 2 2SO2(g) + O2(g) → 2SO3(g) 3 SO3(g) + H2O(…31 / 78
Question 142: Arsenic chloride, AsCl 3, reacts with sodium borohydride, NaBH4. pAsCl 3 + qNaBH4 → rAsH3 + sNaCl + tBCl 3 What are the numbers p, …Question 143: Calcium forms an ionic compound with carbon, called calcium carbide. The oxidation number of carbon in calcium carbide is –1. Calcium carbi…Question 144: Ammonia and chlorine react in the gas phase. 8NH3 + 3Cl 2 → N2 + 6NH4Cl Which statements are correct? 1 Each nitrogen atom is oxidise…Question 145: Which compound contains two different elements with identical oxidation states? A HCl O B Mg(OH)2 C Na2SO4 D NH4ClQuestion 146: After black and white photographic film has been developed, unreacted silver bromide is removed by reaction with sodium thiosulfate. AgBr …32 / 78
Question 147: A sample containing 0.40 mol of calcium nitrate was decomposed by heating in a roaring Bunsen burner flame until there was no further decom…Question 148: Which pair of reagents will take part in a redox reaction? A CH3CHCH2 + Br2 B CH3CH2CH2OH + concentrated H3PO4 C CH3COCH3 + HCN D HCO…Question 149: Bromine reacts with water. Br2 + H2O HOBr + HBr Which oxidation states of bromine are present in the equilibrium mixture? 1 +3 2 0 3 –1Question 150: In the treatment of domestic water supplies, chlorine is added to the water to form HCl O. Cl 2(aq) + H2O(I) → H+(aq) + Cl –(aq) + …33 / 78
Question 151: Nitrogen(II) oxide, NO, nitrogen(IV) oxide, NO2, carbon monoxide, CO, and unburnt hydrocarbons are present in the exhaust gases of internal…Question 152: In which reaction is the organic compound oxidised? A CH3CH2CH2CHO + Tollens’ reagent B CH3CH2CH2CHO + LiAl H4 C CH3CH2CH2OH + concen…Question 153: Sulfur dioxide is used as a preservative in wine making. The following equations describe the reactions that occur when sulfur dioxide diss…Question 154: When KCl O3 is heated, the following reaction occurs. 4KCl O3 → 3KCl O4 + KCl Which statements are correct? 1 The oxidation state of Cl…34 / 78
Question 155: The reaction between acidified dichromate(VI) ions, Cr2O7 2–, and aqueous Fe2+ ions results in the dichromate(VI) ions being reduced to Cr3…Question 156: Sodium chromate(VI), Na2CrO4, is manufactured by heating chromite, FeCr2O4, with sodium carbonate in an oxidising atmosphere. Chromite cont…Question 157: X, Y and Z represent different halogens. The table shows the results of nine experiments in which aqueous solutions of X2, Y2 and Z2 were s…Question 158: The reaction between acidified dichromate(VI) ions, Cr2O7 2–, and aqueous Fe2+ ions results in the dichromate(VI) ions being reduced to Cr3…35 / 78
Question 159: Sodium chromate(VI), Na2CrO4, is manufactured by heating chromite, FeCr2O4, with sodium carbonate in an oxidising atmosphere. Chromite cont…Question 160: X, Y and Z represent different halogens. The table shows the results of nine experiments in which aqueous solutions of X2, Y2 and Z2 were s…Question 161: In some fireworks there is a reaction between powdered aluminium and powdered barium nitrate. Heat is evolved, an unreactive gas is produce…36 / 78
Question 162: A reaction sequence is shown. 1 2 3 4 SO2 SO3 H2SO4 H2S SO2 In each stage of this sequence the sulfur is oxidised, reduced or neither oxidi…Question 163: Element X reacts with cold, dilute, aqueous sodium hydroxide to form two different chlorine-containing products, Y and Z. What are the oxid…Question 164: Two conversions are shown. NH4 + → NH3 C2H4 → C2H6 Which similar feature do these two conversions have? A change in oxidation state of an e…Question 165: Vanadium reacts with dilute sulfuric acid to form V2(SO4)3 and hydrogen gas. What happens to vanadium atoms in this reaction? A They lose t…37 / 78
Question 166: Na2S2O3 reacts with HCl as shown. Na2S2O3(aq) + 2HCl (aq) → 2NaCl (aq) + H2O(l) + SO2(g) + S(s) When calculating the oxidation nu…Question 167: Which row correctly describes the reactions of calcium and strontium with water? substance reduced substance oxidised more vigorous reactio…Question 168: Chlorine gas is added to cold, aqueous sodium hydroxide. In a separate experiment, chlorine gas is added to hot, aqueous sodium hydroxide. …Question 169: Which statements about the atoms 23Na and 24Mg are correct? 1 They have the same number of filled electron orbitals. 2 They have the same n…38 / 78
Question 170: One of the reactions in a lead / acid cell is shown. Pb(s) + PbO2(s) + 4H+(aq) + 2SO4 2–(aq) → 2PbSO4(s) + 2H2O(l) Which statemen…Question 171: 71.0 g of chlorine, Cl 2, react with an excess of sodium hydroxide solution at a particular temperature. The reaction produces exactly 35.5…Question 172: One way of recovering tin from old printed circuit boards is to dissolve it in a mixture of concentrated hydrochloric acid and concentrated…Question 173: Which statement is always correct for an oxidation reaction? A It involves the gain of oxygen by an element. B For one reactant to be oxidi…Question 174: Hydrogen sulfide can be oxidised to form sulfur dioxide. 2H2S + 3O2 → 2SO2 + 2H2O Which statements are correct? 1 The oxidation numbe…39 / 78
Question 175: Modern cars are fitted with catalytic converters to reduce atmospheric pollution caused by unwanted reactions during the combustion of the …Question 176: One of the reactions in a lead / acid cell is shown. Pb(s) + PbO2(s) + 4H+(aq) + 2SO4 2–(aq) → 2PbSO4(s) + 2H2O(l) Which statemen…Question 177: One way of recovering tin from old printed circuit boards is to dissolve it in a mixture of concentrated hydrochloric acid and concentrated…Question 178: Which reaction is not a redox reaction? A Mg + 2HNO3 → Mg(NO3)2 + H2 B 2Mg(NO3)2 → 2MgO + 4NO2 + O2 C SO2 + NO2 → SO3 + N…40 / 78
Question 179: Bromine is extracted from sea-water. In the final stages of the process two redox reactions take place. Br2(aq) + SO2(g) + 2H2O(l) → …Question 180: When burned, sulfur forms a gaseous product X which can be oxidised to produce a gas Y. Gas Y reacts with water to produce a product Z. Whi…Question 181: Ammonia and chlorine react together in the gas phase. 8NH3 + 3Cl 2 → N2 + 6NH4Cl Which statements are correct? 1 Ammonia behaves as a…Question 182: Chlorine reacts with hot aqueous sodium hydroxide. Which oxidation states does chlorine show in the products of this reaction? 1 –1 2 +3 3 …Question 183: In which different forms does nitrogen exist in compounds? 1 bonded by a triple covalent bond 2 as part of a cation 3 in an oxidation state…41 / 78
Question 184: Ethanedioate ions, C2O4 2–, react with a suitable reagent to form CO2. A half-equation for this reaction is shown. C2O4 2– → 2CO2 + 2e–…Question 185: Oxidation numbers should be used to answer this question. A redox reaction takes place between hydroxylammonium ions, [NH3OH]+, and acidifi…Question 186: Chlorine reacts with cold aqueous sodium hydroxide to produce sodium chloride, water and compound X. Chlorine reacts with hot aqueous sodiu…Question 187: Each of the three mixtures shown can result in a chemical reaction. Which mixtures result in a redox reaction? 1 bromine + hydrogen 2 sodiu…42 / 78
Question 188: Sulfur reacts with concentrated nitric acid in a redox reaction. S + 4HNO3 → SO2 + 4NO2 + 2H2O What are the changes in oxidation nu…Question 189: Xenon hexafluoride, XeF6, reacts with water. XeF6 + 3H2O → XeO3 + 6HF Which statement is correct? A Hydrogen is reduced in this react…Question 190: When calcium and calcium hydride, CaH2, react separately with water, they each produce a white solid and a colourless gas. The white solid …Question 191: When concentrated sulfuric acid is added to solid sodium chloride, HCl is formed but not Cl 2. When concentrated sulfuric acid is added to …43 / 78
Question 192: Ammonia and chlorine react as shown. 8NH3 + 3Cl 2 → N2 + 6NH4Cl Which statements are correct? 1 Each nitrogen atom is oxidised. 2 Eac…Question 193: Nitric acid is known to take part in the oxidation of atmospheric sulfur dioxide. One possible reaction is shown. SO2 + HNO3 → NO+ + …Question 194: A transition metal ion, M2+, reacts with acidified dichromate(VI) ions to form M4+ ions, Cr3+ ions, and H2O. Which equation correctly repre…Question 195: Reaction 1: chlorine reacts with cold aqueous sodium hydroxide to form solution Z. Reaction 2: solution Z is heated and forms Cl O3 –(aq) a…44 / 78
Question 196: Ammonium metavanadate, NH4VO3, can be used to make a solution containing VO2Cl, which contains chloride ions. What is the change in the oxi…Question 197: Chlorine reacts with both hot and cold sodium hydroxide to form products containing chlorine. Cold sodium hydroxide forms sodium chlorate(X…Question 198: Aqueous iron(II) sulfate can take part in redox reactions. 6FeSO4 + 7H2SO4 + Na2Cr2O7 → 3Fe2(SO4)3 + Cr2(SO4)3 + Na2SO4 + 7H2O …Question 199: Nitric acid is known to take part in the oxidation of atmospheric sulfur dioxide. One possible reaction is shown. SO2 + HNO3 → NO+ + …Question 200: A transition metal ion, M2+, reacts with acidified dichromate(VI) ions to form M4+ ions, Cr3+ ions, and H2O. Which equation correctly repre…45 / 78
Question 201: Reaction 1: chlorine reacts with cold aqueous sodium hydroxide to form solution Z. Reaction 2: solution Z is heated and forms Cl O3 –(aq) a…Question 202: Acidified potassium manganate(VII) reacts with iron(II) ethanedioate, FeC2O4. The reactions taking place are shown. MnO4 – + 8H+ + 5e– …Question 203: Under standard conditions, which statement is correct? A Cl 2(aq) can oxidise Br –(aq). B Cl 2(aq) can reduce Br –(aq). C Cl –(aq) can oxid…Question 204: Ammonia, NH3, and hydrazine, NH2NH2, are two compounds of nitrogen, N2. Which statement is correct? A The N–N bond in NH2NH2 is polar. B NH…Question 205: In which reactions is the underlined element or compound reduced? 1 NaCl O + H2O2 → O2 + NaCl + H2O 2 2NH3 + 2Li → 2LiNH2 + H…46 / 78
Question 206: Ethanedioic acid, HO2CCO2H, can be oxidised by KMnO4 in dilute sulfuric acid. The products of this reaction are carbon dioxide, water, pota…Question 207: Concentrated sulfuric acid is added to separate solid samples of sodium chloride, sodium bromide and sodium iodide. With which samples does…Question 208: X is either chlorine or an oxide of chlorine. X reacts with water, under suitable conditions, to form the two acids HCl and HCl O3 in the m…Question 209: Which reaction gives a product that is an atmospheric pollutant causing acid rain? A 3Mg(s) + SO2(g) → MgS(s) + 2MgO(s) B (NH4)2SO4(s…Question 210: When O2 reacts with H2S the products are SO2 and H2O. Mixture Y contains an equal number of the two molecules shown, and no other molecules…47 / 78
Question 211: In which reactions are nitrogen atoms reduced? 1 2NO2 → N2 + 2O2 2 4NO2 → 2N2O + 3O2 3 4NO2 + 6H2O → 4NH3 + 7O2Question 212: A small quantity of hot, concentrated sulfuric acid is added separately to solid samples of potassium halides, KX. Which potassium halides …Question 213: Manganese and nitrogen can show a range of different oxidation states. Calculate the sum of the oxidation states of Mn and N in each row of…Question 214: Ethanol can be oxidised to ethanal by dilute acidified dichromate(VI) ions. The oxidation reaction equation is C2H5OH → C2H4O + 2H+ + …Question 215: What is the oxidation number of sulfur in each species? H2S SO2 H2SO3 A –2 +4 +4 B –2 +4 +6 C +2 –4 +4 D +2 –4 +648 / 78
Question 216: In the chemical equation, w, x, y and z are all whole numbers. wCl O3 – + xMnO4 – + yH+ → wCl O4 – + xMnO2 + zH2O When the equati…Question 217: (NH4)2Cr2O7 decomposes when heated. (NH4)2Cr2O7 → N2 + 4H2O + Cr2O3 Which element is oxidised and which element is reduced? oxidised …Question 218: When lead(II) sulfide, PbS, is heated in air, sulfur dioxide and lead(II) oxide are formed. What is the equation for the reaction between P…Question 219: Chlorate(V) ions, Cl O3 –, are produced in the redox reaction between chlorine and hot aqueous sodium hydroxide. Oxidation numbers can be u…49 / 78
Question 220: Solid sodium iodide reacts with concentrated sulfuric acid to form more than one product that contains sulfur. What is the lowest oxidation…Question 221: What is the oxidation number of sulfur in each species? H2S SO2 H2SO3 A –2 +4 +4 B –2 +4 +6 C +2 –4 +4 D +2 –4 +6Question 222: In the chemical equation, w, x, y and z are all whole numbers. wCl O3 – + xMnO4 – + yH+ → wCl O4 – + xMnO2 + zH2O When the equati…Question 223: In the redox reaction shown, how do the oxidation states of vanadium and sulfur change? VO2 + + SO2 → V3+ + SO4 2– vanadium sulfur fr…Question 224: When the equation is correctly balanced, what is the value of c? aC2H4 + bH2O + cH+ + 2MnO4 – → dC2H6O2 + eMn2+ A 3 B 4 C 5 D 650 / 78
Question 225: Hot aqueous sodium hydroxide reacts with chlorine. 6NaOH(aq) + 3Cl 2(g) → 5NaCl (aq) + NaCl O3(aq) + 3H2O(I) Which statement is cor…Question 226: How does concentrated sulfuric acid behave when it reacts with sodium chloride? A as an acid only B as an acid and oxidising agent C as an …Question 227: Cobalt can form the positive ion Co(NH3)4Cl 2 +. What is the oxidation number of cobalt in this ion? A +1 B +2 C +3 D +6Question 228: In this question you should use changes in oxidation numbers to balance a chemical equation. Acidified potassium dichromate(VI) solution ca…Question 229: Carbon monoxide burns readily in oxygen to form carbon dioxide. What does this information suggest? 1 The +4 oxidation state of carbon is m…Question 230: The catalytic converters fitted to cars remove pollutants from the exhaust gases. Some of the reactions that occur involve oxygen, which co…51 / 78
Question 231: Chlorine reacts with sodium hydroxide in two different ways depending upon the temperature. reaction 1 Cl 2 + 2OH– → Cl – + Cl O– + …Question 232: In which of the reactions is the organic compound oxidised by the given reagent? 1 CH3CHO + HCN reagent 2 CH3CH2CH2CHO + Tollens’ reage…Question 233: In this question you should use changes in oxidation numbers to balance a chemical equation. The following reaction occurs when MnO2 is war…Question 234: In which reaction does an element undergo the largest change in oxidation number? A Cl 2 + 2OH– → OCl – + Cl – + H2O B 3Cl 2 + 6O…Question 235: Nitrogen reacts with oxygen to form nitrogen monoxide, NO, and nitrogen dioxide, NO2. Nitrogen dioxide reacts with water and with hydroxide…52 / 78
Question 236: When solid KCl O3 is heated in the absence of air, a mixture of two chlorine compounds in the mole ratio of 3 : 1 is formed. Chlorine is th…Question 237: Which element, when burned in oxygen, can form an oxide that is a reducing agent? A Na B Mg C Al D SQuestion 238: Nitrogen oxides are removed from the exhaust gases of internal combustion engines by the action of a catalyst in a catalytic converter. Whi…Question 239: In which reaction does the greatest change in the oxidation number of sulfur occur? A S(s) + O2(g)  SO2(g) B SO2(g) + 2 1O2(g) SO3(g…Question 240: The first stage in the chloride process for the manufacture of titanium consists of the following reaction. 2TiO2 + 4Cl 2 + 3C  2TiC…Question 241: With which compound does concentrated sulfuric acid react both as a strong acid and as an oxidising agent? A magnesium carbonate B potassiu…53 / 78
Question 242: Nitrogen forms a number of oxides. Their enthalpies of formation are given. [NO(g)] = +90 kJ mol–1 [N2O(g)] = +82 kJ mol–1 [NO2(g)] = +33 k…Question 243: What is the average oxidation number of sulfur in each compound? Ca(HSO3)2 Na2S2O3 A 4 2 B 4 4 C 6 2 D 6 4Question 244: Chlorine dioxide, Cl O2, reacts with sodium hydroxide in the reaction shown. 2Cl O2 + 2OH– → Cl O2 – + Cl O3 – + H2O Which statemen…Question 245: In which reaction does the greatest change in the oxidation number of sulfur occur? A S(s) + O2(g)  SO2(g) B SO2(g) + 2 1O2(g) SO3(g…Question 246: The first stage in the chloride process for the manufacture of titanium consists of the following reaction. 2TiO2 + 4Cl 2 + 3C  2TiC…54 / 78
Question 247: With which compound does concentrated sulfuric acid react both as a strong acid and as an oxidising agent? A magnesium carbonate B potassiu…Question 248: Nitrogen forms a number of oxides. Their enthalpies of formation are given. [NO(g)] = +90 kJ mol–1 [N2O(g)] = +82 kJ mol–1 [NO2(g)] = +33 k…Question 249: VO2Cl reacts with NaI under acidic conditions. 2VO2Cl + 2H2SO4 + 2NaI  VOCl 2 + VOSO4 + I2 + Na2SO4 + 2H2O The oxidation sta…Question 250: Chlorine gas is reacted with aqueous sodium hydroxide. The oxidation number of chlorine changes from 0 to –1 and also from 0 to +1. Under w…55 / 78
Question 251: When concentrated sulfuric acid reacts with sodium iodide the products include sulfur, iodine, hydrogen sulfide and sulfur dioxide. Which s…Question 252: NO, NO2, CO and unburnt hydrocarbons are present in the exhaust gases of internal combustion engines. When catalytic converters are used to…Question 253: When hydrogen iodide is reacted with concentrated sulfuric acid, several reactions occur, including: 8HI + H2SO4  H2S + 4H2O + 4I2…56 / 78
Question 254: When an organic compound is oxidised, any oxygen atom gained by the organic molecule is considered to be from a water molecule also produci…Question 255: The equation for a redox reaction is shown. SnCl 2(aq) + 2HgCl 2(aq)  SnCl 4(aq) + Hg2Cl 2(s) Which species is being oxidised in thi…Question 256: Copper dissolves in dilute nitric acid producing a blue solution of Cu(NO3)2, water and nitrogen(II) oxide as the only products. How many m…Question 257: Two reactions are shown. Only one product is identified in each reaction. ethanol + acidified Cr2O7 2–  ethanal ethanol + sodium  …57 / 78
Question 258: The equation shows the decomposition of three moles of an ion containing chromium in an acid solution. 3CrO4 3–(aq) + 8H+(aq)  2CrO4 2…Question 259: Zinc atoms can be oxidised to Zn2+ ions by dichromate(VI) ions in acid solution. Chromium is reduced to Cr3+ in this reaction. Which equati…Question 260: Z is a compound of sodium, chlorine and oxygen. It contains 45.1% by mass of oxygen. Z is prepared by reacting sodium hydroxide with chlori…Question 261: Which statements about calcium oxide are correct? 1 It can be reduced by heating with magnesium. 2 It is produced when calcium nitrate is h…Question 262: In a catalytic converter in the exhaust system of a car, carbon monoxide is oxidised to carbon dioxide, and nitrogen monoxide is reduced to…58 / 78
Question 263: Redox reactions are common in the chemistry of Group 17 elements. Which statement is correct? A Br – ions will reduce Cl 2 but not I2. B Cl…Question 264: Which reactions are redox reactions? 1 Mg + 2HCl  MgCl 2 + H2 2 2K2CrO4 + 2H+  K2Cr2O7 + 2K+ + H2O 3 CuCO3 + 2HCl  CuC…Question 265: Zinc atoms can be oxidised to Zn2+ ions by dichromate(VI) ions in acid solution. Chromium is reduced to Cr3+ in this reaction. Which equati…Question 266: Z is a compound of sodium, chlorine and oxygen. It contains 45.1% by mass of oxygen. Z is prepared by reacting sodium hydroxide with chlori…Question 267: Which statements about calcium oxide are correct? 1 It can be reduced by heating with magnesium. 2 It is produced when calcium nitrate is h…59 / 78
Question 268: A student reacts 1 mol of copper with concentrated nitric acid to produce 1 mol of copper(II) nitrate, 2 mol of water and substance X. No o…Question 269: A student reacts 4 mol of ammonia with oxygen to produce an oxide of nitrogen and water only. Each nitrogen atom increases its oxidation st…Question 270: In the treatment of domestic water supplies, chlorine is added to water to kill bacteria. Some Cl O– ions are formed. What is the change in…Question 271: Solid sodium iodide reacts with concentrated sulfuric acid to form more than one product that contains sulfur. What is the lowest oxidation…Question 272: In a catalytic converter, 5.6 g of carbon monoxide react with an excess of nitrogen monoxide. What is produced in this reaction? A 2.4 g of…Question 273: Carbon monoxide, CO, nitrogen dioxide, NO2, and sulfur dioxide, SO2, are all atmospheric pollutants. Which reaction occurs in the atmospher…60 / 78
Question 274: NCl 3 reacts with H2O. NCl 3 + 3H2O  NH3 + 3HCl O The oxidation state of nitrogen does not change in this reaction. Which statement …Question 275: In which row do the oxidation numbers of vanadium increase? smallest largest A VO4 3– VO3 – VO2 + B VO2+ V2O3 VO4 3– C V2O3 VO2+ VO3 – D VO…Question 276: Chlorine reacts with aqueous sodium hydroxide forming two chlorine-containing products. Which row shows the oxidation states of chlorine in…Question 277: A catalytic converter reduces the amount of pollutants in the fumes from a car exhaust. Which row identifies a pollutant and shows how it i…61 / 78
Question 278: Solid R is added to a solution of ammonium nitrate and the mixture is heated. A gas is given off which turns red litmus to blue. What could…Question 279: Which reaction is a redox reaction? A ethanenitrile heated under reflux with dilute hydrochloric acid B ethanoic acid reacted with aqueous …Question 280: NH4NO3 decomposes into N2O and H2O on heating. Which statements are correct? 1 The ammonium ion is behaving as a reducing agent. 2 The nitr…Question 281: A student adds 3 mol of acidified K2Cr2O7 to an excess of I– ions. The chromium is all reduced to Cr3+ and I– ions are oxidised to I2. The …Question 282: Ammonium ions are converted into nitrate ions by bacteria. What is the change in the oxidation number of nitrogen? A –6 B +6 C +8 D +962 / 78
Question 283: Sodium dichromate(VI), Na2Cr2O7, reacts with hydrogen peroxide, H2O2, producing Cr3+ ions, water and oxygen. What is the correctly balanced…Question 284: Which pair of reagents react together in a redox reaction? A CH3CHCH2 + Br2 B CH3CH2CH2OH + concentrated H3PO4 C CH3COCH3 + HCN D HCO…Question 285: Two moles of VO2 + ions react with one mole of zinc atoms in the presence of dilute acid. The products include Zn2+ ions and an ion, Y. Ion…Question 286: The compound potassium bismuthate(V), KBiO3, is a powerful oxidising agent. What is the significance of the (V) in potassium bismuthate(V)?…Question 287: What is the oxidation state of the chlorine-containing species that kills bacteria in drinking water? A –1 B +1 C +3 D +5Question 288: Ammonium ions are converted into nitrate ions by bacteria. What is the change in the oxidation number of nitrogen? A –6 B +6 C +8 D +963 / 78
Question 289: Sodium dichromate(VI), Na2Cr2O7, reacts with hydrogen peroxide, H2O2, producing Cr3+ ions, water and oxygen. What is the correctly balanced…Question 290: Which pair of reagents react together in a redox reaction? A CH3CHCH2 + Br2 B CH3CH2CH2OH + concentrated H3PO4 C CH3COCH3 + HCN D HCO…Question 291: Four equations representing reactions of nitrogen or one of its compounds are given. Which equation represents a disproportionation reactio…Question 292: The ore psilomelane may be considered to have the general formula Ba(Mnx+)(Mny+)8O16(OH)4. In this general formula, x+ and y+ are the two d…Question 293: Silicon reacts with a mixture of calcium oxide and magnesium oxide at 1200 °C. 2MgO + 2CaO + Si →2Mg + Ca2SiO4 Which statement about this r…64 / 78
Question 294: Exhaust gases from an internal combustion engine are made less harmful by passing them through a catalytic converter. A number of reactions…Question 295: The ionic equation shows iodide ions reacting with manganate(VII) ions in acidic solution. – + vH+ + wI – →xMn2+ + yH2O + zI2 uMnO4 The let…Question 296: Electronegativity differences can be used to help determine the oxidation number of an atom in different species. A number of rules are use…Question 297: Which particle contains nitrogen in the same oxidation state as in the ion N2O2 2–? A NH2F B N2O4 C NO3 – D HNF265 / 78
Question 298: HOCl(aq) is the molecule that kills bacteria when chlorine is added to water. The following reaction produces this molecule. Cl 2(g) + H2O(…Question 299: Which row correctly describes the separate reactions of calcium and strontium with water? substance reduced substance oxidised more vigorou…Question 300: Zinc reacts with concentrated nitric acid giving three products only: zinc nitrate, an oxide of nitrogen and water. 3.0 moles of zinc react…Question 301: Chlorine reacts with sodium bromide. Cl 2 + NaBr →NaCl + Br2 Which words correctly describe this reaction? 1 redox 2 displacement 3 disprop…66 / 78
Question 302: The equation for the reaction between aqueous copper ions and aqueous iodide ions is as follows. 2Cu2+(aq) + 4I–(aq) →2CuI(s) + I2(aq) What…Question 303: Q is a mixture of two compounds of Group 2 elements. Q undergoes thermal decomposition to produce a white solid and only two gaseous produc…Question 304: When concentrated sulfuric acid is added to solid sodium chloride, HCl is formed but not Cl 2. When concentrated sulfuric acid is added to …Question 305: HOCl(aq) is the molecule that kills bacteria when chlorine is added to water. The following reaction produces this molecule. Cl 2(g) + H2O(…67 / 78
Question 306: Which row correctly describes the separate reactions of calcium and strontium with water? substance reduced substance oxidised more vigorou…Question 307: One of the reactions in the rechargeable lead / acid battery is shown. Pb(s) + PbO2(s) + 4H+(aq) + 2SO4 2–(aq)  2PbSO4(s) + 2H2O…Question 308: KMnO4 is an oxidising agent. Its reaction with Fe2+ is shown in the following ionic equation. ...X...MnO4 – + ......Fe2+ + ......H+  …Question 309: The equations for three reactions involving chlorine or its compounds are listed. 1 2KCl O3  2KCl + 3O2 2 4KCl O3  3KCl O4 + KCl …68 / 78
Question 310: Nitrogen monoxide, NO, is a primary pollutant produced by petrol engines and is found in their exhaust gases. Which reaction occurs in a ca…Question 311: Sodium chromate(VI), Na2CrO4, is manufactured by heating chromite, FeCr2O4, with sodium carbonate in an oxidising atmosphere. Chromite cont…Question 312: Oxygen can be prepared by the reaction of potassium manganate(VII), KMnO4, hydrogen peroxide, H2O2, and sulfuric acid, H2SO4. Each H2O2 mol…Question 313: A solid sodium halide, NaX, is reacted with concentrated sulfuric acid. The lowest oxidation state of sulfur in the products is +4. Halogen…69 / 78
Question 314: In which pairs are both species free radicals? 1 Cl and O 2 Cl – and O2– 3 Cl and O– 4 Cl + and O2+ A 1, 3 and 4 B 1 and 3 only C 1 only D …Question 315: Nitrogen dioxide reacts with water. 2NO2 + H2O  HNO2 + HNO3 Which statement about this reaction is correct? A Both products are form…Question 316: Phosphorus reacts with concentrated sulfuric acid to produce phosphoric acid, sulfur dioxide and water. aH2SO4 + bP  cH3PO4 + dSO2 …Question 317: Chlorine gas is reacted with cold aqueous sodium hydroxide. Which statement is correct for this reaction? A Chlorine is both oxidised and r…Question 318: In which reaction does the oxidation number of chlorine change by the largest amount? A 2KCl O3  2KCl + 3O2 B 2Cl O–  Cl – + Cl O…70 / 78
Question 319: W moles of HNO2 undergoes a disproportionation reaction to produce U moles of HNO3 and V moles of NO. ● No other nitrogen containing produc…Question 320: ICl is made when Cl 2 and I2 react together. Cl 2 + I2 2ICl ICl reacts with water. 5ICl + 3H2O  5HCl + HIO3 + 2I2 Which row is c…Question 321: In alkaline solution, MnO4 – ions oxidise SO3 2– ions to SO4 2– ions. The MnO4 – ions are reduced to MnO2. What is the ratio of the two ion…Question 322: Which species contains a different number of electrons from the other three? A Cl O4 – B H2SO4 C SO4 2– D Te2–71 / 78
Question 323: Equations for some reactions of hydrogen peroxide are given. 1 2Fe2+ + H2O2 + 2H+  2Fe3+ + 2H2O 2 2MnO4 – + 5H2O2 + 6H+  2M…Question 324: The equation for the reaction of aqueous thiosulfate ions, S2O3 2–, and aqueous dioxo-vanadium ions, VO2 +, is shown. 2S2O3 2– + xVO2 + …Question 325: The name ‘chlorate’ is used for an anion consisting of chlorine and oxygen only. In a molecule of ICl, the iodine atom has oxidation number…72 / 78
Question 326: In alkaline solution, MnO4 – ions oxidise SO3 2– ions to SO4 2– ions. The MnO4 – ions are reduced to MnO2. What is the ratio of the two ion…Question 327: The equation for a reaction of KCl O3 is shown. 4KCl O3  KCl + 3KCl O4 Which row is correct? disproportionation oxidation number react…Question 328: Copper reacts with nitric acid under certain conditions. The products are copper(II) nitrate, water and an oxide of nitrogen. 3 mol of copp…Question 329: U, V and W represent different halogens. The table shows the results of nine experiments in which aqueous solutions of U2, V2 and W2 were s…73 / 78
Question 330: Two nitrates decompose on heating according to the equations shown. 2Pb(NO3)2(s)  2PbO(s) + 4NO2(g) + O2(g) 2NH4NO3(s)  2N2(g) +…Question 331: ICl3 reacts with water in a redox reaction. vICl3 + wH2O xHCl + yHI + zHIO3 + zHClO3 What are the numbers v, x and z in the corre…Question 332: A reaction involving ammonium ions is shown. NH4 + + OH– NH3 + H2O Four statements about this reaction are listed. 1 The ammonium ions …74 / 78
Question 333: Which reagent or reagents and conditions will oxidise chlorine, Cl2, into a compound containing chlorine in the +5 oxidation state? A AgNO3…Question 334: ‘Red lead’ is a red pigment with the formula Pb3O4. Every formula unit of ‘red lead’ is the same. Each formula unit contains three lead ion…Question 335: Sodium bromide is warmed with concentrated sulfuric acid. Which row describes the change in the oxidation number of the sulfur and the role…Question 336: Chromium is present in compound X. ● Two moles of compound X react with exactly 3 moles of silicon. ● The only products of this reaction ar…75 / 78
Question 337: In this question, the average oxidation state of sulfur in S2O3 2– and sulfur in S2O4 2– should be used. In which reaction does the underli…Question 338: When K2MnO4 reacts with concentrated hydrochloric acid, the products include chlorine molecules and MnCl 2. All of the manganese atoms are …Question 339: Sulfite ions, SO3 2–, react separately with zinc and with manganese dioxide. a, b, c, d, w, x, y and z are all whole numbers. aSO3 2–(aq) …Question 340: Which equation shows hydrogen acting as an oxidising agent? A H2 + 2K  2K+H– B H2 + I2 2HI C H2 + Cu2S + ZnO  2Cu + ZnS …76 / 78
Question 341: Photochromic glass, used for sunglasses, darkens when exposed to bright light and becomes more transparent again when the light is less bri…Question 342: What happens when iodine solution is added to a solution of sodium bromide? A A reaction occurs without changes in oxidation state. B Bromi…Question 343: The reaction of hydrogen sulfide with sulfur dioxide gives sulfur as one of the products. The two relevant redox equations are shown. H2S(a…Question 344: One commercially available ‘heat pad’ contains iron, activated carbon and water. The ‘heat pad’ is activated by air. This causes the pad to…77 / 78
Question 345: In which substance is the average oxidation number of sulfur the highest? A S8 B Na2S4O6 C Na2S2O3 D SO2Cl 2Question 346: In an experiment, 0.600 mol of chlorine gas, Cl 2, is reacted with an excess of hot aqueous sodium hydroxide. One of the products is NaCl O…Question 347: Sulfite ions, SO3 2–, react separately with zinc and with manganese dioxide. a, b, c, d, w, x, y and z are all whole numbers. aSO3 2–(aq) …Question 348: Which equation shows hydrogen acting as an oxidising agent? A H2 + 2K  2K+H– B H2 + I2 2HI C H2 + Cu2S + ZnO  2Cu + ZnS …Question 349: What happens when iodine solution is added to a solution of sodium bromide? A A reaction occurs without changes in oxidation state. B Bromi…78 / 78

Mark scheme349 answers

Answers below. Sit the paper first if you are practising.

Pastlit

Chemistry 9701 · Redox processes: electron transfer and changes in oxidation number (oxidation state) — Paper 1

A Level · topical answer key — answer key (teacher use)

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Answer

Marks

1B1
2B1
3C1
4C1
5B1
6B1
7B1
8A1
9A1
10B1
11A1
12C1
13C1
14D1
15A1
16D1
17D1
18A1
19D1
20B1
21C1
22B1
23D1
24A1
25B1
26D1
27C1
28B1
29D1
30A1
31D1
32B1
33C1
34B1
35D1
36D1
37B1
38A1
39B1
40C1
41B1
42B1
43D1
44D1
45A1
46A1
47B1
48D1
49D1
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Pastlit

Chemistry 9701 · Redox processes: electron transfer and changes in oxidation number (oxidation state) — Paper 1

A Level · topical answer key — answer key (teacher use)

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Marks

50A1
51A1
52A1
53A1
54B1
55C1
56A1
57B1
58—1
59—1
60—1
61—1
62C1
63C1
64A1
65B1
66D1
67A1
68C1
69C1
70B1
71C1
72D1
73C1
74C1
75A1
76D1
77C1
78C1
79B1
80B1
81A1
82D1
83B1
84B1
85A1
86D1
87A1
88D1
89D1
90A1
91B1
92B1
93C1
94D1
95B1
96D1
97A1
98B1
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Pastlit

Chemistry 9701 · Redox processes: electron transfer and changes in oxidation number (oxidation state) — Paper 1

A Level · topical answer key — answer key (teacher use)

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Answer

Marks

99B1
100C1
101D1
102D1
103A1
104A1
105B1
106C1
107C1
108B1
109B1
110A1
111B1
112C1
113C1
114B1
115B1
116D1
117B1
118B1
119D1
120A1
121C1
122D1
123A1
124C1
125B1
126D1
127B1
128B1
129D1
130D1
131A1
132D1
133A1
134C1
135D1
136A1
137B1
138A1
139C1
140C1
141B1
142—1
143—1
144—1
145A1
146A1
147D1
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Pastlit

Chemistry 9701 · Redox processes: electron transfer and changes in oxidation number (oxidation state) — Paper 1

A Level · topical answer key — answer key (teacher use)

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Answer

Marks

148A1
149C1
150C1
151C1
152A1
153A1
154A1
155D1
156A1
157B1
158D1
159A1
160B1
161C1
162C1
163C1
164B1
165A1
166B1
167D1
168A1
169C1
170A1
171D1
172A1
173D1
174D1
175B1
176A1
177A1
178D1
179B1
180D1
181B1
182D1
183A1
184A1
185B1
186D1
187D1
188D1
189D1
190A1
191B1
192C1
193B1
194C1
195D1
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Pastlit

Chemistry 9701 · Redox processes: electron transfer and changes in oxidation number (oxidation state) — Paper 1

A Level · topical answer key — answer key (teacher use)

Question

Answer

Marks

197C1
198B1
199B1
200C1
201D1
202B1
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Chemistry 9701 · Redox processes: electron transfer and changes in oxidation number (oxidation state) — Paper 1

A Level · topical answer key — answer key (teacher use)

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Chemistry 9701 · Redox processes: electron transfer and changes in oxidation number (oxidation state) — Paper 1

A Level · topical answer key — answer key (teacher use)

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Chemistry 9701 · Redox processes: electron transfer and changes in oxidation number (oxidation state) — Paper 1

A Level · topical answer key — answer key (teacher use)

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Another paper, or another topic

Paper
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Questions as text

Q1 · Chlorine dioxide is produced on a large scale as it is used for bleaching paper pulp 9701/11 Oct/Nov 2005

9 Chlorine dioxide is produced on a large scale as it is used for bleaching paper pulp. It is made by the following reaction. 2Cl O (aq) + SO2(g) → 2Cl O2(g) + SO − 2 4 (aq) − 3 How do the oxidation numbers of chlorine and sulphur change in this reaction? chlorine sulphur A decreases by 1 increases by 1 B decreases by 1 increases by 2 C decreases by 3 increases by 1 D decreases by 3 increases by 2

1 marks

Answer: B

This question in 9701/11 Oct/Nov 2005

Q2 · Chlorine reacts with hot concentrated aqueous sodium hydroxide according to the equation… 9701/11 Oct/Nov 2005

36 Chlorine reacts with hot concentrated aqueous sodium hydroxide according to the equation below. 3Cl2(g) + 6NaOH(aq) → NaCl O3(aq) + 5NaCl (aq) + 3H2O(l) Which conclusions can be drawn from this information? 1 The oxidation state of the chlorine in one of the products is +5. 2 The chlorine undergoes disproportionation. 3 The sodium hydroxide acts as a reducing agent.

1 marks

Answer: B

This question in 9701/11 Oct/Nov 2005

Q3 · The nickel-cadmium rechargeable battery is based upon the following overall reaction 9701/11 May/June 2006

9 The nickel-cadmium rechargeable battery is based upon the following overall reaction. Cd + 2NiOOH + 4H2O → Cd(OH)2 + 2Ni(OH)2.H2O What is the oxidation number of nickel at the beginning and at the end of the reaction? beginning end A +1.5 +2 B +2 +3 C +3 +2 D +3 +4

1 marks

Answer: C

This question in 9701/11 May/June 2006

Q4 · What happens when chlorine is bubbled through aqueous potassium iodide? 9701/11 May/June 2006

17 What happens when chlorine is bubbled through aqueous potassium iodide? A Chlorine is oxidised to chloride ions. B Hydrochloric acid is formed. C Iodide ions are oxidised to iodine. D Potassium iodide is reduced to iodine.

1 marks

Answer: C

This question in 9701/11 May/June 2006

Q5 · Aldehydes and ketones are carbonyl compounds 9701/11 May/June 2006

29 Aldehydes and ketones are carbonyl compounds. Which of them react both with NaBH4 and with Tollens’ reagent? A both aldehydes and ketones B aldehydes only C ketones only D neither aldehydes nor ketones

1 marks

Answer: B

This question in 9701/11 May/June 2006

Q6 · Ammonia and chlorine react in the gas phase 9701/11 May/June 2006

36 Ammonia and chlorine react in the gas phase. 8NH3 + 3Cl2 → N2 + 6NH4Cl Which statements are correct? 1 Ammonia behaves as a reducing agent. 2 Ammonia behaves as a base. 3 The oxidation number of the hydrogen changes.

1 marks

Answer: B

This question in 9701/11 May/June 2006

Q7 · In some early paintings, lead(II) carbonate was used as a white pigment 9701/11 Oct/Nov 2006

10 In some early paintings, lead(II) carbonate was used as a white pigment. In the 19th century hydrogen sulphide from burning coal reacted with this pigment to form black lead(II) sulphide, PbS. The original colour of the painting may be restored by carefully treating the area with dilute hydrogen peroxide, producing lead(II) sulphate which is also white. What is the role of the hydrogen peroxide? A catalyst B oxidising agent C reducing agent D solvent

1 marks

Answer: B

This question in 9701/11 Oct/Nov 2006

Q8 · What happens when chlorine is bubbled through aqueous sodium hydroxide solution? 9701/11 Oct/Nov 2006

35 What happens when chlorine is bubbled through aqueous sodium hydroxide solution? 1 In cold solution, ClO–(aq) ions are formed. 2 In hot solution, ClO3 –(aq) ions are formed. 3 Disproportionation of chlorine occurs in both cold and hot aqueous solutions.

1 marks

Answer: A

This question in 9701/11 Oct/Nov 2006

Q9 · The first stage in the manufacture of nitric acid is the oxidation of ammonia by oxygen 9701/11 Oct/Nov 2007

3 The first stage in the manufacture of nitric acid is the oxidation of ammonia by oxygen. wNH3(g) + xO2(g) → yNO(g) + zH2O(g) Which values for w, x, y and z are needed to balance the equation? w x y z A 4 5 4 6 B 4 6 4 5 C 5 6 5 4 D 6 5 6 4

1 marks

Answer: A

This question in 9701/11 Oct/Nov 2007

Q10 · In an experiment, 50.0 cm3 of a 0.10 mol dm–3 solution of a metallic salt reacted exactly… 9701/11 Oct/Nov 2007

9 In an experiment, 50.0 cm3 of a 0.10 mol dm–3 solution of a metallic salt reacted exactly with 25.0 cm3 of 0.10 mol dm–3 aqueous sodium sulphite. The half-equation for oxidation of sulphite ion is shown below. SO 3 (aq) + H2O(I) → SO 2 − 2 4 (aq) + 2H+(aq) + 2e– − If the original oxidation number of the metal in the salt was +3, what would be the new oxidation number of the metal? A +1 B +2 C +4 D +5

1 marks

Answer: B

This question in 9701/11 Oct/Nov 2007

Q11 · Carbon monoxide burns readily in oxygen to form carbon dioxide 9701/11 Oct/Nov 2007

32 Carbon monoxide burns readily in oxygen to form carbon dioxide. What can be deduced from this information? 1 The +4 oxidation state of carbon is more stable than the +2 state. 2 The standard enthalpy change of formation of carbon dioxide is more negative than that of carbon monoxide. 3 The value of the equilibrium constant for the reaction, 2CO(g) + O2(g) 2CO2(g), is likely to be high.

1 marks

Answer: A

This question in 9701/11 Oct/Nov 2007

Q12 · When the yellow liquid NCl3 is stirred into aqueous sodium hydroxide, the reaction that… 9701/11 May/June 2008

36 When the yellow liquid NCl3 is stirred into aqueous sodium hydroxide, the reaction that occurs can be represented by the following equation. 2NCl3(l) + 6NaOH(aq) → N2(g) + 3NaCl (aq) + 3NaOCl (aq) + 3H2O(l) What will be the result of this reaction? 1 The nitrogen is oxidised. 2 A bleaching solution remains after the reaction. 3 The final solution gives a precipitate with acidified silver nitrate.

1 marks

Answer: C

This question in 9701/11 May/June 2008

Q13 · In some fireworks there is a reaction between powdered aluminium and powdered barium… 9701/11 May/June 2009

11 In some fireworks there is a reaction between powdered aluminium and powdered barium nitrate in which heat is evolved and an unreactive gas is produced. What is the equation for this reaction? A 2Al + Ba(NO3)2 → Al2O3 + BaO + 2NO B 4Al + 4Ba(NO3)2 → 2Al2O3 + 4Ba(NO2)2 + O2 C 10Al + 3Ba(NO3)2 → 5Al2O3 + 3BaO + 3N2 D 10Al + 18Ba(NO3)2 → 10Al(NO3)3 + 18BaO + 3N2

1 marks

Answer: C

This question in 9701/11 May/June 2009

Q14 · Which conversion involves a reduction of chromium? 9701/11 Oct/Nov 2009

7 Which conversion involves a reduction of chromium? A CrO 2 − → CrO3 4 B CrO 2 − → Cr 2O 2 − 4 7 C CrO2Cl2 → CrO 2 − 4 D CrO2Cl2 → Cr2O3

1 marks

Answer: D

This question in 9701/11 Oct/Nov 2009

Q15 · Photochromic glass, used for sunglasses, darkens when exposed to bright light and becomes… 9701/11 Oct/Nov 2009

11 Photochromic glass, used for sunglasses, darkens when exposed to bright light and becomes more transparent again when the light is less bright. The depth of colour of the glass is related to the concentration of silver atoms. The following reactions are involved. reaction 1 Ag+ + Cl – Ag + Cl reaction 2 Cu+ + Cl → Cu2+ + Cl – reaction 3 Cu2+ + Ag → Cu+ + Ag+ Which statement about these reactions is correct? A Cu+ and Cu2+ ions act as catalysts. B Cu+ ions act as an oxidising agent in reaction 2. C Reaction 2 is the one in which light is absorbed. D Ag+ ions are oxidised in reaction 1.

1 marks

Answer: A

This question in 9701/11 Oct/Nov 2009

Q16 · Which statements about the reaction of solid sodium bromide with concentrated sulfuric… 9701/11 Oct/Nov 2009

36 Which statements about the reaction of solid sodium bromide with concentrated sulfuric acid are correct? 1 Hydrogen bromide is a product of the reaction. 2 Sulfuric acid is oxidised to sulfur dioxide. 3 Bromide ions are reduced to bromine.

1 marks

Answer: D

This question in 9701/11 Oct/Nov 2009

Q17 · Ammonium nitrate, NH4NO3, can decompose explosively when heated 9701/11 May/June 2010

6 Ammonium nitrate, NH4NO3, can decompose explosively when heated. NH4NO3 → N2O + 2H2O What are the changes in the oxidation numbers of the two nitrogen atoms in NH4NO3 when this reaction proceeds? A –2, –4 B +2, +6 C +4, –6 D +4, –4

1 marks

Answer: D

This question in 9701/11 May/June 2010

Q18 · How does concentrated sulfuric acid behave when it reacts with sodium chloride? 9701/11 May/June 2010

13 How does concentrated sulfuric acid behave when it reacts with sodium chloride? A as an acid only B as an acid and oxidising agent C as an oxidising agent only D as a reducing agent only

1 marks

Answer: A

This question in 9701/11 May/June 2010

Q19 · Which reactions are redox reactions? 9701/11 May/June 2010

32 Which reactions are redox reactions? 1 CaBr2 + 2H2SO4 → CaSO4 + Br2 + SO2 + 2H2O 2 CaBr2 + 2H3PO4 → Ca(H2PO4)2 + 2HBr 3 CaBr2 + 2AgNO3 → Ca(NO3)2 + 2AgBr

1 marks

Answer: D

This question in 9701/11 May/June 2010

Q20 · Sodium hydrogensulfide, NaSH, is used to remove hair from animal hides 9701/11 May/June 2010

33 Sodium hydrogensulfide, NaSH, is used to remove hair from animal hides. Which statements about the SH– ion are correct? 1 It contains 18 electrons. 2 Three lone pairs of electrons surround the sulfur atom. 3 Sulfur has an oxidation state of +2.

1 marks

Answer: B

This question in 9701/11 May/June 2010

Q21 · In a car engine, non-metallic element X forms a pollutant oxide Y 9701/11 May/June 2010

35 In a car engine, non-metallic element X forms a pollutant oxide Y. Further oxidation of Y to Z occurs in the atmosphere. In this further oxidation, 1 mol of Y reacts with ½ mol of gaseous oxygen. What can X be? 1 carbon 2 nitrogen 3 sulfur

1 marks

Answer: C

This question in 9701/11 May/June 2010

Q22 · Sulfur dioxide and sulfites are used in food preservation 9701/11 May/June 2010

36 Sulfur dioxide and sulfites are used in food preservation. Why are they used for this purpose? 1 They are reducing agents so retard the oxidation of food. 2 They inhibit the growth of aerobic bacteria. 3 They react with NO2(g) converting it to NO(g).

1 marks

Answer: B

This question in 9701/11 May/June 2010

Q23 · Ammonium nitrate, NH4NO3, can decompose explosively when heated 9701/12 May/June 2010

6 Ammonium nitrate, NH4NO3, can decompose explosively when heated. NH4NO3 → N2O + 2H2O What are the changes in the oxidation numbers of the two nitrogen atoms in NH4NO3 when this reaction proceeds? A –2, –4 B +2, +6 C +4, –6 D +4, –4

1 marks

Answer: D

This question in 9701/12 May/June 2010

Q24 · How does concentrated sulfuric acid behave when it reacts with sodium chloride? 9701/12 May/June 2010

14 How does concentrated sulfuric acid behave when it reacts with sodium chloride? A as an acid only B as an acid and oxidising agent C as an oxidising agent only D as a reducing agent only

1 marks

Answer: A

This question in 9701/12 May/June 2010

Q25 · Sodium hydrogensulfide, NaSH, is used to remove hair from animal hides 9701/12 May/June 2010

31 Sodium hydrogensulfide, NaSH, is used to remove hair from animal hides. Which statements about the SH– ion are correct? 1 It contains 18 electrons. 2 Three lone pairs of electrons surround the sulfur atom. 3 Sulfur has an oxidation state of +2.

1 marks

Answer: B

This question in 9701/12 May/June 2010

Q26 · Which reactions are redox reactions? 9701/12 May/June 2010

33 Which reactions are redox reactions? 1 CaBr2 + 2H2SO4 → CaSO4 + Br2 + SO2 + 2H2O 2 CaBr2 + 2H3PO4 → Ca(H2PO4)2 + 2HBr 3 CaBr2 + 2AgNO3 → Ca(NO3)2 + 2AgBr

1 marks

Answer: D

This question in 9701/12 May/June 2010

Q27 · In a car engine, non-metallic element X forms a pollutant oxide Y 9701/12 May/June 2010

35 In a car engine, non-metallic element X forms a pollutant oxide Y. Further oxidation of Y to Z occurs in the atmosphere. In this further oxidation, 1 mol of Y reacts with ½ mol of gaseous oxygen. What can X be? 1 carbon 2 nitrogen 3 sulfur

1 marks

Answer: C

This question in 9701/12 May/June 2010

Q28 · Sulfur dioxide and sulfites are used in food preservation 9701/12 May/June 2010

36 Sulfur dioxide and sulfites are used in food preservation. Why are they used for this purpose? 1 They are reducing agents so retard the oxidation of food. 2 They inhibit the growth of aerobic bacteria. 3 They react with NO2(g) converting it to NO(g).

1 marks

Answer: B

This question in 9701/12 May/June 2010

Q29 · Ammonium nitrate, NH4NO3, can decompose explosively when heated 9701/13 May/June 2010

7 Ammonium nitrate, NH4NO3, can decompose explosively when heated. NH4NO3 → N2O + 2H2O What are the changes in the oxidation numbers of the two nitrogen atoms in NH4NO3 when this reaction proceeds? A –2, –4 B +2, +6 C +4, –6 D +4, –4

1 marks

Answer: D

This question in 9701/13 May/June 2010

Q30 · How does concentrated sulfuric acid behave when it reacts with sodium chloride? 9701/13 May/June 2010

11 How does concentrated sulfuric acid behave when it reacts with sodium chloride? A as an acid only B as an acid and oxidising agent C as an oxidising agent only D as a reducing agent only

1 marks

Answer: A

This question in 9701/13 May/June 2010

Q31 · Which reactions are redox reactions? 9701/13 May/June 2010

31 Which reactions are redox reactions? 1 CaBr2 + 2H2SO4 → CaSO4 + Br2 + SO2 + 2H2O 2 CaBr2 + 2H3PO4 → Ca(H2PO4)2 + 2HBr 3 CaBr2 + 2AgNO3 → Ca(NO3)2 + 2AgBr

1 marks

Answer: D

This question in 9701/13 May/June 2010

Q32 · Sodium hydrogensulfide, NaSH, is used to remove hair from animal hides 9701/13 May/June 2010

32 Sodium hydrogensulfide, NaSH, is used to remove hair from animal hides. Which statements about the SH– ion are correct? 1 It contains 18 electrons. 2 Three lone pairs of electrons surround the sulfur atom. 3 Sulfur has an oxidation state of +2.

1 marks

Answer: B

This question in 9701/13 May/June 2010

Q33 · In a car engine, non-metallic element X forms a pollutant oxide Y 9701/13 May/June 2010

34 In a car engine, non-metallic element X forms a pollutant oxide Y. Further oxidation of Y to Z occurs in the atmosphere. In this further oxidation, 1 mol of Y reacts with ½ mol of gaseous oxygen. What can X be? 1 carbon 2 nitrogen 3 sulfur

1 marks

Answer: C

This question in 9701/13 May/June 2010

Q34 · Sulfur dioxide and sulfites are used in food preservation 9701/13 May/June 2010

36 Sulfur dioxide and sulfites are used in food preservation. Why are they used for this purpose? 1 They are reducing agents so retard the oxidation of food. 2 They inhibit the growth of aerobic bacteria. 3 They react with NO2(g) converting it to NO(g).

1 marks

Answer: B

This question in 9701/13 May/June 2010

Q35 · Sulfur dioxide, SO2, is added to wines to prevent oxidation of ethanol by air 9701/11 Oct/Nov 2010

4 Sulfur dioxide, SO2, is added to wines to prevent oxidation of ethanol by air. To determine the amount of SO2, a sample of wine is titrated with iodine, I2. In this reaction, one mole of SO2 is oxidised by one mole of I2. What is the change in oxidation number of sulfur in this reaction? A +2 to +4 B +2 to +6 C +4 to +5 D +4 to +6

1 marks

Answer: D

This question in 9701/11 Oct/Nov 2010

Q36 · Ammonium sulfate in nitrogenous fertilisers in the soil can be slowly oxidised by air… 9701/11 Oct/Nov 2010

15 Ammonium sulfate in nitrogenous fertilisers in the soil can be slowly oxidised by air producing sulfuric acid, nitric acid and water. How many moles of oxygen gas are needed to oxidise completely one mole of ammonium sulfate? A 1 B 2 C 3 D 4

1 marks

Answer: D

This question in 9701/11 Oct/Nov 2010

Q37 · Sulfur dioxide is used to bleach wood pulp in the production of paper 9701/11 Oct/Nov 2010

18 Sulfur dioxide is used to bleach wood pulp in the production of paper. It is also used as an additive in the production of jam and marmalade, often in the form of sulfite compounds. When it is present in quantities greater than 10 mg / kg it is required to be listed as an ingredient of the jam. Why is sulfur dioxide added to jam? A It is a bleaching agent and removes the undesirable colours from the fruit used in the jam. B It is a preservative that destroys unwanted bacteria and enzymes. C It is a reducing agent and removes the acids that give the jam a sharp taste. D It is an acidic gas and maintains the pH of the jam at a suitable value to give it a sharp taste.

1 marks

Answer: B

This question in 9701/11 Oct/Nov 2010

Q38 · Disproportionation is the term used to describe a reaction in which a reactant is… 9701/11 Oct/Nov 2010

35 Disproportionation is the term used to describe a reaction in which a reactant is simultaneously both oxidised and reduced. To which incomplete equations does the term disproportionation apply? 1 Cl2(g) + 2OH–(aq) → H2O(l) + Cl –(aq) + …… 2 3Cl2(g) + 6OH–(aq) → 3H2O(l) + ClO3 –(aq) + …… 3 2NO2(g) + H2O(l) → HNO3(aq) + ……

1 marks

Answer: A

This question in 9701/11 Oct/Nov 2010

Q39 · In aqueous solution, the acid HIO disproportionates according to the following equation… 9701/12 Oct/Nov 2010

13 In aqueous solution, the acid HIO disproportionates according to the following equation where m, n, p and q are simple whole numbers in their lowest ratios. mHIO → nI2 + pHIO3 + qH2O This equation can be balanced using oxidation numbers. What are the values for n and p? n p A 1 2 B 2 1 C 4 1 D 4 2

1 marks

Answer: B

This question in 9701/12 Oct/Nov 2010

Q40 · What happens when chlorine is bubbled through aqueous potassium iodide? 9701/12 Oct/Nov 2010

16 What happens when chlorine is bubbled through aqueous potassium iodide? A Chlorine is oxidised to chlorate(V) ions. B Chlorine is oxidised to chloride ions. C Iodide ions are oxidised to iodine. D There is no observable reaction.

1 marks

Answer: C

This question in 9701/12 Oct/Nov 2010

Q41 · Which pair of reagents will take part in a redox reaction? 9701/12 Oct/Nov 2010

26 Which pair of reagents will take part in a redox reaction? A CH3CH2OH + concentrated H2SO4 B CH3CHO + Tollens’ reagent C CH3CO2C2H5 + dilute H2SO4 D CH3COCH3 + Fehling’s solution

1 marks

Answer: B

This question in 9701/12 Oct/Nov 2010

Q42 · Zirconium, Zr, proton number 40, is a metal which is used in corrosion-resistant alloys 9701/12 Oct/Nov 2010

32 Zirconium, Zr, proton number 40, is a metal which is used in corrosion-resistant alloys. Zirconium metal is extracted from the oxide ZrO2 by the following sequence of reactions. reaction 1 ZrO2 + 2Cl 2 + 2C → ZrCl 4 + 2CO reaction 2 ZrCl 4 + 2Mg → Zr + 2MgCl 2 Which statements about this extraction process are correct? 1 Carbon in reaction 1 behaves as a reducing agent. 2 Magnesium in reaction 2 behaves as a reducing agent. 3 Chlorine in reaction 1 behaves as a reducing agent.

1 marks

Answer: B

This question in 9701/12 Oct/Nov 2010

Q43 · Sulfur dioxide, SO2, is added to wines to prevent oxidation of ethanol by air 9701/13 Oct/Nov 2010

4 Sulfur dioxide, SO2, is added to wines to prevent oxidation of ethanol by air. To determine the amount of SO2, a sample of wine is titrated with iodine, I2. In this reaction, one mole of SO2 is oxidised by one mole of I2. What is the change in oxidation number of sulfur in this reaction? A +2 to +4 B +2 to +6 C +4 to +5 D +4 to +6

1 marks

Answer: D

This question in 9701/13 Oct/Nov 2010

Q44 · Ammonium sulfate in nitrogenous fertilisers in the soil can be slowly oxidised by air… 9701/13 Oct/Nov 2010

15 Ammonium sulfate in nitrogenous fertilisers in the soil can be slowly oxidised by air producing sulfuric acid, nitric acid and water. How many moles of oxygen gas are needed to oxidise completely one mole of ammonium sulfate? A 1 B 2 C 3 D 4

1 marks

Answer: D

This question in 9701/13 Oct/Nov 2010

Q45 · Disproportionation is the term used to describe a reaction in which a reactant is… 9701/13 Oct/Nov 2010

34 Disproportionation is the term used to describe a reaction in which a reactant is simultaneously both oxidised and reduced. To which incomplete equations does the term disproportionation apply? 1 Cl2(g) + 2OH–(aq) → H2O(l) + Cl –(aq) + …… 2 3Cl2(g) + 6OH–(aq) → 3H2O(l) + ClO3 –(aq) + …… 3 2NO2(g) + H2O(l) → HNO3(aq) + ……

1 marks

Answer: A

This question in 9701/13 Oct/Nov 2010

Q46 · In flooded soils, like those used for rice cultivation, the oxygen content is low 9701/11 May/June 2011

2 In flooded soils, like those used for rice cultivation, the oxygen content is low. In such soils, anaerobic bacteria cause the loss of nitrogen from the soil as shown in the following sequence. In which step is the change in oxidation number (oxidation state) of nitrogen different to the changes in the other steps? A B C D NO3 –(aq) NO2 –(aq) NO(g) N2O(g) N2(g)

1 marks

Answer: A

This question in 9701/11 May/June 2011

Q47 · X, Y and Z represent different halogens 9701/11 May/June 2011

15 X, Y and Z represent different halogens. The table shows the results of nine experiments in which aqueous solutions of X2, Y2 and Z2 were separately added to separate aqueous solutions containing X –, Y – and Z – ions. X –(aq) Y –(aq) Z –(aq) X2(aq) no reaction no reaction no reaction Y2(aq) X2 formed no reaction Z2 formed Z2(aq) X2 formed no reaction no reaction Which row in the following table contains the ions X –, Y – and Z – in order of their decreasing strength as reducing agents? strongest weakest A X – Y – Z – B X – Z – Y – C Y – Z – X – D Z – X – Y –

1 marks

Answer: B

This question in 9701/11 May/June 2011

Q48 · A student observed the reactions when sodium chloride and sodium iodide were each reacted… 9701/11 May/June 2011

16 A student observed the reactions when sodium chloride and sodium iodide were each reacted separately with concentrated sulfuric acid and with concentrated phosphoric acid. The observations are recorded in the table. sodium chloride sodium iodide conc. H2SO4 colourless acidic gas formed purple vapour formed conc. H3PO4 colourless acidic gas formed colourless acidic gas formed Which deduction can be made from these observations? A Concentrated phosphoric acid is a stronger oxidising agent than concentrated sulfuric acid. B Concentrated phosphoric acid is a stronger oxidising agent than iodine. C Concentrated sulfuric acid is a stronger oxidising agent than chlorine. D Concentrated sulfuric acid is a stronger oxidising agent than iodine.

1 marks

Answer: D

This question in 9701/11 May/June 2011

Q49 · Concentrated sulfuric acid can behave both as a strong acid and as an oxidising agent 9701/12 May/June 2011

17 Concentrated sulfuric acid can behave both as a strong acid and as an oxidising agent. With which compound does concentrated sulfuric acid react in this way? A ethanol B magnesium carbonate C propanenitrile D sodium bromide

1 marks

Answer: D

This question in 9701/12 May/June 2011

Q50 · Which compound contains two different elements with identical oxidation states? 9701/12 May/June 2011

19 Which compound contains two different elements with identical oxidation states? A HCl O B Mg(OH)2 C Na2SO4 D NH4Cl

1 marks

Answer: A

This question in 9701/12 May/June 2011

Q51 · When the yellow liquid NCl 3 is stirred into aqueous sodium hydroxide, the reaction that… 9701/12 May/June 2011

35 When the yellow liquid NCl 3 is stirred into aqueous sodium hydroxide, the reaction that occurs can be represented by the following equation. 2NCl 3(l) + 6NaOH(aq) → N2(g) + 3NaCl (aq) + 3NaOCl (aq) + 3H2O(l) What will be the result of this reaction? 1 The nitrogen undergoes a redox reaction. 2 A bleaching solution remains after the reaction. 3 The final solution gives a precipitate with acidified silver nitrate.

1 marks

Answer: A

This question in 9701/12 May/June 2011

Q52 · In a car engine pollutant oxide Y, which contains non-metallic element X, is formed 9701/12 May/June 2011

36 In a car engine pollutant oxide Y, which contains non-metallic element X, is formed. Further oxidation of Y to Z occurs in the atmosphere. In this further oxidation, 1 mol of Y reacts with 0.5 mol of gaseous oxygen. X could be either nitrogen or sulfur. Which statements about X, Y and Z can be correct? 1 The oxidation number of X increases by two from Y to Z. 2 Y may have an unpaired electron in its molecule. 3 Y is a polar molecule.

1 marks

Answer: A

This question in 9701/12 May/June 2011

Q53 · In flooded soils, like those used for rice cultivation, the oxygen content is low 9701/13 May/June 2011

4 In flooded soils, like those used for rice cultivation, the oxygen content is low. In such soils, anaerobic bacteria cause the loss of nitrogen from the soil as shown in the following sequence. In which step is the change in oxidation number (oxidation state) of nitrogen different to the changes in the other steps? A B C D NO3 –(aq) NO2 –(aq) NO(g) N2O(g) N2(g)

1 marks

Answer: A

This question in 9701/13 May/June 2011

Q54 · X, Y and Z represent different halogens 9701/13 May/June 2011

16 X, Y and Z represent different halogens. The table shows the results of nine experiments in which aqueous solutions of X2, Y2 and Z2 were separately added to separate aqueous solutions containing X –, Y – and Z – ions. X –(aq) Y –(aq) Z –(aq) X2(aq) no reaction no reaction no reaction Y2(aq) X2 formed no reaction Z2 formed Z2(aq) X2 formed no reaction no reaction Which row in the following table contains the ions X –, Y – and Z – in order of their decreasing strength as reducing agents? strongest weakest A X – Y – Z – B X – Z – Y – C Y – Z – X – D Z – X – Y –

1 marks

Answer: B

This question in 9701/13 May/June 2011

Q55 · When chlorine and aqueous sodium hydroxide are heated together the following overall… 9701/11 Oct/Nov 2011

7 When chlorine and aqueous sodium hydroxide are heated together the following overall reaction occurs. 3Cl 2(aq) + 6NaOH(aq) → 5NaCl (aq) + NaCl O3(aq) + 3H2O(l) What are the oxidation numbers for chlorine in each of the following species? Cl 2 NaCl NaCl O3 A 0 +1 –5 B +2 –1 +3 C 0 –1 +5 D –2 +1 –3

1 marks

Answer: C

This question in 9701/11 Oct/Nov 2011

Q56 · Sulfur dioxide is used as a preservative in wine making 9701/11 Oct/Nov 2011

8 Sulfur dioxide is used as a preservative in wine making. The following equations describe how sulfur dioxide dissolves. H2O + SO2 HSO3 – + H+ HSO3 – + H+ SO3 2– + 2H+ Which statement about these two reactions is correct? A HSO3 – acts as a base. B SO2 acts as an oxidising agent. C SO3 2– acts as an acid. D SO3 2– acts as a reducing agent.

1 marks

Answer: A

This question in 9701/11 Oct/Nov 2011

Q57 · Which of the halide ions, chloride, bromide or iodide, acts as a reducing agent when its… 9701/11 Oct/Nov 2011

35 Which of the halide ions, chloride, bromide or iodide, acts as a reducing agent when its sodium salt reacts with concentrated sulfuric acid? 1 at least one of Cl –, Br – and I – 2 at least two of Cl –, Br – and I – 3 all three of Cl –, Br – and I –

1 marks

Answer: B

This question in 9701/11 Oct/Nov 2011

Q58 · Which pollutant, present in the exhaust fumes of an internal combustion engine, has an… 9701/12 Oct/Nov 2011

8 Which pollutant, present in the exhaust fumes of an internal combustion engine, has an element in the +2 oxidation state and an odd number of electrons in one molecule of the pollutant? A CO B H2S C NO D NO2

1 marks

This question in 9701/12 Oct/Nov 2011

Q59 · The amount of titanium dioxide in an ore can be determined by using the following reaction 9701/12 Oct/Nov 2011

11 The amount of titanium dioxide in an ore can be determined by using the following reaction. 3TiO2 + 4BrF3 → 3TiF4 + 2Br2 + 3O2 Which element increases in oxidation number in this reaction? A bromine B fluorine C oxygen D titanium

1 marks

This question in 9701/12 Oct/Nov 2011

Q60 · Sodium iodide reacts with concentrated sulfuric acid 9701/12 Oct/Nov 2011

16 Sodium iodide reacts with concentrated sulfuric acid. The equation which represents one of the reactions that takes place is shown. 8NaI + 9H2SO4 → 8NaHSO4 + 4I2 + H2S + 4H2O Which species has been oxidised in this reaction? A H+ B I– C Na+ D SO4 2–

1 marks

This question in 9701/12 Oct/Nov 2011

Q61 · In a car engine, non-metallic element X forms a pollutant oxide Y 9701/12 Oct/Nov 2011

36 In a car engine, non-metallic element X forms a pollutant oxide Y. Further oxidation of Y to Z occurs spontaneously in the atmosphere. In this further oxidation, 1 mol of Y reacts with 0.5 mol of gaseous oxygen. Which statements about X, Y and Z are correct? 1 The oxidation number of X increases by 2 from Y to Z. 2 The molecule of Y has no unpaired electrons. 3 The molecule of Z contains three oxygen atoms.

1 marks

This question in 9701/12 Oct/Nov 2011

Q62 · Use of the Data Booklet is relevant to this question 9701/13 Oct/Nov 2011

1 Use of the Data Booklet is relevant to this question. Lead(IV) chloride will oxidise bromide ions to bromine. The Pb4+ ions are reduced to Pb2+ ions in this reaction. If 6.980 g of lead(IV) chloride is added to an excess of sodium bromide solution, what mass of bromine would be produced? A 0.799 g B 1.598 g C 3.196 g D 6.392 g

1 marks

Answer: C

This question in 9701/13 Oct/Nov 2011

Q63 · When chlorine and aqueous sodium hydroxide are heated together the following overall… 9701/13 Oct/Nov 2011

6 When chlorine and aqueous sodium hydroxide are heated together the following overall reaction occurs. 3Cl 2(aq) + 6NaOH(aq) → 5NaCl (aq) + NaCl O3(aq) + 3H2O(l) What are the oxidation numbers for chlorine in each of the following species? Cl 2 NaCl NaCl O3 A 0 +1 –5 B +2 –1 +3 C 0 –1 +5 D –2 +1 –3

1 marks

Answer: C

This question in 9701/13 Oct/Nov 2011

Q64 · Sulfur dioxide is used as a preservative in wine making 9701/13 Oct/Nov 2011

10 Sulfur dioxide is used as a preservative in wine making. The following equations describe how sulfur dioxide dissolves. H2O + SO2 HSO3 – + H+ HSO3 – + H+ SO3 2– + 2H+ Which statement about these two reactions is correct? A HSO3 – acts as a base. B SO2 acts as an oxidising agent. C SO3 2– acts as an acid. D SO3 2– acts as a reducing agent.

1 marks

Answer: A

This question in 9701/13 Oct/Nov 2011

Q65 · Which of the halide ions, chloride, bromide or iodide, acts as a reducing agent when its… 9701/13 Oct/Nov 2011

33 Which of the halide ions, chloride, bromide or iodide, acts as a reducing agent when its sodium salt reacts with concentrated sulfuric acid? 1 at least one of Cl –, Br – and I – 2 at least two of Cl –, Br – and I – 3 all three of Cl –, Br – and I –

1 marks

Answer: B

This question in 9701/13 Oct/Nov 2011

Q66 · The oxide of titanium, TiO2, is used as a ‘whitener’ in toothpaste 9701/11 May/June 2012

10 The oxide of titanium, TiO2, is used as a ‘whitener’ in toothpaste. It is obtained from the ore iron(II) titanate, FeTiO3. What is the change, if any, in the oxidation number (oxidation state) of titanium in the reaction FeTiO3 → TiO2? A It is oxidised from +3 to +4. B It is reduced from +3 to +2. C It is reduced from +6 to +4. D There is no change in the oxidation number.

1 marks

Answer: D

This question in 9701/11 May/June 2012

Q67 · The diagram shows a cell for the manufacture of aluminium 9701/11 May/June 2012

11 The diagram shows a cell for the manufacture of aluminium. graphite anodes mixture of Al 2O3 and molten cryolite graphite lining acting as cathode molten aluminium Which statement is incorrect? A Aluminium ions are oxidised in this process. B Aluminium is liberated at the cathode by the reaction Al 3+ + 3e– → Al . C The cryolite acts as a solvent. D The graphite anode burns away.

1 marks

Answer: A

This question in 9701/11 May/June 2012

Q68 · In the treatment of domestic water supplies, chlorine is added to the water to form HCl O 9701/11 May/June 2012

16 In the treatment of domestic water supplies, chlorine is added to the water to form HCl O. Cl 2(aq) + H2O(I) → H+(aq) + Cl –(aq) + HCl O(aq) The HCl O reacts further to give Cl O– ions. HCl O(aq) + H2O(I) → H3O+(aq) + Cl O–(aq) Both HCl O and Cl O– kill bacteria by oxidation. What is the overall change in oxidation number of chlorine when forming the Cl O– ion from the aqueous chlorine? A –1 B 0 C +1 D +2

1 marks

Answer: C

This question in 9701/11 May/June 2012

Q69 · Carbon monoxide, CO, nitrogen monoxide, NO, and sulfur dioxide, SO2, may all be present… 9701/11 May/June 2012

19 Carbon monoxide, CO, nitrogen monoxide, NO, and sulfur dioxide, SO2, may all be present in the exhaust fumes from a car engine. Which reaction concerning these compounds occurs in the atmosphere? A CO is spontaneously oxidised to CO2 B NO2 is reduced to NO by CO C NO2 is reduced to NO by SO2 D SO2 is oxidised to SO3 by CO2

1 marks

Answer: C

This question in 9701/11 May/June 2012

Q70 · Ammonia and chlorine react in the gas phase 9701/11 May/June 2012

34 Ammonia and chlorine react in the gas phase. 8NH3 + 3Cl 2 → N2 + 6NH4Cl Which statements are correct? 1 Ammonia behaves as a reducing agent. 2 Ammonia behaves as a base. 3 The oxidation number of the hydrogen changes

1 marks

Answer: B

This question in 9701/11 May/June 2012

Q71 · In which substance does nitrogen exhibit the highest oxidation state? 9701/12 May/June 2012

11 In which substance does nitrogen exhibit the highest oxidation state? A NO B N2O C N2O4 D NaNO2

1 marks

Answer: C

This question in 9701/12 May/June 2012

Q72 · Chlorine shows oxidation states ranging from –1 to +7 in its compounds 9701/12 May/June 2012

16 Chlorine shows oxidation states ranging from –1 to +7 in its compounds. What are the reagent(s) and conditions necessary for the oxidation of elemental chlorine into a compound containing chlorine in the +5 oxidation state? A AgNO3(aq) followed by NH3(aq) at room temperature B concentrated H2SO4 at room temperature C cold dilute NaOH(aq) D hot concentrated NaOH(aq)

1 marks

Answer: D

This question in 9701/12 May/June 2012

Q73 · Ammonia and chlorine react in the gas phase 9701/12 May/June 2012

32 Ammonia and chlorine react in the gas phase. 8NH3 + 3Cl 2 → N2 + 6NH4Cl Which statements are correct? 1 Each nitrogen atom is oxidised. 2 Each chlorine atom is reduced. 3 Ammonia behaves as a base.

1 marks

Answer: C

This question in 9701/12 May/June 2012

Q74 · Two conversions are outlined below 9701/13 May/June 2012

6 Two conversions are outlined below. NH4 + → NH3 C2H4 → C2H6 What similar feature do these two conversions have? A a lone pair of electrons in the product B change in oxidation state of an element C decrease in bond angle of the species involved D disappearance of a π bond

1 marks

Answer: C

This question in 9701/13 May/June 2012

Q75 · The diagram shows a cell for the manufacture of aluminium 9701/13 May/June 2012

9 The diagram shows a cell for the manufacture of aluminium. graphite anodes mixture of Al 2O3 and molten cryolite graphite lining acting as cathode molten aluminium Which statement is incorrect? A Aluminium ions are oxidised in this process. B Aluminium is liberated at the cathode by the reaction Al 3+ + 3e– → Al . C The cryolite acts as a solvent. D The graphite anode burns away.

1 marks

Answer: A

This question in 9701/13 May/June 2012

Q76 · The oxide of titanium, TiO2, is used as a ‘whitener’ in toothpaste 9701/13 May/June 2012

10 The oxide of titanium, TiO2, is used as a ‘whitener’ in toothpaste. It is obtained from the ore iron(II) titanate, FeTiO3. What is the change, if any, in the oxidation number (oxidation state) of titanium in the reaction FeTiO3 → TiO2? A It is oxidised from +3 to +4. B It is reduced from +3 to +2. C It is reduced from +6 to +4. D There is no change in the oxidation number.

1 marks

Answer: D

This question in 9701/13 May/June 2012

Q77 · In the treatment of domestic water supplies, chlorine is added to the water to form HCl O 9701/13 May/June 2012

17 In the treatment of domestic water supplies, chlorine is added to the water to form HCl O. Cl 2(aq) + H2O(I) → H+(aq) + Cl –(aq) + HCl O(aq) The HCl O reacts further to give Cl O– ions. HCl O(aq) + H2O(I) → H3O+(aq) + Cl O–(aq) Both HCl O and Cl O– kill bacteria by oxidation. What is the overall change in oxidation number of chlorine when forming the Cl O– ion from the aqueous chlorine? A –1 B 0 C +1 D +2

1 marks

Answer: C

This question in 9701/13 May/June 2012

Q78 · Carbon monoxide, CO, nitrogen monoxide, NO, and sulfur dioxide, SO2, may all be present… 9701/13 May/June 2012

20 Carbon monoxide, CO, nitrogen monoxide, NO, and sulfur dioxide, SO2, may all be present in the exhaust fumes from a car engine. Which reaction concerning these compounds occurs in the atmosphere? A CO is spontaneously oxidised to CO2 B NO2 is reduced to NO by CO C NO2 is reduced to NO by SO2 D SO2 is oxidised to SO3 by CO2

1 marks

Answer: C

This question in 9701/13 May/June 2012

Q79 · Ammonia and chlorine react in the gas phase 9701/13 May/June 2012

36 Ammonia and chlorine react in the gas phase. 8NH3 + 3Cl 2 → N2 + 6NH4Cl Which statements are correct? 1 Ammonia behaves as a reducing agent. 2 Ammonia behaves as a base. 3 The oxidation number of the hydrogen changes.

1 marks

Answer: B

This question in 9701/13 May/June 2012

Q80 · In which reaction does an element undergo the largest change in oxidation state? 9701/11 Oct/Nov 2012

1 In which reaction does an element undergo the largest change in oxidation state? A Cl 2 + 2OH– → OCl – + Cl – + H2O B 3Cl 2 + 6OH– → Cl O3 – + 5Cl – + 3H2O C Cr2O7 2– + 6Fe2+ + 14H+ → 2Cr3+ + 6Fe3+ + 7H2O D 3MnO4 2– + 4H+ → MnO2 + 2MnO4 – + 2H2O

1 marks

Answer: B

This question in 9701/11 Oct/Nov 2012

Q81 · In a car engine, non-metallic element X forms a pollutant oxide Y 9701/11 Oct/Nov 2012

16 In a car engine, non-metallic element X forms a pollutant oxide Y. Y can be further oxidised to Z. Two students made the following statements. Student P The molecule of Y contains lone pairs of electrons. Student Q The oxidation number of X increases by 1 from Y to Z. X could be carbon or nitrogen or sulfur. Which student could be correct if X were any of these elements? A P only B Q only C both P and Q D neither P nor Q

1 marks

Answer: A

This question in 9701/11 Oct/Nov 2012

Q82 · One of the reactions taking place in a catalytic converter in a car exhaust system is… 9701/11 Oct/Nov 2012

25 One of the reactions taking place in a catalytic converter in a car exhaust system is between nitrogen oxide and octane (unburned petrol). The products of this reaction are non-toxic. Which is the correct equation for the reaction? A C8H16 + 16NO → 8CO + 8N2 + 8H2O B C8H16 + 24NO → 8CO2 + 12N2 + 8H2O C C8H18 + 17NO → 8CO + 8 2 1 N2 + 9H2O D C8H18 + 25NO → 8CO2 + 12 2 1 N2 + 9H2O

1 marks

Answer: D

This question in 9701/11 Oct/Nov 2012

Q83 · How may nitrogen exist in compounds? 9701/11 Oct/Nov 2012

31 How may nitrogen exist in compounds? 1 bonded by a triple covalent bond 2 as part of a cation 3 having lost 3 electrons to form an anion

1 marks

Answer: B

This question in 9701/11 Oct/Nov 2012

Q84 · In which reaction does an element undergo the largest change in oxidation state? 9701/12 Oct/Nov 2012

1 In which reaction does an element undergo the largest change in oxidation state? A Cl 2 + 2OH– → OCl – + Cl – + H2O B 3Cl 2 + 6OH– → Cl O3 – + 5Cl – + 3H2O C Cr2O7 2– + 6Fe2+ + 14H+ → 2Cr3+ + 6Fe3+ + 7H2O D 3MnO4 2– + 4H+ → MnO2 + 2MnO4 – + 2H2O

1 marks

Answer: B

This question in 9701/12 Oct/Nov 2012

Q85 · In a car engine, non-metallic element X forms a pollutant oxide Y 9701/12 Oct/Nov 2012

16 In a car engine, non-metallic element X forms a pollutant oxide Y. Y can be further oxidised to Z. Two students made the following statements. Student P The molecule of Y contains lone pairs of electrons. Student Q The oxidation number of X increases by 1 from Y to Z. X could be carbon or nitrogen or sulfur. Which student could be correct if X were any of these elements? A P only B Q only C both P and Q D neither P nor Q

1 marks

Answer: A

This question in 9701/12 Oct/Nov 2012

Q86 · One of the reactions taking place in a catalytic converter in a car exhaust system is… 9701/12 Oct/Nov 2012

25 One of the reactions taking place in a catalytic converter in a car exhaust system is between nitrogen oxide and octane (unburned petrol). The products of this reaction are non-toxic. Which is the correct equation for the reaction? A C8H16 + 16NO → 8CO + 8N2 + 8H2O B C8H16 + 24NO → 8CO2 + 12N2 + 8H2O C C8H18 + 17NO → 8CO + 8 2 1 N2 + 9H2O D C8H18 + 25NO → 8CO2 + 12 2 1 N2 + 9H2O

1 marks

Answer: D

This question in 9701/12 Oct/Nov 2012

Q87 · Aluminium is extracted by the electrolysis of a molten mixture containing aluminium oxide 9701/13 Oct/Nov 2012

4 Aluminium is extracted by the electrolysis of a molten mixture containing aluminium oxide. By a similar method, magnesium is extracted by the electrolysis of a molten mixture containing magnesium chloride. Which statement about this electrolysis is correct? A Chloride ions travel to the anode and are oxidised to chlorine gas. B Chloride ions travel to the anode and are reduced to chlorine gas. C Chloride ions travel to the cathode and are oxidised to chlorine gas. D Chloride ions travel to the cathode and are reduced to chlorine gas.

1 marks

Answer: A

This question in 9701/13 Oct/Nov 2012

Q88 · The reaction between KI and concentrated H2SO4 is a redox reaction 9701/13 Oct/Nov 2012

15 The reaction between KI and concentrated H2SO4 is a redox reaction. 5H2SO4 + 8KI → 4K2SO4 + 4I2 + H2S + 4H2O What is the change in oxidation state of the element that is reduced? A 1 B 4 C 6 D 8

1 marks

Answer: D

This question in 9701/13 Oct/Nov 2012

Q89 · Deposits of ammonium sulfate have been discovered in areas of high atmospheric pollution 9701/13 Oct/Nov 2012

19 Deposits of ammonium sulfate have been discovered in areas of high atmospheric pollution. They are believed to arise from the following reaction. SO3 + H2O + 2NH3 → (NH4)2SO4 What does not occur in this reaction? A acid / base neutralisation B dative bond formation C ionic bond formation D oxidation / reduction

1 marks

Answer: D

This question in 9701/13 Oct/Nov 2012

Q90 · How may nitrogen exist in compounds? 9701/13 Oct/Nov 2012

31 How may nitrogen exist in compounds? 1 bonded by a triple covalent bond 2 as part of a cation 3 in an oxidation state of +5

1 marks

Answer: A

This question in 9701/13 Oct/Nov 2012

Q91 · An element X and compound YZ react separately with acid as shown 9701/13 Oct/Nov 2012

34 An element X and compound YZ react separately with acid as shown. X(s) + 2H+(aq) → X2+(aq) + H2(g) YZ(s) + 2H+(aq) → Y2+(aq) + H2Z(g) When 1.0 g of either X or YZ is reacted with an excess of acid, the total volume of gas formed is the same. Which statements are correct? 1 Ar(X) = Mr(YZ) 2 X and Y are metals. 3 X and Y must both be in the same Group of the Periodic Table.

1 marks

Answer: B

This question in 9701/13 Oct/Nov 2012

Q92 · Which pairs of reagents will react together in a redox reaction? 9701/13 Oct/Nov 2012

38 Which pairs of reagents will react together in a redox reaction? 1 CH3CHO + Fehling’s reagent 2 CH4 + Cl 2 3 CH3COCH3 + Tollens’ reagent

1 marks

Answer: B

This question in 9701/13 Oct/Nov 2012

Q93 · Solutions containing chlorate(I) ions are used as household bleaches and disinfectants 9701/11 May/June 2013

1 Solutions containing chlorate(I) ions are used as household bleaches and disinfectants. These solutions decompose on heating as shown. 3Cl O– → Cl O3 – + 2Cl – Which oxidation state is shown by chlorine in each of these three ions? Cl O– Cl O3 – Cl – A +1 +3 –1 B –1 +3 +1 C +1 +5 –1 D –1 +5 +1

1 marks

Answer: C

This question in 9701/11 May/June 2013

Q94 · The diagram shows an electrolytic cell for the extraction of aluminium 9701/11 May/June 2013

3 The diagram shows an electrolytic cell for the extraction of aluminium. graphite anode Al 2O3 in molten cryolite graphite lining acting as cathode molten aluminium Which statement is correct? A Aluminium ions are oxidised in this process. B Aluminium is liberated at the anode by the reaction Al 3+ + 3e– → Al. C Cryolite is purified aluminium oxide. D The graphite anode burns away.

1 marks

Answer: D

This question in 9701/11 May/June 2013

Q95 · A solution of Sn2+ ions will reduce an acidified solution of MnO4 – ions to Mn2+ ions 9701/11 May/June 2013

11 A solution of Sn2+ ions will reduce an acidified solution of MnO4 – ions to Mn2+ ions. The Sn2+ ions are oxidised to Sn4+ ions in this reaction. How many moles of Mn2+ ions are formed when a solution containing 9.5 g of SnCl 2 (Mr: 190) is added to an excess of acidified KMnO4 solution? A 0.010 B 0.020 C 0.050 D 0.125

1 marks

Answer: B

This question in 9701/11 May/June 2013

Q96 · What happens when iodine solution is added to a solution of sodium bromide? 9701/11 May/June 2013

14 What happens when iodine solution is added to a solution of sodium bromide? A A reaction occurs without changes in oxidation state. B Bromide ions are oxidised, iodine atoms are reduced. C Bromide ions are reduced, iodine atoms are oxidised. D No reaction occurs.

1 marks

Answer: D

This question in 9701/11 May/June 2013

Q97 · Element 85, astatine, is in Group VII 9701/11 May/June 2013

15 Element 85, astatine, is in Group VII. Concentrated sulfuric acid is added to sodium astatide. The mixture of products includes astatine, hydrogen astatide, hydrogen sulfide, and sodium sulfate. Which product is formed by the oxidation of one of the constituents of sodium astatide? A astatine B hydrogen astatide C hydrogen sulfide D sodium sulfate

1 marks

Answer: A

This question in 9701/11 May/June 2013

Q98 · In which reactions is the organic compound oxidised by the given reagent? 9701/11 May/June 2013

38 In which reactions is the organic compound oxidised by the given reagent? 1 CH3CH2CHO + Fehling’s reagent 2 CH3CH2CH2CHO + Tollens’ reagent 3 CH3CHO + 2,4-dinitrophenylhydrazine reagent

1 marks

Answer: B

This question in 9701/11 May/June 2013

Q99 · During the electrolysis of molten aluminium oxide to produce aluminium, using carbon… 9701/12 May/June 2013

1 During the electrolysis of molten aluminium oxide to produce aluminium, using carbon electrodes, two consecutive reactions occur at the anode, each producing a different gas. How does the oxidation number of oxygen change in these reactions? A decreases by 2, then increases by 2 B increases by 2, then decreases by 2 C increases by 2, then decreases by 4 D no change, then decreases by 2

1 marks

Answer: B

This question in 9701/12 May/June 2013

Q100 · What happens when bromine solution is added to a solution of sodium iodide? 9701/12 May/June 2013

18 What happens when bromine solution is added to a solution of sodium iodide? A A reaction occurs without changes in oxidation state. B Bromine atoms are oxidised, iodide ions are reduced. C Bromine atoms are reduced, iodide ions are oxidised. D No reaction occurs.

1 marks

Answer: C

This question in 9701/12 May/June 2013

Q101 · Sulfur dioxide is an atmospheric pollutant that causes acid rain 9701/12 May/June 2013

36 Sulfur dioxide is an atmospheric pollutant that causes acid rain. One of the reactions in this process is the oxidation of sulfur dioxide to sulfur trioxide. This oxidation takes place by a two stage reaction involving oxygen and nitrogen monoxide, NO. NO + 2 1 O2 → NO2 NO2 + SO2 → SO3 + NO Which statements are correct? 1 Nitrogen monoxide is acting as a catalyst for the oxidation. 2 Nitrogen atoms are oxidised in the second stage. 3 Oxygen atoms are first reduced and are then oxidised.

1 marks

Answer: D

This question in 9701/12 May/June 2013

Q102 · In the redox reaction shown, how do the oxidation states of vanadium and sulfur change? 9701/13 May/June 2013

1 In the redox reaction shown, how do the oxidation states of vanadium and sulfur change? VO2 + + SO2 → V3+ + SO4 2– vanadium sulfur from to from to A +1 +3 0 –2 B +1 +3 +4 +6 C +5 +3 0 –2 D +5 +3 +4 +6

1 marks

Answer: D

This question in 9701/13 May/June 2013

Q103 · A space shuttle’s upward thrust came from the following reaction between aluminium and… 9701/13 May/June 2013

31 A space shuttle’s upward thrust came from the following reaction between aluminium and ammonium perchlorate. 10Al + 6NH4Cl O4 → 4Al 2O3 + 2Al Cl 3 + 12H2O + 3N2 Which statements about this reaction are correct? 1 Aluminium is oxidised. 2 Chlorine is reduced. 3 Nitrogen is oxidised.

1 marks

Answer: A

This question in 9701/13 May/June 2013

Q104 · In which reaction does a single nitrogen atom have the greatest change in oxidation… 9701/11 Oct/Nov 2013

2 In which reaction does a single nitrogen atom have the greatest change in oxidation number? A 4NH3 + 5O2 → 4NO + 6H2O B 3NO2 + H2O → 2HNO3 + NO C 2NO + O2 → 2NO2 D 4NH3 + 6NO → 5N2 + 6H2O

1 marks

Answer: A

This question in 9701/11 Oct/Nov 2013

Q105 · The following half reactions occur when potassium iodate(V), KIO3, in hydrochloric acid… 9701/11 Oct/Nov 2013

3 The following half reactions occur when potassium iodate(V), KIO3, in hydrochloric acid solution oxidises iodine to ICl 2 –. IO3 – + 2Cl – + 6H+ + 4e– → ICl 2 – + 3H2O I2 + 4Cl – → 2ICl 2 – + 2e– What is the ratio of IO3 – to I2 in the balanced chemical equation for the overall reaction? A 1 : 1 B 1 : 2 C 1 : 4 D 2 : 1

1 marks

Answer: B

This question in 9701/11 Oct/Nov 2013

Q106 · Solid potassium halides react with concentrated sulfuric acid, according to the following… 9701/11 Oct/Nov 2013

16 Solid potassium halides react with concentrated sulfuric acid, according to the following equations. reaction 1 2KCl + H2SO4 → K2SO4 + 2HCl reaction 2 2KBr + 2H2SO4 → K2SO4 + SO2 + Br2 + 2H2O reaction 3 8KI + 5H2SO4 → 4K2SO4 + H2S + 4I2 + 4H2O What is the largest change in the oxidation number of sulfur in each of these reactions? reaction 1 reaction 2 reaction 3 A 0 0 4 B 0 2 4 C 0 2 8 D 0 4 8

1 marks

Answer: C

This question in 9701/11 Oct/Nov 2013

Q107 · Primary alcohols can be oxidised to aldehydes using either acidified potassium… 9701/11 Oct/Nov 2013

27 Primary alcohols can be oxidised to aldehydes using either acidified potassium dichromate(VI) or acidified potassium manganate(VII). Both these oxidising agents change colour as they are reduced. What is the colour of each oxidising agent before and after it has reacted? acidified potassium dichromate(VI) acidified potassium manganate(VII) before after before after A green orange purple colourless B orange green colourless purple C orange green purple colourless D purple colourless orange green

1 marks

Answer: C

This question in 9701/11 Oct/Nov 2013

Q108 · In which reaction is the organic compound oxidised? 9701/11 Oct/Nov 2013

28 In which reaction is the organic compound oxidised? A CH3CH2OH + concentrated H3PO4 B CH3CH2CH2CHO + Tollens’ reagent C CH3COCH3 + 2,4-dinitrophenylhydrazine reagent D CH3CN + dilute H2SO4

1 marks

Answer: B

This question in 9701/11 Oct/Nov 2013

Q109 · Sulfur dioxide and sulfites are used in food preservation 9701/11 Oct/Nov 2013

36 Sulfur dioxide and sulfites are used in food preservation. Why are they used for this purpose? 1 They are reducing agents which slow down the oxidation of food. 2 They inhibit the growth of aerobic bacteria. 3 They react with NO2(g) converting it to NO(g).

1 marks

Answer: B

This question in 9701/11 Oct/Nov 2013

Q110 · In which reaction does a single nitrogen atom have the greatest change in oxidation… 9701/12 Oct/Nov 2013

2 In which reaction does a single nitrogen atom have the greatest change in oxidation number? A 4NH3 + 5O2 → 4NO + 6H2O B 3NO2 + H2O → 2HNO3 + NO C 2NO + O2 → 2NO2 D 4NH3 + 6NO → 5N2 + 6H2O

1 marks

Answer: A

This question in 9701/12 Oct/Nov 2013

Q111 · The following half reactions occur when potassium iodate(V), KIO3, in hydrochloric acid… 9701/12 Oct/Nov 2013

3 The following half reactions occur when potassium iodate(V), KIO3, in hydrochloric acid solution oxidises iodine to ICl 2 –. IO3 – + 2Cl – + 6H+ + 4e– → ICl 2 – + 3H2O I2 + 4Cl – → 2ICl 2 – + 2e– What is the ratio of IO3 – to I2 in the balanced chemical equation for the overall reaction? A 1 : 1 B 1 : 2 C 1 : 4 D 2 : 1

1 marks

Answer: B

This question in 9701/12 Oct/Nov 2013

Q112 · Solid potassium halides react with concentrated sulfuric acid, according to the following… 9701/12 Oct/Nov 2013

16 Solid potassium halides react with concentrated sulfuric acid, according to the following equations. reaction 1 2KCl + H2SO4 → K2SO4 + 2HCl reaction 2 2KBr + 2H2SO4 → K2SO4 + SO2 + Br2 + 2H2O reaction 3 8KI + 5H2SO4 → 4K2SO4 + H2S + 4I2 + 4H2O What is the largest change in the oxidation number of sulfur in each of these reactions? reaction 1 reaction 2 reaction 3 A 0 0 4 B 0 2 4 C 0 2 8 D 0 4 8

1 marks

Answer: C

This question in 9701/12 Oct/Nov 2013

Q113 · Primary alcohols can be oxidised to aldehydes using either acidified potassium… 9701/12 Oct/Nov 2013

27 Primary alcohols can be oxidised to aldehydes using either acidified potassium dichromate(VI) or acidified potassium manganate(VII). Both these oxidising agents change colour as they are reduced. What is the colour of each oxidising agent before and after it has reacted? acidified potassium dichromate(VI) acidified potassium manganate(VII) before after before after A green orange purple colourless B orange green colourless purple C orange green purple colourless D purple colourless orange green

1 marks

Answer: C

This question in 9701/12 Oct/Nov 2013

Q114 · In which reaction is the organic compound oxidised? 9701/12 Oct/Nov 2013

28 In which reaction is the organic compound oxidised? A CH3CH2OH + concentrated H3PO4 B CH3CH2CH2CHO + Tollens’ reagent C CH3COCH3 + 2,4-dinitrophenylhydrazine reagent D CH3CN + dilute H2SO4

1 marks

Answer: B

This question in 9701/12 Oct/Nov 2013

Q115 · Sulfur dioxide and sulfites are used in food preservation 9701/12 Oct/Nov 2013

36 Sulfur dioxide and sulfites are used in food preservation. Why are they used for this purpose? 1 They are reducing agents which slow down the oxidation of food. 2 They inhibit the growth of aerobic bacteria. 3 They react with NO2(g) converting it to NO(g).

1 marks

Answer: B

This question in 9701/12 Oct/Nov 2013

Q116 · Ammonium nitrate, NH4NO3, can decompose explosively when heated 9701/13 Oct/Nov 2013

1 Ammonium nitrate, NH4NO3, can decompose explosively when heated. NH4NO3 → N2O + 2H2O What are the changes in the oxidation numbers of the two nitrogen atoms in NH4NO3 when this reaction proceeds? A –2, –4 B +2, +6 C +4, –6 D +4, –4

1 marks

Answer: D

This question in 9701/13 Oct/Nov 2013

Q117 · A 10 cm3 sample of 0.30 mol dm–3 Tl +NO3 – required 20 cm3 of 0.10 mol dm–3 acidified… 9701/13 Oct/Nov 2013

3 A 10 cm3 sample of 0.30 mol dm–3 Tl +NO3 – required 20 cm3 of 0.10 mol dm–3 acidified NH4VO3 to oxidise it to Tl 3+ in solution. Vanadium is the only element reduced in this reaction. What is the oxidation number of the vanadium in the reduced form? A +1 B +2 C +3 D +4

1 marks

Answer: B

This question in 9701/13 Oct/Nov 2013

Q118 · The Contact process is used in the manufacture of sulfuric acid 9701/11 May/June 2014

7 The Contact process is used in the manufacture of sulfuric acid. The equation for the main reaction is shown below. 2SO2(g) + O2(g) 2SO3(g) ∆H = –196 kJ mol–1 Which statement about this reaction is incorrect? A Increased pressure gives a higher yield of SO3. B Increased temperature gives a higher yield of SO3. C In the forward reaction the oxidation state of sulfur changes from +4 to +6. D Vanadium(V) oxide is used as a catalyst.

1 marks

Answer: B

This question in 9701/11 May/June 2014

Q119 · Redox reactions occur very frequently in the chemistry of Group VII 9701/11 May/June 2014

12 Redox reactions occur very frequently in the chemistry of Group VII. Which statement is correct? A Chlorine will oxidise bromide ions but not iodide ions. B Fluorine is the weakest oxidising agent out of F2, Cl 2, Br2 and I2. C Iodide ions are the weakest reducing agent out of F –, Cl –, Br – and I –. D When chlorine reacts with water, chlorine is both oxidised and reduced.

1 marks

Answer: D

This question in 9701/11 May/June 2014

Q120 · Pollutant oxide Y, which contains non-metallic element X, is formed in a car engine 9701/11 May/June 2014

35 Pollutant oxide Y, which contains non-metallic element X, is formed in a car engine. Further oxidation of Y to Z occurs in the atmosphere. In this further oxidation, 1 mol of Y reacts with 0.5 mol of gaseous oxygen molecules. X could be either nitrogen or sulfur. Which statements about X, Y and Z can be correct? 1 The oxidation number of X increases by two from Y to Z. 2 Y has an unpaired electron in its molecule. 3 Y is a polar molecule.

1 marks

Answer: A

This question in 9701/11 May/June 2014

Q121 · In which reaction is the species in bold acting as an oxidising agent? 9701/12 May/June 2014

6 In which reaction is the species in bold acting as an oxidising agent? A 2Ca + O2 → 2CaO B Cr2O7 2– + 8H+ + 3SO3 2– → 2Cr3+ + 4H2O + 3SO4 2– C Mg + Fe2+ → Mg2+ + Fe D SO2 + 2H2O + 2Cu2+ + 2Cl – → H2SO4 + 2H+ + 2CuCl

1 marks

Answer: C

This question in 9701/12 May/June 2014

Q122 · Ammonium sulfate in the soil is slowly oxidised by air, producing sulfuric acid, nitric… 9701/12 May/June 2014

14 Ammonium sulfate in the soil is slowly oxidised by air, producing sulfuric acid, nitric acid and water as the only products. How many moles of oxygen gas are needed for the complete oxidation of one mole of ammonium sulfate? A 1 B 2 C 3 D 4

1 marks

Answer: D

This question in 9701/12 May/June 2014

Q123 · When solid sodium iodide reacts with concentrated sulfuric acid, the products include… 9701/12 May/June 2014

17 When solid sodium iodide reacts with concentrated sulfuric acid, the products include NaHSO4, H2S, SO2 and S. In the formation of which product has the oxidation state of sulfur changed by a value of 8? A H2S B NaHSO4 C S D SO2

1 marks

Answer: A

This question in 9701/12 May/June 2014

Q124 · Menthol is a naturally-occurring alcohol found in peppermint oil 9701/12 May/June 2014

38 Menthol is a naturally-occurring alcohol found in peppermint oil. OH menthol Which reagents will react with menthol? 1 aqueous bromine 2 sodium metal 3 aqueous acidified manganate(VII)

1 marks

Answer: C

This question in 9701/12 May/June 2014

Q125 · Which pairs of reagents will take part in a redox reaction under suitable conditions? 9701/12 May/June 2014

39 Which pairs of reagents will take part in a redox reaction under suitable conditions? 1 CH3(CH2)4CHO + Tollens’ reagent 2 CH3(CH2)4CH3 + Br2 3 CH3CO(CH2)4CH3 + Fehling’s reagent

1 marks

Answer: B

This question in 9701/12 May/June 2014

Q126 · The free radical substitution reaction between methane and chlorine involves initiation… 9701/13 May/June 2014

30 The free radical substitution reaction between methane and chlorine involves initiation, propagation and termination stages. Which row is correct? involved in radical produced in initiation stage a propagation stage A heterolytic fission H• B heterolytic fission CH3• C homolytic fission H• D homolytic fission CH3•

1 marks

Answer: D

This question in 9701/13 May/June 2014

Q127 · Many crude oils contain H2S 9701/13 May/June 2014

33 Many crude oils contain H2S. During refining, by the Claus process, the H2S is converted into solid sulfur, which is then removed. reaction I 2H2S(g) + 3O2(g) → 2H2O(l) + 2SO2(g) reaction II 2H2S(g) + SO2(g) → 2H2O(l) + 3S(s) Which statements about the Claus process are correct? 1 H2S is oxidised in reaction I. 2 SO2 oxidises H2S in reaction II. 3 Hydrogen is oxidised in reaction II.

1 marks

Answer: B

This question in 9701/13 May/June 2014

Q128 · Which statements explain why sulfur dioxide is used as a food preservative? 9701/13 May/June 2014

35 Which statements explain why sulfur dioxide is used as a food preservative? 1 It is a reducing agent and therefore an anti-oxidant. 2 It prevents alcohols in foods forming sour-tasting acids. 3 It does not smell and therefore can be used in large quantities.

1 marks

Answer: B

This question in 9701/13 May/June 2014

Q129 · In which reaction does hydrogen behave as an oxidising agent? 9701/11 Oct/Nov 2014

2 In which reaction does hydrogen behave as an oxidising agent? A H2 + Cl 2 → 2HCl B C2H4 + H2 → C2H6 C N2 + 3H2 → 2NH3 D 2Na + H2 → 2NaH

1 marks

Answer: D

This question in 9701/11 Oct/Nov 2014

Q130 · Which property is not associated with the element sodium? 9701/11 Oct/Nov 2014

13 Which property is not associated with the element sodium? A It can react with cold water to form hydrogen. B It forms a basic oxide. C It forms a neutral chloride. D It is an oxidising agent.

1 marks

Answer: D

This question in 9701/11 Oct/Nov 2014

Q131 · Chlorine gas reacts with cold aqueous sodium hydroxide 9701/11 Oct/Nov 2014

16 Chlorine gas reacts with cold aqueous sodium hydroxide. It can also react with hot aqueous sodium hydroxide. What are the oxidation numbers of chlorine in the products of these reactions? cold aqueous hot aqueous sodium hydroxide sodium hydroxide A –1, +1 –1, +5 B –1, +1 +1, +6 C –1, +2 –1, +5 D –1, +2 +1, +6

1 marks

Answer: A

This question in 9701/11 Oct/Nov 2014

Q132 · In which reaction does hydrogen behave as an oxidising agent? 9701/12 Oct/Nov 2014

2 In which reaction does hydrogen behave as an oxidising agent? A H2 + Cl 2 → 2HCl B C2H4 + H2 → C2H6 C N2 + 3H2 → 2NH3 D 2Na + H2 → 2NaH

1 marks

Answer: D

This question in 9701/12 Oct/Nov 2014

Q133 · Chlorine gas reacts with cold aqueous sodium hydroxide 9701/12 Oct/Nov 2014

16 Chlorine gas reacts with cold aqueous sodium hydroxide. It can also react with hot aqueous sodium hydroxide. What are the oxidation numbers of chlorine in the products of these reactions? cold aqueous hot aqueous sodium hydroxide sodium hydroxide A –1, +1 –1, +5 B –1, +1 +1, +6 C –1, +2 –1, +5 D –1, +2 +1, +6

1 marks

Answer: A

This question in 9701/12 Oct/Nov 2014

Q134 · Under standard conditions, which statement is correct? 9701/12 Oct/Nov 2014

17 Under standard conditions, which statement is correct? A Cl –(aq) can oxidise Br2(aq). B Cl –(aq) can reduce Br2(aq). C Cl 2(aq) can oxidise Br –(aq). D Cl 2(aq) can reduce Br –(aq).

1 marks

Answer: C

This question in 9701/12 Oct/Nov 2014

Q135 · Use of the Data Booklet is relevant to this question 9701/13 Oct/Nov 2014

8 Use of the Data Booklet is relevant to this question. Ferrochrome is an alloy of iron and chromium. Ferrochrome can be dissolved in dilute sulfuric acid to produce a mixture of FeSO4 and Cr2(SO4)3. The FeSO4 reacts with K2Cr2O7 in acid solution according to the following equation. 14H+ + 6Fe2+ + Cr2O7 2– → 2Cr3+ + 6Fe3+ + 7H2O When 1.00 g of ferrochrome is dissolved in dilute sulfuric acid, and the resulting solution titrated, 13.1 cm3 of 0.100 mol dm–3 K2Cr2O7 is required for complete reaction. What is the percentage by mass of Fe in the sample of ferrochrome? A 1.22 B 4.39 C 12.2 D 43.9

1 marks

Answer: D

This question in 9701/13 Oct/Nov 2014

Q136 · In a solution that contains both Br2 and Cl 2, a process takes place that produces BrO3… 9701/13 Oct/Nov 2014

31 In a solution that contains both Br2 and Cl 2, a process takes place that produces BrO3 – ions. The process is represented by the following equations. equation 1 Br2 + H2O → HBr + HBrO equation 2 3HBrO + Cl 2 → 2Cl – + BrO3 – + Br2 + 3H+ Which statements about these reactions are correct? 1 Chlorine is reduced in equation 2. 2 Bromine is oxidised in both equation 1 and equation 2. 3 Bromine is reduced in both equation 1 and equation 2.

1 marks

Answer: A

This question in 9701/13 Oct/Nov 2014

Q137 · In oxygen difluoride, OF2, fluorine has an oxidation number of –1 9701/11 May/June 2015

4 In oxygen difluoride, OF2, fluorine has an oxidation number of –1. OF2 will react with sulfur dioxide according to the following equation. OF2 + SO2 → SO3 + F2 What is oxidised and what is reduced in this reaction? oxygen fluorine sulfur in OF2 A oxidised oxidised reduced B oxidised reduced oxidised C reduced oxidised reduced D reduced reduced oxidised

1 marks

Answer: B

This question in 9701/11 May/June 2015

Q138 · Photochromic glass, used for sunglasses, darkens when exposed to bright light and becomes… 9701/12 May/June 2015

10 Photochromic glass, used for sunglasses, darkens when exposed to bright light and becomes more transparent again when the light is less bright. The darkness of the glass is related to the concentration of silver atoms. The following reactions are involved. reaction 1 Ag+ + Cl – Ag + Cl reaction 2 Cu+ + Cl → Cu2+ + Cl – reaction 3 Cu2+ + Ag → Cu+ + Ag+ Which statement about these reactions is correct? A Cu+ and Cu2+ ions act as catalysts. B Cu+ ions act as an oxidising agent in reaction 2. C Reaction 3 increases the darkness of the glass. D Silver atoms are reduced in reaction 3.

1 marks

Answer: A

This question in 9701/12 May/June 2015

Q139 · Carbon monoxide, CO, nitrogen dioxide, NO2, and sulfur dioxide, SO2, are all atmospheric… 9701/12 May/June 2015

18 Carbon monoxide, CO, nitrogen dioxide, NO2, and sulfur dioxide, SO2, are all atmospheric pollutants. Which reaction concerning these compounds occurs in the atmosphere? A CO is spontaneously oxidised to CO2 B NO2 is reduced to NO by CO C NO2 is reduced to NO by SO2 D SO2 is oxidised to SO3 by CO2

1 marks

Answer: C

This question in 9701/12 May/June 2015

Q140 · Chlorate(V) ions, Cl O3 –, are produced in the redox reaction between chlorine and hot… 9701/12 May/June 2015

19 Chlorate(V) ions, Cl O3 –, are produced in the redox reaction between chlorine and hot aqueous sodium hydroxide. Oxidation numbers can be used to help balance the equation for this reaction. What will be the values of coefficients v, x and y in the balanced equation? vCl 2(g) + wOH–(aq) → xCl –(aq) + yCl O3 –(aq) + zH2O(l) v x y A 2 3 1 B 3 4 2 C 3 5 1 D 7 12 2

1 marks

Answer: C

This question in 9701/12 May/June 2015

Q141 · Which of these reactions are redox reactions? 9701/12 May/June 2015

34 Which of these reactions are redox reactions? 1 6NO(g) + 4NH3(g) → 5N2(g) + 6H2O(g) 2 2SO2(g) + O2(g) → 2SO3(g) 3 SO3(g) + H2O(g) → H2SO4(g)

1 marks

Answer: B

This question in 9701/12 May/June 2015

Q142 · Arsenic chloride, AsCl 3, reacts with sodium borohydride, NaBH4 9701/12 Oct/Nov 2015

2 Arsenic chloride, AsCl 3, reacts with sodium borohydride, NaBH4. pAsCl 3 + qNaBH4 → rAsH3 + sNaCl + tBCl 3 What are the numbers p, q, r, s and t when this equation is balanced correctly? p q r s t A 2 3 2 3 1 B 3 3 3 3 2 C 4 3 4 3 3 D 4 4 4 4 3

1 marks

This question in 9701/12 Oct/Nov 2015

Q143 · Calcium forms an ionic compound with carbon, called calcium carbide 9701/12 Oct/Nov 2015

5 Calcium forms an ionic compound with carbon, called calcium carbide. The oxidation number of carbon in calcium carbide is –1. Calcium carbide is readily hydrolysed by water giving two products only. What could be the formulae of calcium carbide and the two products of hydrolysis? calcium carbide products A Ca2C CaO and C2H4 B Ca2C Ca(OH)2 and C2H2 C CaC2 CaO and C2H4 D CaC2 Ca(OH)2 and C2H2

1 marks

This question in 9701/12 Oct/Nov 2015

Q144 · Ammonia and chlorine react in the gas phase 9701/12 Oct/Nov 2015

34 Ammonia and chlorine react in the gas phase. 8NH3 + 3Cl 2 → N2 + 6NH4Cl Which statements are correct? 1 Each nitrogen atom is oxidised. 2 Each chlorine atom is reduced. 3 Ammonia behaves as a base.

1 marks

This question in 9701/12 Oct/Nov 2015

Q145 · Which compound contains two different elements with identical oxidation states? 9701/12 Feb/March 2016

1 Which compound contains two different elements with identical oxidation states? A HCl O B Mg(OH)2 C Na2SO4 D NH4Cl

1 marks

Answer: A

This question in 9701/12 Feb/March 2016

Q146 · After black and white photographic film has been developed, unreacted silver bromide is… 9701/12 Feb/March 2016

19 After black and white photographic film has been developed, unreacted silver bromide is removed by reaction with sodium thiosulfate. AgBr + 2Na2S2O3 → 4Na+ + Br – + [Ag(S2O3)2]3– What is the function of the thiosulfate ion? A to make the silver ions soluble B to oxidise the silver ions C to reduce the bromine D to reduce the silver ions

1 marks

Answer: A

This question in 9701/12 Feb/March 2016

Q147 · A sample containing 0.40 mol of calcium nitrate was decomposed by heating in a roaring… 9701/12 Feb/March 2016

36 A sample containing 0.40 mol of calcium nitrate was decomposed by heating in a roaring Bunsen burner flame until there was no further decomposition. What are the products of this reaction? 1 0.40 mol of calcium oxide 2 0.40 mol of nitrogen, N2(g) 3 0.40 mol of oxygen, O2(g)

1 marks

Answer: D

This question in 9701/12 Feb/March 2016

Q148 · Which pair of reagents will take part in a redox reaction? 9701/11 May/June 2016

22 Which pair of reagents will take part in a redox reaction? A CH3CHCH2 + Br2 B CH3CH2CH2OH + concentrated H3PO4 C CH3COCH3 + HCN D HCO2C2H5 + dilute H2SO4

1 marks

Answer: A

This question in 9701/11 May/June 2016

Q149 · Bromine reacts with water 9701/11 May/June 2016

33 Bromine reacts with water. Br2 + H2O HOBr + HBr Which oxidation states of bromine are present in the equilibrium mixture? 1 +3 2 0 3 –1

1 marks

Answer: C

This question in 9701/11 May/June 2016

Q150 · In the treatment of domestic water supplies, chlorine is added to the water to form HCl O 9701/12 May/June 2016

9 In the treatment of domestic water supplies, chlorine is added to the water to form HCl O. Cl 2(aq) + H2O(I) → H+(aq) + Cl –(aq) + HCl O(aq) The HCl O reacts further to give Cl O– ions. HCl O(aq) + H2O(I) H3O+(aq) + Cl O–(aq) Both HCl O and Cl O– kill bacteria by oxidation. What is the change in oxidation number of chlorine when forming the Cl O– ion from aqueous chlorine? A –1 B 0 C +1 D +2

1 marks

Answer: C

This question in 9701/12 May/June 2016

Q151 · Nitrogen(II) oxide, NO, nitrogen(IV) oxide, NO2, carbon monoxide, CO, and unburnt… 9701/12 May/June 2016

17 Nitrogen(II) oxide, NO, nitrogen(IV) oxide, NO2, carbon monoxide, CO, and unburnt hydrocarbons are present in the exhaust gases of internal combustion engines. When catalytic converters are used to remove these compounds from the exhaust gases, redox reactions occur. What happens to each compound in the catalytic converter? NO NO2 CO hydrocarbons A oxidised oxidised reduced oxidised B oxidised oxidised oxidised oxidised C reduced reduced oxidised oxidised D reduced reduced reduced reduced

1 marks

Answer: C

This question in 9701/12 May/June 2016

Q152 · In which reaction is the organic compound oxidised? 9701/12 May/June 2016

27 In which reaction is the organic compound oxidised? A CH3CH2CH2CHO + Tollens’ reagent B CH3CH2CH2CHO + LiAl H4 C CH3CH2CH2OH + concentrated H3PO4 D CH3CO2C2H5 + dilute H2SO4

1 marks

Answer: A

This question in 9701/12 May/June 2016

Q153 · Sulfur dioxide is used as a preservative in wine making 9701/13 May/June 2016

10 Sulfur dioxide is used as a preservative in wine making. The following equations describe the reactions that occur when sulfur dioxide dissolves in water. H2O + SO2 HSO3 – + H+ HSO3 – + H+ SO3 2– + 2H+ Which statement about these two reactions is correct? A HSO3 – acts as a base. B SO2 acts as an oxidising agent. C SO3 2– acts as an acid. D SO3 2– acts as a reducing agent.

1 marks

Answer: A

This question in 9701/13 May/June 2016

Q154 · When KCl O3 is heated, the following reaction occurs 9701/13 May/June 2016

34 When KCl O3 is heated, the following reaction occurs. 4KCl O3 → 3KCl O4 + KCl Which statements are correct? 1 The oxidation state of Cl in KCl O3 is +5. 2 The oxidation state of some Cl atoms decreases by 6. 3 The reaction involves disproportionation.

1 marks

Answer: A

This question in 9701/13 May/June 2016

Q155 · The reaction between acidified dichromate(VI) ions, Cr2O7 2–, and aqueous Fe2+ ions… 9701/11 Oct/Nov 2016

3 The reaction between acidified dichromate(VI) ions, Cr2O7 2–, and aqueous Fe2+ ions results in the dichromate(VI) ions being reduced to Cr3+ ions. What is the correct equation for this reaction? A Cr2O7 2– + Fe2+ + 14H+ → 2Cr3+ + Fe3+ + 7H2O B Cr2O7 2– + 2Fe2+ + 14H+ → 2Cr3+ + 2Fe3+ + 7H2O C Cr2O7 2– + 3Fe2+ + 14H+ → 2Cr3+ + 3Fe3+ + 7H2O D Cr2O7 2– + 6Fe2+ + 14H+ → 2Cr3+ + 6Fe3+ + 7H2O

1 marks

Answer: D

This question in 9701/11 Oct/Nov 2016

Q156 · Sodium chromate(VI), Na2CrO4, is manufactured by heating chromite, FeCr2O4, with sodium… 9701/11 Oct/Nov 2016

9 Sodium chromate(VI), Na2CrO4, is manufactured by heating chromite, FeCr2O4, with sodium carbonate in an oxidising atmosphere. Chromite contains Cr2O4 2– ions. 2FeCr2O4 + 4Na2CO3 + 3 2 1 O2 → 4Na2CrO4 + Fe2O3 + 4CO2 What happens in this reaction? A Chromium and iron are the only elements oxidised. B Chromium, iron and carbon are oxidised. C Only chromium is oxidised. D Only iron is oxidised.

1 marks

Answer: A

This question in 9701/11 Oct/Nov 2016

Q157 · X, Y and Z represent different halogens 9701/11 Oct/Nov 2016

19 X, Y and Z represent different halogens. The table shows the results of nine experiments in which aqueous solutions of X2, Y2 and Z2 were separately added to separate aqueous solutions containing X –, Y – and Z – ions. X –(aq) Y –(aq) Z –(aq) X2(aq) no reaction no reaction no reaction Y2(aq) X2 formed no reaction Z2 formed Z2(aq) X2 formed no reaction no reaction Which row of the following table contains the ions X –, Y – and Z – in order of their decreasing strength as reducing agents? strongest weakest A X – Y – Z – B X – Z – Y – C Y – Z – X – D Z – X – Y –

1 marks

Answer: B

This question in 9701/11 Oct/Nov 2016

Q158 · The reaction between acidified dichromate(VI) ions, Cr2O7 2–, and aqueous Fe2+ ions… 9701/13 Oct/Nov 2016

3 The reaction between acidified dichromate(VI) ions, Cr2O7 2–, and aqueous Fe2+ ions results in the dichromate(VI) ions being reduced to Cr3+ ions. What is the correct equation for this reaction? A Cr2O7 2– + Fe2+ + 14H+ → 2Cr3+ + Fe3+ + 7H2O B Cr2O7 2– + 2Fe2+ + 14H+ → 2Cr3+ + 2Fe3+ + 7H2O C Cr2O7 2– + 3Fe2+ + 14H+ → 2Cr3+ + 3Fe3+ + 7H2O D Cr2O7 2– + 6Fe2+ + 14H+ → 2Cr3+ + 6Fe3+ + 7H2O

1 marks

Answer: D

This question in 9701/13 Oct/Nov 2016

Q159 · Sodium chromate(VI), Na2CrO4, is manufactured by heating chromite, FeCr2O4, with sodium… 9701/13 Oct/Nov 2016

9 Sodium chromate(VI), Na2CrO4, is manufactured by heating chromite, FeCr2O4, with sodium carbonate in an oxidising atmosphere. Chromite contains Cr2O4 2– ions. 2FeCr2O4 + 4Na2CO3 + 3 2 1 O2 → 4Na2CrO4 + Fe2O3 + 4CO2 What happens in this reaction? A Chromium and iron are the only elements oxidised. B Chromium, iron and carbon are oxidised. C Only chromium is oxidised. D Only iron is oxidised.

1 marks

Answer: A

This question in 9701/13 Oct/Nov 2016

Q160 · X, Y and Z represent different halogens 9701/13 Oct/Nov 2016

19 X, Y and Z represent different halogens. The table shows the results of nine experiments in which aqueous solutions of X2, Y2 and Z2 were separately added to separate aqueous solutions containing X –, Y – and Z – ions. X –(aq) Y –(aq) Z –(aq) X2(aq) no reaction no reaction no reaction Y2(aq) X2 formed no reaction Z2 formed Z2(aq) X2 formed no reaction no reaction Which row of the following table contains the ions X –, Y – and Z – in order of their decreasing strength as reducing agents? strongest weakest A X – Y – Z – B X – Z – Y – C Y – Z – X – D Z – X – Y –

1 marks

Answer: B

This question in 9701/13 Oct/Nov 2016

Q161 · In some fireworks there is a reaction between powdered aluminium and powdered barium… 9701/12 May/June 2017

3 In some fireworks there is a reaction between powdered aluminium and powdered barium nitrate. Heat is evolved, an unreactive gas is produced, and all nitrogen atoms are reduced. What is the equation for this reaction? A 2Al + Ba(NO3)2 → Al 2O3 + BaO + 2NO B 4Al + 4Ba(NO3)2 → 2Al 2O3 + 4Ba(NO2)2 + O2 C 10Al + 3Ba(NO3)2 → 5Al 2O3 + 3BaO + 3N2 D 10Al + 18Ba(NO3)2 → 10Al (NO3)3 + 18BaO + 3N2

1 marks

Answer: C

This question in 9701/12 May/June 2017

Q162 · A reaction sequence is shown 9701/12 May/June 2017

8 A reaction sequence is shown. 1 2 3 4 SO2 SO3 H2SO4 H2S SO2 In each stage of this sequence the sulfur is oxidised, reduced or neither oxidised nor reduced. Which row is correct? 1 2 3 4 A neither oxidised reduced reduced B oxidised neither reduced reduced C oxidised neither reduced oxidised D oxidised oxidised reduced oxidised

1 marks

Answer: C

This question in 9701/12 May/June 2017

Q163 · Element X reacts with cold, dilute, aqueous sodium hydroxide to form two different… 9701/12 May/June 2017

16 Element X reacts with cold, dilute, aqueous sodium hydroxide to form two different chlorine-containing products, Y and Z. What are the oxidation states of chlorine in Y and Z? Y Z A 0 +1 B 0 +5 C –1 +1 D –1 +5

1 marks

Answer: C

This question in 9701/12 May/June 2017

Q164 · Two conversions are shown 9701/13 May/June 2017

4 Two conversions are shown. NH4 + → NH3 C2H4 → C2H6 Which similar feature do these two conversions have? A change in oxidation state of an element B decrease in bond angle C formation of a lone pair of electrons D loss of a π bond

1 marks

Answer: B

This question in 9701/13 May/June 2017

Q165 · Vanadium reacts with dilute sulfuric acid to form V2(SO4)3 and hydrogen gas 9701/13 May/June 2017

7 Vanadium reacts with dilute sulfuric acid to form V2(SO4)3 and hydrogen gas. What happens to vanadium atoms in this reaction? A They lose three electrons and are oxidised. B They lose three electrons and are reduced. C They lose two electrons and are oxidised. D They lose two electrons and are reduced.

1 marks

Answer: A

This question in 9701/13 May/June 2017

Q166 · Na2S2O3 reacts with HCl as shown 9701/13 May/June 2017

8 Na2S2O3 reacts with HCl as shown. Na2S2O3(aq) + 2HCl (aq) → 2NaCl (aq) + H2O(l) + SO2(g) + S(s) When calculating the oxidation number of sulfur in Na2S2O3, the average oxidation number of the two sulfur atoms should be found. What is the oxidation number of sulfur in each of Na2S2O3, SO2, and S? Na2S2O3 SO2 S A +2 +2 +1 B +2 +4 0 C +4 +4 0 D +5 +4 0

1 marks

Answer: B

This question in 9701/13 May/June 2017

Q167 · Which row correctly describes the reactions of calcium and strontium with water? 9701/13 May/June 2017

15 Which row correctly describes the reactions of calcium and strontium with water? substance reduced substance oxidised more vigorous reaction A calcium or strontium water calcium + water B calcium or strontium water strontium + water C water calcium or strontium calcium + water D water calcium or strontium strontium + water

1 marks

Answer: D

This question in 9701/13 May/June 2017

Q168 · Chlorine gas is added to cold, aqueous sodium hydroxide 9701/13 May/June 2017

16 Chlorine gas is added to cold, aqueous sodium hydroxide. In a separate experiment, chlorine gas is added to hot, aqueous sodium hydroxide. Which oxidation states of chlorine are found in the reactants and products of the two reactions that take place? A 0, –1, +1 and +5 B 0, –1 and +1 only C 0, –1 and +5 only D 0, +1 and +5 only

1 marks

Answer: A

This question in 9701/13 May/June 2017

Q169 · Which statements about the atoms 23Na and 24Mg are correct? 9701/13 May/June 2017

31 Which statements about the atoms 23Na and 24Mg are correct? 1 They have the same number of filled electron orbitals. 2 They have the same number of neutrons. 3 They are both reducing agents.

1 marks

Answer: C

This question in 9701/13 May/June 2017

Q170 · One of the reactions in a lead / acid cell is shown 9701/11 Oct/Nov 2017

6 One of the reactions in a lead / acid cell is shown. Pb(s) + PbO2(s) + 4H+(aq) + 2SO4 2–(aq) → 2PbSO4(s) + 2H2O(l) Which statement about this reaction is correct? A Lead is both oxidised and reduced. B Lead is neither oxidised nor reduced. C Lead is oxidised only. D Lead is reduced only.

1 marks

Answer: A

This question in 9701/11 Oct/Nov 2017

Q171 · 71.0 g of chlorine, Cl 2, react with an excess of sodium hydroxide solution at a… 9701/11 Oct/Nov 2017

17 71.0 g of chlorine, Cl 2, react with an excess of sodium hydroxide solution at a particular temperature. The reaction produces exactly 35.5 g of product X. What is product X? A H2O B NaCl C NaCl O D NaCl O3

1 marks

Answer: D

This question in 9701/11 Oct/Nov 2017

Q172 · One way of recovering tin from old printed circuit boards is to dissolve it in a mixture… 9701/11 Oct/Nov 2017

33 One way of recovering tin from old printed circuit boards is to dissolve it in a mixture of concentrated hydrochloric acid and concentrated nitric acid. The tin dissolves because it reacts with the mixture of these concentrated acids. Sn + 4HCl + 2HNO3 → SnCl 4 + NO2 + NO + 3H2O Which statements about this reaction are correct? 1 Nitrogen is present in three different oxidation states in the reactants and products. 2 The oxidation state of tin increases from 0 to +4. 3 The oxidation state of chlorine remains the same.

1 marks

Answer: A

This question in 9701/11 Oct/Nov 2017

Q173 · Which statement is always correct for an oxidation reaction? 9701/12 Oct/Nov 2017

8 Which statement is always correct for an oxidation reaction? A It involves the gain of oxygen by an element. B For one reactant to be oxidised a different reactant must be reduced. C The element or ion being oxidised will gain electrons. D The oxidation number of the element being oxidised will increase.

1 marks

Answer: D

This question in 9701/12 Oct/Nov 2017

Q174 · Hydrogen sulfide can be oxidised to form sulfur dioxide 9701/12 Oct/Nov 2017

33 Hydrogen sulfide can be oxidised to form sulfur dioxide. 2H2S + 3O2 → 2SO2 + 2H2O Which statements are correct? 1 The oxidation number of sulfur increases by 6. 2 The oxidation number of oxygen increases by 2. 3 The oxidation number of hydrogen decreases.

1 marks

Answer: D

This question in 9701/12 Oct/Nov 2017

Q175 · Modern cars are fitted with catalytic converters to reduce atmospheric pollution caused… 9701/12 Oct/Nov 2017

36 Modern cars are fitted with catalytic converters to reduce atmospheric pollution caused by unwanted reactions during the combustion of the fuel. Which statements are correct? 1 Carbon monoxide is oxidised to carbon dioxide in a catalytic converter. 2 Catalytic converters have a very large surface area. 3 Nitrogen dioxide is reduced to nitrogen monoxide in a catalytic converter.

1 marks

Answer: B

This question in 9701/12 Oct/Nov 2017

Q176 · One of the reactions in a lead / acid cell is shown 9701/13 Oct/Nov 2017

6 One of the reactions in a lead / acid cell is shown. Pb(s) + PbO2(s) + 4H+(aq) + 2SO4 2–(aq) → 2PbSO4(s) + 2H2O(l) Which statement about this reaction is correct? A Lead is both oxidised and reduced. B Lead is neither oxidised nor reduced. C Lead is oxidised only. D Lead is reduced only.

1 marks

Answer: A

This question in 9701/13 Oct/Nov 2017

Q177 · One way of recovering tin from old printed circuit boards is to dissolve it in a mixture… 9701/13 Oct/Nov 2017

33 One way of recovering tin from old printed circuit boards is to dissolve it in a mixture of concentrated hydrochloric acid and concentrated nitric acid. The tin dissolves because it reacts with the mixture of these concentrated acids. Sn + 4HCl + 2HNO3 → SnCl 4 + NO2 + NO + 3H2O Which statements about this reaction are correct? 1 Nitrogen is present in three different oxidation states in the reactants and products. 2 The oxidation state of tin increases from 0 to +4. 3 The oxidation state of chlorine remains the same.

1 marks

Answer: A

This question in 9701/13 Oct/Nov 2017

Q178 · Which reaction is not a redox reaction? 9701/12 Feb/March 2018

10 Which reaction is not a redox reaction? A Mg + 2HNO3 → Mg(NO3)2 + H2 B 2Mg(NO3)2 → 2MgO + 4NO2 + O2 C SO2 + NO2 → SO3 + NO D SO3 + H2O → H2SO4

1 marks

Answer: D

This question in 9701/12 Feb/March 2018

Q179 · Bromine is extracted from sea-water 9701/12 Feb/March 2018

17 Bromine is extracted from sea-water. In the final stages of the process two redox reactions take place. Br2(aq) + SO2(g) + 2H2O(l) → 2HBr(aq) + H2SO4(aq) 2HBr(aq) + Cl 2(g) → Br2(g) + 2HCl (aq) Which row is correct? strongest weakest oxidising agent oxidising agent A Br2 SO2 Cl 2 B Cl 2 Br2 SO2 C Cl 2 SO2 Br2 D SO2 Br2 Cl 2

1 marks

Answer: B

This question in 9701/12 Feb/March 2018

Q180 · When burned, sulfur forms a gaseous product X which can be oxidised to produce a gas Y 9701/12 Feb/March 2018

18 When burned, sulfur forms a gaseous product X which can be oxidised to produce a gas Y. Gas Y reacts with water to produce a product Z. Which row correctly shows the oxidation states of sulfur in X, Y and Z? X Y Z A –2 +4 +4 B –2 +4 +6 C +4 +6 +4 D +4 +6 +6

1 marks

Answer: D

This question in 9701/12 Feb/March 2018

Q181 · Ammonia and chlorine react together in the gas phase 9701/12 Feb/March 2018

33 Ammonia and chlorine react together in the gas phase. 8NH3 + 3Cl 2 → N2 + 6NH4Cl Which statements are correct? 1 Ammonia behaves as a reducing agent. 2 Ammonia behaves as a base. 3 The oxidation number of hydrogen changes.

1 marks

Answer: B

This question in 9701/12 Feb/March 2018

Q182 · Chlorine reacts with hot aqueous sodium hydroxide 9701/12 Feb/March 2018

35 Chlorine reacts with hot aqueous sodium hydroxide. Which oxidation states does chlorine show in the products of this reaction? 1 –1 2 +3 3 +1

1 marks

Answer: D

This question in 9701/12 Feb/March 2018

Q183 · In which different forms does nitrogen exist in compounds? 9701/12 Feb/March 2018

36 In which different forms does nitrogen exist in compounds? 1 bonded by a triple covalent bond 2 as part of a cation 3 in an oxidation state of +5

1 marks

Answer: A

This question in 9701/12 Feb/March 2018

Q184 · Ethanedioate ions, C2O4 2–, react with a suitable reagent to form CO2 9701/11 May/June 2018

8 Ethanedioate ions, C2O4 2–, react with a suitable reagent to form CO2. A half-equation for this reaction is shown. C2O4 2– → 2CO2 + 2e– Which row is correct? oxidation state of 2– type of reaction carbon in C2O4 A +3 oxidation B +3 reduction C +5 oxidation D +5 reduction

1 marks

Answer: A

This question in 9701/11 May/June 2018

Q185 · Oxidation numbers should be used to answer this question 9701/11 May/June 2018

9 Oxidation numbers should be used to answer this question. A redox reaction takes place between hydroxylammonium ions, [NH3OH]+, and acidified iron(III) ions, Fe3+. The products are iron(II) ions, Fe2+, H+ ions, water and a compound of nitrogen. The mole ratio of reacting hydroxylammonium ions to reacting iron(III) ions is 1 : 2. Which nitrogen-containing compound could be formed in the reaction? A NH3 B N2O C NO D NO2

1 marks

Answer: B

This question in 9701/11 May/June 2018

Q186 · Chlorine reacts with cold aqueous sodium hydroxide to produce sodium chloride, water and… 9701/11 May/June 2018

14 Chlorine reacts with cold aqueous sodium hydroxide to produce sodium chloride, water and compound X. Chlorine reacts with hot aqueous sodium hydroxide to produce sodium chloride, water and compound Y. What are the oxidation states of chlorine in compound X and compound Y? X Y A –1 –5 B –1 +5 C +1 –5 D +1 +5

1 marks

Answer: D

This question in 9701/11 May/June 2018

Q187 · Each of the three mixtures shown can result in a chemical reaction 9701/11 May/June 2018

35 Each of the three mixtures shown can result in a chemical reaction. Which mixtures result in a redox reaction? 1 bromine + hydrogen 2 sodium chloride + concentrated sulfuric acid 3 potassium iodide + silver nitrate

1 marks

Answer: D

This question in 9701/11 May/June 2018

Q188 · Sulfur reacts with concentrated nitric acid in a redox reaction 9701/12 May/June 2018

8 Sulfur reacts with concentrated nitric acid in a redox reaction. S + 4HNO3 → SO2 + 4NO2 + 2H2O What are the changes in oxidation number of sulfur and of nitrogen in this reaction? sulfur nitrogen A +2 –3 B +2 –1 C +4 –3 D +4 –1

1 marks

Answer: D

This question in 9701/12 May/June 2018

Q189 · Xenon hexafluoride, XeF6, reacts with water 9701/13 May/June 2018

8 Xenon hexafluoride, XeF6, reacts with water. XeF6 + 3H2O → XeO3 + 6HF Which statement is correct? A Hydrogen is reduced in this reaction. B Hydrogen is the only element oxidised in this reaction. C The only element oxidised in this reaction is xenon. D This is not a redox reaction.

1 marks

Answer: D

This question in 9701/13 May/June 2018

Q190 · When calcium and calcium hydride, CaH2, react separately with water, they each produce a… 9701/13 May/June 2018

15 When calcium and calcium hydride, CaH2, react separately with water, they each produce a white solid and a colourless gas. The white solid is the same compound in each reaction. Which statement is correct? A Both Ca and CaH2 produce H2. B Both Ca and CaH2 produce O2. C Ca produces H2 and CaH2 produces O2. D Ca produces O2 and CaH2 produces H2.

1 marks

Answer: A

This question in 9701/13 May/June 2018

Q191 · When concentrated sulfuric acid is added to solid sodium chloride, HCl is formed but not… 9701/13 May/June 2018

16 When concentrated sulfuric acid is added to solid sodium chloride, HCl is formed but not Cl 2. When concentrated sulfuric acid is added to solid sodium iodide, I2 is formed. Which statement explains these observations? A Sulfuric acid is an oxidising agent and chloride ions are more easily oxidised. B Sulfuric acid is an oxidising agent and iodide ions are more easily oxidised. C Sulfuric acid is a reducing agent and chloride ions are more easily reduced. D Sulfuric acid is a reducing agent and iodide ions are more easily reduced.

1 marks

Answer: B

This question in 9701/13 May/June 2018

Q192 · Ammonia and chlorine react as shown 9701/13 May/June 2018

33 Ammonia and chlorine react as shown. 8NH3 + 3Cl 2 → N2 + 6NH4Cl Which statements are correct? 1 Each nitrogen atom is oxidised. 2 Each chlorine atom is reduced. 3 Ammonia behaves as a base.

1 marks

Answer: C

This question in 9701/13 May/June 2018

Q193 · Nitric acid is known to take part in the oxidation of atmospheric sulfur dioxide 9701/11 Oct/Nov 2018

7 Nitric acid is known to take part in the oxidation of atmospheric sulfur dioxide. One possible reaction is shown. SO2 + HNO3 → NO+ + HSO4 – Which row shows the correct changes in oxidation numbers of nitrogen and sulfur? nitrogen sulfur A –3 +3 B –2 +2 C –2 +3 D –1 +2

1 marks

Answer: B

This question in 9701/11 Oct/Nov 2018

Q194 · A transition metal ion, M2+, reacts with acidified dichromate(VI) ions to form M4+ ions… 9701/11 Oct/Nov 2018

8 A transition metal ion, M2+, reacts with acidified dichromate(VI) ions to form M4+ ions, Cr3+ ions, and H2O. Which equation correctly represents this reaction? A Cr2O7 2– + 14H+ + M2+ → 2Cr3+ + 7H2O + M4+ B Cr2O7 2– + 14H+ + 2M2+ → 2Cr3+ + 7H2O + 2M4+ C Cr2O7 2– + 14H+ + 3M2+ → 2Cr3+ + 7H2O + 3M4+ D Cr2O7 2– + 14H+ + 6M2+ → 2Cr3+ + 7H2O + 6M4+

1 marks

Answer: C

This question in 9701/11 Oct/Nov 2018

Q195 · Reaction 1: chlorine reacts with cold aqueous sodium hydroxide to form solution Z 9701/11 Oct/Nov 2018

17 Reaction 1: chlorine reacts with cold aqueous sodium hydroxide to form solution Z. Reaction 2: solution Z is heated and forms Cl O3 –(aq) and Cl –(aq). Which equations represent reaction 1 and reaction 2? A reaction 1 2Cl 2 + 4OH– → Cl O2 – + 3Cl – + 2H2O reaction 2 3Cl O2 – → 2Cl O3 – + Cl – B reaction 1 2Cl 2 + 4OH– → Cl O2 – + 3Cl – + 2H2O reaction 2 3Cl O– → Cl O3 – + 2Cl – C reaction 1 Cl 2 + 2OH– → Cl O– + Cl – + H2O reaction 2 2Cl O– + 2OH– → Cl O3 – + Cl – + H2O D reaction 1 Cl 2 + 2OH– → Cl O– + Cl – + H2O reaction 2 3Cl O– → Cl O3 – + 2Cl –

1 marks

Answer: D

This question in 9701/11 Oct/Nov 2018

Q196 · Ammonium metavanadate, NH4VO3, can be used to make a solution containing VO2Cl, which… 9701/12 Oct/Nov 2018

8 Ammonium metavanadate, NH4VO3, can be used to make a solution containing VO2Cl, which contains chloride ions. What is the change in the oxidation number of vanadium in this reaction? A –1 B 0 C +1 D +2

1 marks

Answer: B

This question in 9701/12 Oct/Nov 2018

Q197 · Chlorine reacts with both hot and cold sodium hydroxide to form products containing… 9701/12 Oct/Nov 2018

17 Chlorine reacts with both hot and cold sodium hydroxide to form products containing chlorine. Cold sodium hydroxide forms sodium chlorate(X) and hot sodium hydroxide forms sodium chlorate(Y). X and Y are oxidation numbers. Which equation is correct? A Y = X – 6 B Y = X – 4 C Y = X + 4 D Y = X + 6

1 marks

Answer: C

This question in 9701/12 Oct/Nov 2018

Q198 · Aqueous iron(II) sulfate can take part in redox reactions 9701/12 Oct/Nov 2018

33 Aqueous iron(II) sulfate can take part in redox reactions. 6FeSO4 + 7H2SO4 + Na2Cr2O7 → 3Fe2(SO4)3 + Cr2(SO4)3 + Na2SO4 + 7H2O Which redox changes occur during this reaction? 1 Fe(II) is oxidised to Fe(III). 2 Cr(VI) is reduced to Cr(III). 3 Oxygen is reduced to water.

1 marks

Answer: B

This question in 9701/12 Oct/Nov 2018

Q199 · Nitric acid is known to take part in the oxidation of atmospheric sulfur dioxide 9701/13 Oct/Nov 2018

7 Nitric acid is known to take part in the oxidation of atmospheric sulfur dioxide. One possible reaction is shown. SO2 + HNO3 → NO+ + HSO4 – Which row shows the correct changes in oxidation numbers of nitrogen and sulfur? nitrogen sulfur A –3 +3 B –2 +2 C –2 +3 D –1 +2

1 marks

Answer: B

This question in 9701/13 Oct/Nov 2018

Q200 · A transition metal ion, M2+, reacts with acidified dichromate(VI) ions to form M4+ ions… 9701/13 Oct/Nov 2018

8 A transition metal ion, M2+, reacts with acidified dichromate(VI) ions to form M4+ ions, Cr3+ ions, and H2O. Which equation correctly represents this reaction? A Cr2O7 2– + 14H+ + M2+ → 2Cr3+ + 7H2O + M4+ B Cr2O7 2– + 14H+ + 2M2+ → 2Cr3+ + 7H2O + 2M4+ C Cr2O7 2– + 14H+ + 3M2+ → 2Cr3+ + 7H2O + 3M4+ D Cr2O7 2– + 14H+ + 6M2+ → 2Cr3+ + 7H2O + 6M4+

1 marks

Answer: C

This question in 9701/13 Oct/Nov 2018

Q201 · Reaction 1: chlorine reacts with cold aqueous sodium hydroxide to form solution Z 9701/13 Oct/Nov 2018

17 Reaction 1: chlorine reacts with cold aqueous sodium hydroxide to form solution Z. Reaction 2: solution Z is heated and forms Cl O3 –(aq) and Cl –(aq). Which equations represent reaction 1 and reaction 2? A reaction 1 2Cl 2 + 4OH– → Cl O2 – + 3Cl – + 2H2O reaction 2 3Cl O2 – → 2Cl O3 – + Cl – B reaction 1 2Cl 2 + 4OH– → Cl O2 – + 3Cl – + 2H2O reaction 2 3Cl O– → Cl O3 – + 2Cl – C reaction 1 Cl 2 + 2OH– → Cl O– + Cl – + H2O reaction 2 2Cl O– + 2OH– → Cl O3 – + Cl – + H2O D reaction 1 Cl 2 + 2OH– → Cl O– + Cl – + H2O reaction 2 3Cl O– → Cl O3 – + 2Cl –

1 marks

Answer: D

This question in 9701/13 Oct/Nov 2018

Q202 · Acidified potassium manganate(VII) reacts with iron(II) ethanedioate, FeC2O4 9701/12 Feb/March 2019

10 Acidified potassium manganate(VII) reacts with iron(II) ethanedioate, FeC2O4. The reactions taking place are shown. MnO4 – + 8H+ + 5e– → Mn2+ + 4H2O Fe2+ → Fe3+ + e– C2O4 2– → 2CO2 + 2e– How many moles of iron(II) ethanedioate react with one mole of potassium manganate(VII)? A 0.60 B 1.67 C 2.50 D 5.00

1 marks

Answer: B

This question in 9701/12 Feb/March 2019

Q203 · Under standard conditions, which statement is correct? 9701/12 Feb/March 2019

18 Under standard conditions, which statement is correct? A Cl 2(aq) can oxidise Br –(aq). B Cl 2(aq) can reduce Br –(aq). C Cl –(aq) can oxidise Br2(aq). D Cl –(aq) can reduce Br2(aq).

1 marks

Answer: A

This question in 9701/12 Feb/March 2019

Q204 · Ammonia, NH3, and hydrazine, NH2NH2, are two compounds of nitrogen, N2 9701/12 Feb/March 2019

19 Ammonia, NH3, and hydrazine, NH2NH2, are two compounds of nitrogen, N2. Which statement is correct? A The N–N bond in NH2NH2 is polar. B NH3 and NH2NH2 have lone pairs of electrons but N2 does not. C The oxidation number of each nitrogen in NH2NH2 is +2. D The reaction of nitrogen with hydrogen has a high activation energy.

1 marks

Answer: D

This question in 9701/12 Feb/March 2019

Q205 · In which reactions is the underlined element or compound reduced? 9701/12 Feb/March 2019

33 In which reactions is the underlined element or compound reduced? 1 NaCl O + H2O2 → O2 + NaCl + H2O 2 2NH3 + 2Li → 2LiNH2 + H2 3 3CH3CH2OH + K2Cr2O7 + 4H2SO4 → 3CH3CHO + Cr2(SO4)3 + K2SO4 + 7H2O

1 marks

Answer: D

This question in 9701/12 Feb/March 2019

Q206 · Ethanedioic acid, HO2CCO2H, can be oxidised by KMnO4 in dilute sulfuric acid 9701/11 May/June 2019

9 Ethanedioic acid, HO2CCO2H, can be oxidised by KMnO4 in dilute sulfuric acid. The products of this reaction are carbon dioxide, water, potassium sulfate and manganese(II) sulfate. In this reaction each ethanedioic acid molecule loses two electrons as it is oxidised. A half-equation for this process is shown. HO2CCO2H → 2CO2 + 2H+ + 2e– How many water molecules are produced when five ethanedioic acid molecules are oxidised by KMnO4 in dilute sulfuric acid? A 5 B 8 C 10 D 16

1 marks

Answer: B

This question in 9701/11 May/June 2019

Q207 · Concentrated sulfuric acid is added to separate solid samples of sodium chloride, sodium… 9701/11 May/June 2019

16 Concentrated sulfuric acid is added to separate solid samples of sodium chloride, sodium bromide and sodium iodide. With which samples does sulfuric acid act as an oxidising agent? A sodium chloride only B sodium chloride and sodium bromide C sodium bromide and sodium iodide D sodium iodide only

1 marks

Answer: C

This question in 9701/11 May/June 2019

Q208 · X is either chlorine or an oxide of chlorine 9701/12 May/June 2019

9 X is either chlorine or an oxide of chlorine. X reacts with water, under suitable conditions, to form the two acids HCl and HCl O3 in the mole ratio of 1 (HCl ) : 5 (HCl O3). What could be X? A Cl 2 B Cl 2O C Cl O2 D Cl 2O7

1 marks

Answer: C

This question in 9701/12 May/June 2019

Q209 · Which reaction gives a product that is an atmospheric pollutant causing acid rain? 9701/12 May/June 2019

19 Which reaction gives a product that is an atmospheric pollutant causing acid rain? A 3Mg(s) + SO2(g) → MgS(s) + 2MgO(s) B (NH4)2SO4(s) + Ca(OH)2(s) → 2NH3(g) + CaSO4(s) + 2H2O(l) C 2MnO4 –(aq) + 5SO2(g) + 2H2O(l) → 2Mn2+(aq) + 4H+(aq) + 5SO4 2–(aq) D 2FeSO4(s) → Fe2O3(s) + SO2(g) + SO3(g)

1 marks

Answer: D

This question in 9701/12 May/June 2019

Q210 · When O2 reacts with H2S the products are SO2 and H2O 9701/12 May/June 2019

31 When O2 reacts with H2S the products are SO2 and H2O. Mixture Y contains an equal number of the two molecules shown, and no other molecules. 16 O = 18 O H 1 – 32 S – H 1 8 8 1 16 1 Which statements about Y are correct? 1 The average Mr in Y is 34. 2 If some oxygen molecules are removed from Y, the average Mr of the mixture remains the same. 3 When mixture Y is ignited, some H2S remains unreacted.

1 marks

Answer: A

This question in 9701/12 May/June 2019

Q211 · In which reactions are nitrogen atoms reduced? 9701/12 May/June 2019

33 In which reactions are nitrogen atoms reduced? 1 2NO2 → N2 + 2O2 2 4NO2 → 2N2O + 3O2 3 4NO2 + 6H2O → 4NH3 + 7O2

1 marks

Answer: A

This question in 9701/12 May/June 2019

Q212 · A small quantity of hot, concentrated sulfuric acid is added separately to solid samples… 9701/12 May/June 2019

36 A small quantity of hot, concentrated sulfuric acid is added separately to solid samples of potassium halides, KX. Which potassium halides react and produce a mixture of products that include a halogen, X2? 1 potassium iodide 2 potassium bromide 3 potassium chloride

1 marks

Answer: B

This question in 9701/12 May/June 2019

Q213 · Manganese and nitrogen can show a range of different oxidation states 9701/13 May/June 2019

1 Manganese and nitrogen can show a range of different oxidation states. Calculate the sum of the oxidation states of Mn and N in each row of the table. In which row is this sum the smallest? manganese-containing nitrogen-containing species species A MnCl 4 N2 B MnCO3 NO2 – C K2MnO4 NH4 + D Mn(OH)3 NH2OH

1 marks

Answer: D

This question in 9701/13 May/June 2019

Q214 · Ethanol can be oxidised to ethanal by dilute acidified dichromate(VI) ions 9701/13 May/June 2019

8 Ethanol can be oxidised to ethanal by dilute acidified dichromate(VI) ions. The oxidation reaction equation is C2H5OH → C2H4O + 2H+ + 2e–. The reduction reaction equation is Cr2O7 2– + 14H+ + 6e– → 2Cr3+ + 7H2O. Which equation is correct? A Cr2O7 2– + 8H+ + 3C2H5OH → 2Cr3+ + 7H2O + 3C2H4O B Cr2O7 2– + 12H+ + C2H5OH → 2Cr3+ + 7H2O + C2H4O C Cr2O7 2– + 12H+ + 3C2H5OH → 2Cr3+ + 6H2O + 3C2H4O D Cr2O7 2– + 14H+ + 3C2H5OH → 2Cr3+ + 6H2O + 3C2H4O

1 marks

Answer: A

This question in 9701/13 May/June 2019

Q215 · What is the oxidation number of sulfur in each species? 9701/11 Oct/Nov 2019

6 What is the oxidation number of sulfur in each species? H2S SO2 H2SO3 A –2 +4 +4 B –2 +4 +6 C +2 –4 +4 D +2 –4 +6

1 marks

Answer: A

This question in 9701/11 Oct/Nov 2019

Q216 · In the chemical equation, w, x, y and z are all whole numbers 9701/11 Oct/Nov 2019

9 In the chemical equation, w, x, y and z are all whole numbers. wCl O3 – + xMnO4 – + yH+ → wCl O4 – + xMnO2 + zH2O When the equation is balanced, what are w, x and y? w x y A 1 1 2 B 2 2 2 C 2 3 8 D 3 2 2

1 marks

Answer: D

This question in 9701/11 Oct/Nov 2019

Q217 · (NH4)2Cr2O7 decomposes when heated 9701/12 Oct/Nov 2019

8 (NH4)2Cr2O7 decomposes when heated. (NH4)2Cr2O7 → N2 + 4H2O + Cr2O3 Which element is oxidised and which element is reduced? oxidised reduced A chromium nitrogen B hydrogen chromium C nitrogen chromium D nitrogen hydrogen

1 marks

Answer: C

This question in 9701/12 Oct/Nov 2019

Q218 · When lead(II) sulfide, PbS, is heated in air, sulfur dioxide and lead(II) oxide are formed 9701/12 Oct/Nov 2019

9 When lead(II) sulfide, PbS, is heated in air, sulfur dioxide and lead(II) oxide are formed. What is the equation for the reaction between PbS and oxygen? A PbS + 2O2 → SO2 + PbO2 B PbS + 2 2 1 O2 → SO3 + PbO2 C PbS + 1 2 1 O2 → SO2 + PbO D PbS + 2O2 → SO3 + PbO

1 marks

Answer: C

This question in 9701/12 Oct/Nov 2019

Q219 · Chlorate(V) ions, Cl O3 –, are produced in the redox reaction between chlorine and hot… 9701/12 Oct/Nov 2019

15 Chlorate(V) ions, Cl O3 –, are produced in the redox reaction between chlorine and hot aqueous sodium hydroxide. Oxidation numbers can be used to help balance the equation for this reaction. vCl 2(g) + wOH–(aq) → xCl –(aq) + yCl O3 –(aq) + zH2O(l) What are the values of v, x and y in the balanced equation? v x y A 2 3 1 B 3 4 2 C 3 5 1 D 7 12 2

1 marks

Answer: C

This question in 9701/12 Oct/Nov 2019

Q220 · Solid sodium iodide reacts with concentrated sulfuric acid to form more than one product… 9701/12 Oct/Nov 2019

17 Solid sodium iodide reacts with concentrated sulfuric acid to form more than one product that contains sulfur. What is the lowest oxidation number of sulfur in these products? A –2 B 0 C +4 D +6

1 marks

Answer: A

This question in 9701/12 Oct/Nov 2019

Q221 · What is the oxidation number of sulfur in each species? 9701/13 Oct/Nov 2019

6 What is the oxidation number of sulfur in each species? H2S SO2 H2SO3 A –2 +4 +4 B –2 +4 +6 C +2 –4 +4 D +2 –4 +6

1 marks

Answer: A

This question in 9701/13 Oct/Nov 2019

Q222 · In the chemical equation, w, x, y and z are all whole numbers 9701/13 Oct/Nov 2019

9 In the chemical equation, w, x, y and z are all whole numbers. wCl O3 – + xMnO4 – + yH+ → wCl O4 – + xMnO2 + zH2O When the equation is balanced, what are w, x and y? w x y A 1 1 2 B 2 2 2 C 2 3 8 D 3 2 2

1 marks

Answer: D

This question in 9701/13 Oct/Nov 2019

Q223 · In the redox reaction shown, how do the oxidation states of vanadium and sulfur change? 9701/12 Feb/March 2020

5 In the redox reaction shown, how do the oxidation states of vanadium and sulfur change? VO2 + + SO2 → V3+ + SO4 2– vanadium sulfur from to from to A +1 +3 0 –2 B +1 +3 +4 +6 C +5 +3 0 –2 D +5 +3 +4 +6

1 marks

Answer: D

This question in 9701/12 Feb/March 2020

Q224 · When the equation is correctly balanced, what is the value of c? 9701/12 Feb/March 2020

10 When the equation is correctly balanced, what is the value of c? aC2H4 + bH2O + cH+ + 2MnO4 – → dC2H6O2 + eMn2+ A 3 B 4 C 5 D 6

1 marks

Answer: D

This question in 9701/12 Feb/March 2020

Q225 · Hot aqueous sodium hydroxide reacts with chlorine 9701/12 Feb/March 2020

14 Hot aqueous sodium hydroxide reacts with chlorine. 6NaOH(aq) + 3Cl 2(g) → 5NaCl (aq) + NaCl O3(aq) + 3H2O(I) Which statement is correct? A The oxidation numbers of chlorine and hydrogen both change in the reaction. B The oxidation numbers of chlorine in the products are –1 and +1. C If the aqueous sodium hydroxide is cold the reaction produces NaCl O instead of NaCl O3. D Sodium undergoes disproportionation in this reaction.

1 marks

Answer: C

This question in 9701/12 Feb/March 2020

Q226 · How does concentrated sulfuric acid behave when it reacts with sodium chloride? 9701/12 Feb/March 2020

18 How does concentrated sulfuric acid behave when it reacts with sodium chloride? A as an acid only B as an acid and oxidising agent C as an oxidising agent only D as a reducing agent only

1 marks

Answer: A

This question in 9701/12 Feb/March 2020

Q227 · Cobalt can form the positive ion Co(NH3)4Cl 2 + 9701/11 May/June 2020

2 Cobalt can form the positive ion Co(NH3)4Cl 2 +. What is the oxidation number of cobalt in this ion? A +1 B +2 C +3 D +6

1 marks

Answer: C

This question in 9701/11 May/June 2020

Q228 · In this question you should use changes in oxidation numbers to balance a chemical… 9701/11 May/June 2020

8 In this question you should use changes in oxidation numbers to balance a chemical equation. Acidified potassium dichromate(VI) solution can oxidise a solution of V2+ ions. The equation for this reaction is shown. a Cr2O7 2– + b V2+ + c H+ → d Cr3+ + e VO3 – + f H2O What is the ratio a : b in the correctly balanced equation? A 1 : 1 B 1 : 2 C 2 : 1 D 4 : 1

1 marks

Answer: B

This question in 9701/11 May/June 2020

Q229 · Carbon monoxide burns readily in oxygen to form carbon dioxide 9701/11 May/June 2020

34 Carbon monoxide burns readily in oxygen to form carbon dioxide. What does this information suggest? 1 The +4 oxidation state of carbon is more stable than the +2 state. 2 The standard enthalpy change of formation of carbon dioxide is more negative than the standard enthalpy change of formation of carbon monoxide. 3 The value of the equilibrium constant for the reaction, 2CO(g) + O2(g) 2CO2(g), is likely to be high.

1 marks

Answer: A

This question in 9701/11 May/June 2020

Q230 · The catalytic converters fitted to cars remove pollutants from the exhaust gases 9701/11 May/June 2020

35 The catalytic converters fitted to cars remove pollutants from the exhaust gases. Some of the reactions that occur involve oxygen, which comes from the air. Which pollutants in the exhaust gases will react with oxygen on the surface of the catalytic converter? 1 NO2 2 unburnt fuel 3 CO

1 marks

Answer: C

This question in 9701/11 May/June 2020

Q231 · Chlorine reacts with sodium hydroxide in two different ways depending upon the temperature 9701/11 May/June 2020

36 Chlorine reacts with sodium hydroxide in two different ways depending upon the temperature. reaction 1 Cl 2 + 2OH– → Cl – + Cl O– + H2O reaction 2 3Cl 2 + 6OH– → 5Cl – + Cl O3 – + 3H2O Which statements about these reactions are correct? 1 Reaction 2 requires a higher temperature than reaction 1. 2 The products of reaction 1 show chlorine in two different oxidation states. 3 The products of reaction 2 show oxygen in two different oxidation states.

1 marks

Answer: B

This question in 9701/11 May/June 2020

Q232 · In which of the reactions is the organic compound oxidised by the given reagent? 9701/11 May/June 2020

37 In which of the reactions is the organic compound oxidised by the given reagent? 1 CH3CHO + HCN reagent 2 CH3CH2CH2CHO + Tollens’ reagent 3 CH3CH2CHO + Fehling’s reagent

1 marks

Answer: C

This question in 9701/11 May/June 2020

Q233 · In this question you should use changes in oxidation numbers to balance a chemical… 9701/12 May/June 2020

5 In this question you should use changes in oxidation numbers to balance a chemical equation. The following reaction occurs when MnO2 is warmed with dilute H2SO4. a MnO2 + b H+ → c Mn2+ + d MnO4 – + e H2O What is the ratio of c : d in the correctly balanced equation? A 1 : 1 B 1 : 2 C 2 : 3 D 3 : 2

1 marks

Answer: D

This question in 9701/12 May/June 2020

Q234 · In which reaction does an element undergo the largest change in oxidation number? 9701/12 May/June 2020

10 In which reaction does an element undergo the largest change in oxidation number? A Cl 2 + 2OH– → OCl – + Cl – + H2O B 3Cl 2 + 6OH– → Cl O3 – + 5Cl – + 3H2O C Cr2O7 2– + 6Fe2+ + 14H+ → 2Cr3+ + 6Fe3+ + 7H2O D 3MnO4 2– + 4H+ → MnO2 + 2MnO4 – + 2H2O

1 marks

Answer: B

This question in 9701/12 May/June 2020

Q235 · Nitrogen reacts with oxygen to form nitrogen monoxide, NO, and nitrogen dioxide, NO2 9701/13 May/June 2020

5 Nitrogen reacts with oxygen to form nitrogen monoxide, NO, and nitrogen dioxide, NO2. Nitrogen dioxide reacts with water and with hydroxide ions. N2(g) + O2(g) → 2NO(g) 2NO(g) + O2(g) → 2NO2(g) 2NO2(g) + H2O(l) → HNO2(aq) + H+(aq) + NO3 –(aq) 2NO2(g) + 2OH–(aq) → NO2 –(aq) + NO3 –(aq) + H2O(l) What can be deduced using only the information from these equations? A HNO2 is a strong acid. B HNO3 is a weak acid. C NO2 is a neutral gas. D NO is a reducing agent.

1 marks

Answer: D

This question in 9701/13 May/June 2020

Q236 · When solid KCl O3 is heated in the absence of air, a mixture of two chlorine compounds in… 9701/13 May/June 2020

10 When solid KCl O3 is heated in the absence of air, a mixture of two chlorine compounds in the mole ratio of 3 : 1 is formed. Chlorine is the only element whose oxidation number changes in this reaction. What could be the oxidation numbers of chlorine in the two compounds that are formed? A +3 and –1 B +6 and +4 C +7 and –1 D +7 and +1

1 marks

Answer: C

This question in 9701/13 May/June 2020

Q237 · Which element, when burned in oxygen, can form an oxide that is a reducing agent? 9701/13 May/June 2020

15 Which element, when burned in oxygen, can form an oxide that is a reducing agent? A Na B Mg C Al D S

1 marks

Answer: D

This question in 9701/13 May/June 2020

Q238 · Nitrogen oxides are removed from the exhaust gases of internal combustion engines by the… 9701/13 May/June 2020

16 Nitrogen oxides are removed from the exhaust gases of internal combustion engines by the action of a catalyst in a catalytic converter. Which row is correct? change in oxidation type of catalyst number of nitrogen A decrease heterogeneous B decrease homogeneous C increase heterogeneous D increase homogeneous

1 marks

Answer: A

This question in 9701/13 May/June 2020

Q239 · In which reaction does the greatest change in the oxidation number of sulfur occur? 9701/11 Oct/Nov 2020

8 In which reaction does the greatest change in the oxidation number of sulfur occur? A S(s) + O2(g)  SO2(g) B SO2(g) + 2 1O2(g) SO3(g) C SO3(g) + H2SO4(l)  H2S2O7(l) D H2S2O7(l) + H2O(l)  2H2SO4(l)

1 marks

Answer: A

This question in 9701/11 Oct/Nov 2020

Q240 · The first stage in the chloride process for the manufacture of titanium consists of the… 9701/11 Oct/Nov 2020

9 The first stage in the chloride process for the manufacture of titanium consists of the following reaction. 2TiO2 + 4Cl 2 + 3C  2TiCl 4 + 2CO + CO2 What is reduced in this reaction? A carbon B chlorine C oxygen D titanium

1 marks

Answer: B

This question in 9701/11 Oct/Nov 2020

Q241 · With which compound does concentrated sulfuric acid react both as a strong acid and as an… 9701/11 Oct/Nov 2020

16 With which compound does concentrated sulfuric acid react both as a strong acid and as an oxidising agent? A magnesium carbonate B potassium chloride C sodium bromide D sulfur trioxide

1 marks

Answer: C

This question in 9701/11 Oct/Nov 2020

Q242 · Nitrogen forms a number of oxides 9701/11 Oct/Nov 2020

31 Nitrogen forms a number of oxides. Their enthalpies of formation are given. [NO(g)] = +90 kJ mol–1 [N2O(g)] = +82 kJ mol–1 [NO2(g)] = +33 kJ mol–1 Which statements are correct? 1 If N2O(g) is oxidised by O2(g) to NO2(g), 16 kJ is released per mole of N2O. 2 The decomposition of N2O(g) to N2(g) and O2(g) is exothermic. 3 The reaction between NO and oxygen is exothermic.

1 marks

Answer: A

This question in 9701/11 Oct/Nov 2020

Q243 · What is the average oxidation number of sulfur in each compound? 9701/12 Oct/Nov 2020

1 What is the average oxidation number of sulfur in each compound? Ca(HSO3)2 Na2S2O3 A 4 2 B 4 4 C 6 2 D 6 4

1 marks

Answer: A

This question in 9701/12 Oct/Nov 2020

Q244 · Chlorine dioxide, Cl O2, reacts with sodium hydroxide in the reaction shown 9701/12 Oct/Nov 2020

9 Chlorine dioxide, Cl O2, reacts with sodium hydroxide in the reaction shown. 2Cl O2 + 2OH– → Cl O2 – + Cl O3 – + H2O Which statement correctly describes this redox reaction? A Chlorine atoms are oxidised and oxygen atoms are reduced. B Chlorine atoms are reduced and oxygen atoms are oxidised. C Some chlorine atoms are oxidised and some chlorine atoms are reduced. D Some oxygen atoms are oxidised and some oxygen atoms are reduced.

1 marks

Answer: C

This question in 9701/12 Oct/Nov 2020

Q245 · In which reaction does the greatest change in the oxidation number of sulfur occur? 9701/13 Oct/Nov 2020

8 In which reaction does the greatest change in the oxidation number of sulfur occur? A S(s) + O2(g)  SO2(g) B SO2(g) + 2 1O2(g) SO3(g) C SO3(g) + H2SO4(l)  H2S2O7(l) D H2S2O7(l) + H2O(l)  2H2SO4(l)

1 marks

Answer: A

This question in 9701/13 Oct/Nov 2020

Q246 · The first stage in the chloride process for the manufacture of titanium consists of the… 9701/13 Oct/Nov 2020

9 The first stage in the chloride process for the manufacture of titanium consists of the following reaction. 2TiO2 + 4Cl 2 + 3C  2TiCl 4 + 2CO + CO2 What is reduced in this reaction? A carbon B chlorine C oxygen D titanium

1 marks

Answer: B

This question in 9701/13 Oct/Nov 2020

Q247 · With which compound does concentrated sulfuric acid react both as a strong acid and as an… 9701/13 Oct/Nov 2020

16 With which compound does concentrated sulfuric acid react both as a strong acid and as an oxidising agent? A magnesium carbonate B potassium chloride C sodium bromide D sulfur trioxide

1 marks

Answer: C

This question in 9701/13 Oct/Nov 2020

Q248 · Nitrogen forms a number of oxides 9701/13 Oct/Nov 2020

31 Nitrogen forms a number of oxides. Their enthalpies of formation are given. [NO(g)] = +90 kJ mol–1 [N2O(g)] = +82 kJ mol–1 [NO2(g)] = +33 kJ mol–1 Which statements are correct? 1 If N2O(g) is oxidised by O2(g) to NO2(g), 16 kJ is released per mole of N2O. 2 The decomposition of N2O(g) to N2(g) and O2(g) is exothermic. 3 The reaction between NO and oxygen is exothermic.

1 marks

Answer: A

This question in 9701/13 Oct/Nov 2020

Q249 · VO2Cl reacts with NaI under acidic conditions 9701/12 Feb/March 2021

8 VO2Cl reacts with NaI under acidic conditions. 2VO2Cl + 2H2SO4 + 2NaI  VOCl 2 + VOSO4 + I2 + Na2SO4 + 2H2O The oxidation state of Cl is –1 in VO2Cl and in VOCl 2. Which row about this reaction is correct? vanadium iodine A is oxidised is oxidised B is oxidised is reduced C is reduced is oxidised D is reduced is reduced

1 marks

Answer: C

This question in 9701/12 Feb/March 2021

Q250 · Chlorine gas is reacted with aqueous sodium hydroxide 9701/12 Feb/March 2021

16 Chlorine gas is reacted with aqueous sodium hydroxide. The oxidation number of chlorine changes from 0 to –1 and also from 0 to +1. Under which conditions does this reaction occur and what is the colour of the solid silver salt with chlorine in the oxidation state –1? reaction conditions colour of silver salt A cold, dilute alkali white B cold, dilute alkali yellow C hot, concentrated alkali white D hot, concentrated alkali yellow

1 marks

Answer: A

This question in 9701/12 Feb/March 2021

Q251 · When concentrated sulfuric acid reacts with sodium iodide the products include sulfur… 9701/12 Feb/March 2021

17 When concentrated sulfuric acid reacts with sodium iodide the products include sulfur, iodine, hydrogen sulfide and sulfur dioxide. Which statement is correct? A Hydrogen sulfide is the product of a reduction reaction. B Iodide ions are stronger oxidising agents than sulfate ions. C Sulfur atoms from the sulfuric acid are both oxidised and reduced. D Sulfur atoms from the sulfuric acid are oxidised to make sulfur dioxide.

1 marks

Answer: A

This question in 9701/12 Feb/March 2021

Q252 · NO, NO2, CO and unburnt hydrocarbons are present in the exhaust gases of internal… 9701/12 Feb/March 2021

18 NO, NO2, CO and unburnt hydrocarbons are present in the exhaust gases of internal combustion engines. When catalytic converters are used to remove these compounds from the exhaust gases, redox reactions occur. What happens to each compound in the catalytic converter? unburnt NO NO2 CO hydrocarbons A oxidised oxidised reduced oxidised B oxidised oxidised oxidised oxidised C reduced reduced oxidised oxidised D reduced reduced reduced reduced

1 marks

Answer: C

This question in 9701/12 Feb/March 2021

Q253 · When hydrogen iodide is reacted with concentrated sulfuric acid, several reactions occur… 9701/11 May/June 2021

9 When hydrogen iodide is reacted with concentrated sulfuric acid, several reactions occur, including: 8HI + H2SO4  H2S + 4H2O + 4I2 Which row gives the change in oxidation number of iodine and of sulfur in this reaction? change in oxidation change in oxidation number of iodine number of sulfur A –1 +6 B –1 +8 C +1 –6 D +1 –8

1 marks

Answer: D

This question in 9701/11 May/June 2021

Q254 · When an organic compound is oxidised, any oxygen atom gained by the organic molecule is… 9701/11 May/June 2021

25 When an organic compound is oxidised, any oxygen atom gained by the organic molecule is considered to be from a water molecule also producing 2H+ + 2e–. Any hydrogen atom lost may be considered to be lost as H+ + e–. These changes can be represented by the following two equations. H2O  [O] + 2H+ + 2e– [H]  H+ + e– Compound X is oxidised by heating under reflux with hot, acidified potassium dichromate(VI) for one hour. The half-equation for the reduction reaction is shown. Cr2O7 2– + 14H+ + 6e–  2Cr3+ + 7H2O Under these conditions, one mole of potassium dichromate(VI) oxidises three moles of X. What could X be? A propanal B propan-1-ol C propan-1,2-diol D propan-1,3-diol

1 marks

Answer: A

This question in 9701/11 May/June 2021

Q255 · The equation for a redox reaction is shown 9701/12 May/June 2021

9 The equation for a redox reaction is shown. SnCl 2(aq) + 2HgCl 2(aq)  SnCl 4(aq) + Hg2Cl 2(s) Which species is being oxidised in this reaction? A Sn2+ B Cl – C Hg+ D Hg2+

1 marks

Answer: A

This question in 9701/12 May/June 2021

Q256 · Copper dissolves in dilute nitric acid producing a blue solution of Cu(NO3)2, water and… 9701/13 May/June 2021

9 Copper dissolves in dilute nitric acid producing a blue solution of Cu(NO3)2, water and nitrogen(II) oxide as the only products. How many moles of acid react with three moles of copper in the balanced equation? A 2 B 4 C 6 D 8

1 marks

Answer: D

This question in 9701/13 May/June 2021

Q257 · Two reactions are shown 9701/13 May/June 2021

25 Two reactions are shown. Only one product is identified in each reaction. ethanol + acidified Cr2O7 2–  ethanal ethanol + sodium  sodium ethoxide Which statement about these reactions is correct? A The formations of both ethanal and sodium ethoxide are redox reactions. B The formations of both ethanal and sodium ethoxide result in colour changes. C The formation of ethanal is catalysed by potassium dichromate. D The formation of sodium ethoxide is a dehydration reaction.

1 marks

Answer: A

This question in 9701/13 May/June 2021

Q258 · The equation shows the decomposition of three moles of an ion containing chromium in an… 9701/13 May/June 2021

32 The equation shows the decomposition of three moles of an ion containing chromium in an acid solution. 3CrO4 3–(aq) + 8H+(aq)  2CrO4 2–(aq) + Cr3+(aq) + 4H2O(l) Which statements are correct? 1 One mole of CrO4 3– is reduced. 2 Two moles of CrO4 3– are oxidised. 3 Three moles of electrons are transferred.

1 marks

Answer: B

This question in 9701/13 May/June 2021

Q259 · Zinc atoms can be oxidised to Zn2+ ions by dichromate(VI) ions in acid solution 9701/11 Oct/Nov 2021

9 Zinc atoms can be oxidised to Zn2+ ions by dichromate(VI) ions in acid solution. Chromium is reduced to Cr3+ in this reaction. Which equation is correct? A Cr2O7 2– + Zn + 14H+  2Cr3+ + Zn2+ + 7H2O B Cr2O7 2– + Zn + 14H+  2Cr3+ + 3Zn2+ + 7H2O C Cr2O7 2– + 3Zn + 14H+  2Cr3+ + 3Zn2+ + 7H2O D 2Cr2O7 2– + 3Zn + 14H+  2Cr3+ + 3Zn2+ + 7H2O

1 marks

Answer: C

This question in 9701/11 Oct/Nov 2021

Q260 · Z is a compound of sodium, chlorine and oxygen 9701/11 Oct/Nov 2021

17 Z is a compound of sodium, chlorine and oxygen. It contains 45.1% by mass of oxygen. Z is prepared by reacting sodium hydroxide with chlorine. Which row shows the conditions used for the reaction and the oxidation state of chlorine in Z? reaction conditions oxidation state of Cl in Z A cold dilute NaOH +1 B cold dilute NaOH +5 C hot concentrated NaOH +1 D hot concentrated NaOH +5

1 marks

Answer: D

This question in 9701/11 Oct/Nov 2021

Q261 · Which statements about calcium oxide are correct? 9701/11 Oct/Nov 2021

36 Which statements about calcium oxide are correct? 1 It can be reduced by heating with magnesium. 2 It is produced when calcium nitrate is heated. 3 It reacts with cold water.

1 marks

Answer: C

This question in 9701/11 Oct/Nov 2021

Q262 · In a catalytic converter in the exhaust system of a car, carbon monoxide is oxidised to… 9701/12 Oct/Nov 2021

10 In a catalytic converter in the exhaust system of a car, carbon monoxide is oxidised to carbon dioxide, and nitrogen monoxide is reduced to nitrogen. What are the changes in oxidation number of carbon and nitrogen in these two processes? carbon nitrogen A –2 +2 B –1 +1 C +1 –1 D +2 –2

1 marks

Answer: D

This question in 9701/12 Oct/Nov 2021

Q263 · Redox reactions are common in the chemistry of Group 17 elements 9701/12 Oct/Nov 2021

15 Redox reactions are common in the chemistry of Group 17 elements. Which statement is correct? A Br – ions will reduce Cl 2 but not I2. B Cl 2 will oxidise Br – ions but not I– ions. C F2 is the weakest oxidising agent out of F2, Cl 2, Br2 and I2. D I– ions are the weakest reducing agent out of F –, Cl –, Br – and I–.

1 marks

Answer: A

This question in 9701/12 Oct/Nov 2021

Q264 · Which reactions are redox reactions? 9701/12 Oct/Nov 2021

33 Which reactions are redox reactions? 1 Mg + 2HCl  MgCl 2 + H2 2 2K2CrO4 + 2H+  K2Cr2O7 + 2K+ + H2O 3 CuCO3 + 2HCl  CuCl 2 + H2O + CO2

1 marks

Answer: D

This question in 9701/12 Oct/Nov 2021

Q265 · Zinc atoms can be oxidised to Zn2+ ions by dichromate(VI) ions in acid solution 9701/13 Oct/Nov 2021

9 Zinc atoms can be oxidised to Zn2+ ions by dichromate(VI) ions in acid solution. Chromium is reduced to Cr3+ in this reaction. Which equation is correct? A Cr2O7 2– + Zn + 14H+  2Cr3+ + Zn2+ + 7H2O B Cr2O7 2– + Zn + 14H+  2Cr3+ + 3Zn2+ + 7H2O C Cr2O7 2– + 3Zn + 14H+  2Cr3+ + 3Zn2+ + 7H2O D 2Cr2O7 2– + 3Zn + 14H+  2Cr3+ + 3Zn2+ + 7H2O

1 marks

Answer: C

This question in 9701/13 Oct/Nov 2021

Q266 · Z is a compound of sodium, chlorine and oxygen 9701/13 Oct/Nov 2021

17 Z is a compound of sodium, chlorine and oxygen. It contains 45.1% by mass of oxygen. Z is prepared by reacting sodium hydroxide with chlorine. Which row shows the conditions used for the reaction and the oxidation state of chlorine in Z? reaction conditions oxidation state of Cl in Z A cold dilute NaOH +1 B cold dilute NaOH +5 C hot concentrated NaOH +1 D hot concentrated NaOH +5

1 marks

Answer: D

This question in 9701/13 Oct/Nov 2021

Q267 · Which statements about calcium oxide are correct? 9701/13 Oct/Nov 2021

36 Which statements about calcium oxide are correct? 1 It can be reduced by heating with magnesium. 2 It is produced when calcium nitrate is heated. 3 It reacts with cold water.

1 marks

Answer: C

This question in 9701/13 Oct/Nov 2021

Q268 · A student reacts 1 mol of copper with concentrated nitric acid to produce 1 mol of… 9701/11 May/June 2022

4 A student reacts 1 mol of copper with concentrated nitric acid to produce 1 mol of copper(II) nitrate, 2 mol of water and substance X. No other product is formed. Substance X does not contain copper or hydrogen. What could be substance X? A N2 B N2O C NO D NO2

1 marks

Answer: D

This question in 9701/11 May/June 2022

Q269 · A student reacts 4 mol of ammonia with oxygen to produce an oxide of nitrogen and water… 9701/11 May/June 2022

11 A student reacts 4 mol of ammonia with oxygen to produce an oxide of nitrogen and water only. Each nitrogen atom increases its oxidation state by 5 in the reaction. How many moles of oxygen gas react with 4 mol of ammonia in this reaction? A 4 mol B 5 mol C 7 mol D 10 mol

1 marks

Answer: B

This question in 9701/11 May/June 2022

Q270 · In the treatment of domestic water supplies, chlorine is added to water to kill bacteria 9701/11 May/June 2022

12 In the treatment of domestic water supplies, chlorine is added to water to kill bacteria. Some Cl O– ions are formed. What is the change in oxidation number of chlorine when forming the Cl O– ion from aqueous chlorine? A –1 B 0 C +1 D +2

1 marks

Answer: C

This question in 9701/11 May/June 2022

Q271 · Solid sodium iodide reacts with concentrated sulfuric acid to form more than one product… 9701/11 May/June 2022

17 Solid sodium iodide reacts with concentrated sulfuric acid to form more than one product that contains sulfur. What is the lowest oxidation number of sulfur in these products? A –2 B 0 C +4 D +6

1 marks

Answer: A

This question in 9701/11 May/June 2022

Q272 · In a catalytic converter, 5.6 g of carbon monoxide react with an excess of nitrogen… 9701/11 May/June 2022

24 In a catalytic converter, 5.6 g of carbon monoxide react with an excess of nitrogen monoxide. What is produced in this reaction? A 2.4 g of C and 6.0 g of NO2 B 2.4 g of C and 9.2 g of NO2 C 8.8 g of CO2 and 1.4 g of N2 D 8.8 g of CO2 and 2.8 g of N2

1 marks

Answer: D

This question in 9701/11 May/June 2022

Q273 · Carbon monoxide, CO, nitrogen dioxide, NO2, and sulfur dioxide, SO2, are all atmospheric… 9701/11 May/June 2022

29 Carbon monoxide, CO, nitrogen dioxide, NO2, and sulfur dioxide, SO2, are all atmospheric pollutants. Which reaction occurs in the atmosphere? A CO is spontaneously oxidised to CO2. B NO2 is reduced to NO by SO2. C NO2 is reduced to NO by CO. D SO2 is oxidised to SO3 by CO2.

1 marks

Answer: B

This question in 9701/11 May/June 2022

Q274 · NCl 3 reacts with H2O 9701/12 May/June 2022

11 NCl 3 reacts with H2O. NCl 3 + 3H2O  NH3 + 3HCl O The oxidation state of nitrogen does not change in this reaction. Which statement is correct? A Chlorine is reduced. B Chlorine is oxidised. C Hydrogen is both oxidised and reduced. D This is not a redox reaction.

1 marks

Answer: D

This question in 9701/12 May/June 2022

Q275 · In which row do the oxidation numbers of vanadium increase? 9701/12 May/June 2022

12 In which row do the oxidation numbers of vanadium increase? smallest largest A VO4 3– VO3 – VO2 + B VO2+ V2O3 VO4 3– C V2O3 VO2+ VO3 – D VO4 3– VO2 + VO2+

1 marks

Answer: C

This question in 9701/12 May/June 2022

Q276 · Chlorine reacts with aqueous sodium hydroxide forming two chlorine-containing products 9701/12 May/June 2022

23 Chlorine reacts with aqueous sodium hydroxide forming two chlorine-containing products. Which row shows the oxidation states of chlorine in the products under the conditions stated? oxidation state conditions of Cl in products A cold NaOH(aq) –1 and +3 B cold NaOH(aq) –1 and +5 C hot NaOH(aq) –1 and +3 D hot NaOH(aq) –1 and +5

1 marks

Answer: D

This question in 9701/12 May/June 2022

Q277 · A catalytic converter reduces the amount of pollutants in the fumes from a car exhaust 9701/12 May/June 2022

24 A catalytic converter reduces the amount of pollutants in the fumes from a car exhaust. Which row identifies a pollutant and shows how it is removed by the action of the catalyst? pollutant chemical removal A carbon dioxide reduced to carbon B carbon monoxide oxidised to carbon dioxide C oxides of nitrogen oxidised to nitric acid D unburnt hydrocarbons oxidised to carbon dioxide and hydrogen

1 marks

Answer: B

This question in 9701/12 May/June 2022

Q278 · Solid R is added to a solution of ammonium nitrate and the mixture is heated 9701/12 May/June 2022

25 Solid R is added to a solution of ammonium nitrate and the mixture is heated. A gas is given off which turns red litmus to blue. What could be R? A aluminium chloride B magnesium chloride C sodium oxide D phosphorus oxide

1 marks

Answer: C

This question in 9701/12 May/June 2022

Q279 · Which reaction is a redox reaction? 9701/12 May/June 2022

37 Which reaction is a redox reaction? A ethanenitrile heated under reflux with dilute hydrochloric acid B ethanoic acid reacted with aqueous sodium hydroxide C ethanoic acid reacted with sodium D ethyl ethanoate heated under reflux with dilute hydrochloric acid

1 marks

Answer: C

This question in 9701/12 May/June 2022

Q280 · NH4NO3 decomposes into N2O and H2O on heating 9701/13 May/June 2022

11 NH4NO3 decomposes into N2O and H2O on heating. Which statements are correct? 1 The ammonium ion is behaving as a reducing agent. 2 The nitrate(V) ion is behaving as an oxidising agent. 3 It is a redox reaction. 4 It is a disproportionation reaction. A 1, 2, 3 and 4 B 1, 2 and 3 only C 3 and 4 only D 3 only

1 marks

Answer: B

This question in 9701/13 May/June 2022

Q281 · A student adds 3 mol of acidified K2Cr2O7 to an excess of I– ions 9701/13 May/June 2022

12 A student adds 3 mol of acidified K2Cr2O7 to an excess of I– ions. The chromium is all reduced to Cr3+ and I– ions are oxidised to I2. The I2 released is reduced back to I– ions by X mol of S2O3 2– ions. 1 mol of I2 is reduced by 2 mol of S2O3 2– ions. What is the value of X? A 3 B 6 C 9 D 18

1 marks

Answer: D

This question in 9701/13 May/June 2022

Q282 · Ammonium ions are converted into nitrate ions by bacteria 9701/11 Oct/Nov 2022

11 Ammonium ions are converted into nitrate ions by bacteria. What is the change in the oxidation number of nitrogen? A –6 B +6 C +8 D +9

1 marks

Answer: C

This question in 9701/11 Oct/Nov 2022

Q283 · Sodium dichromate(VI), Na2Cr2O7, reacts with hydrogen peroxide, H2O2, producing Cr3+… 9701/11 Oct/Nov 2022

12 Sodium dichromate(VI), Na2Cr2O7, reacts with hydrogen peroxide, H2O2, producing Cr3+ ions, water and oxygen. What is the correctly balanced ionic equation for this reaction? A Cr2O7 2– + 2H+ + H2O2 → 2Cr3+ + 2H2O + 4O2 B Cr2O7 2– + 8H+ + 3H2O2 → 2Cr3+ + 7H2O + 3O2 C Cr2O7 2– + 8H+ + 6H2O2 → 2Cr3+ + 10H2O + 6O2 D Cr2O7 2– + 14H+ + 3H2O2 → 2Cr3+ + 7H2O + 3O2

1 marks

Answer: B

This question in 9701/11 Oct/Nov 2022

Q284 · Which pair of reagents react together in a redox reaction? 9701/11 Oct/Nov 2022

28 Which pair of reagents react together in a redox reaction? A CH3CHCH2 + Br2 B CH3CH2CH2OH + concentrated H3PO4 C CH3COCH3 + HCN D HCO2C2H5 + dilute H2SO4

1 marks

Answer: A

This question in 9701/11 Oct/Nov 2022

Q285 · Two moles of VO2 + ions react with one mole of zinc atoms in the presence of dilute acid 9701/12 Oct/Nov 2022

5 Two moles of VO2 + ions react with one mole of zinc atoms in the presence of dilute acid. The products include Zn2+ ions and an ion, Y. Ion Y contains vanadium. Only zinc and vanadium change oxidation state in the reaction. What is ion Y? A VO3 – B VO+ C VO2+ D VO2 2+

1 marks

Answer: C

This question in 9701/12 Oct/Nov 2022

Q286 · The compound potassium bismuthate(V), KBiO3, is a powerful oxidising agent 9701/12 Oct/Nov 2022

6 The compound potassium bismuthate(V), KBiO3, is a powerful oxidising agent. What is the significance of the (V) in potassium bismuthate(V)? A It is the oxidation number of the bismuth atom. B It is the charge of the bismuthate ion. C It is the oxidation number of the bismuthate ion. D It is the sum of the charges of the two ions present.

1 marks

Answer: A

This question in 9701/12 Oct/Nov 2022

Q287 · What is the oxidation state of the chlorine-containing species that kills bacteria in… 9701/12 Oct/Nov 2022

21 What is the oxidation state of the chlorine-containing species that kills bacteria in drinking water? A –1 B +1 C +3 D +5

1 marks

Answer: B

This question in 9701/12 Oct/Nov 2022

Q288 · Ammonium ions are converted into nitrate ions by bacteria 9701/13 Oct/Nov 2022

11 Ammonium ions are converted into nitrate ions by bacteria. What is the change in the oxidation number of nitrogen? A –6 B +6 C +8 D +9

1 marks

Answer: C

This question in 9701/13 Oct/Nov 2022

Q289 · Sodium dichromate(VI), Na2Cr2O7, reacts with hydrogen peroxide, H2O2, producing Cr3+… 9701/13 Oct/Nov 2022

12 Sodium dichromate(VI), Na2Cr2O7, reacts with hydrogen peroxide, H2O2, producing Cr3+ ions, water and oxygen. What is the correctly balanced ionic equation for this reaction? A Cr2O7 2– + 2H+ + H2O2  2Cr3+ + 2H2O + 4O2 B Cr2O7 2– + 8H+ + 3H2O2  2Cr3+ + 7H2O + 3O2 C Cr2O7 2– + 8H+ + 6H2O2  2Cr3+ + 10H2O + 6O2 D Cr2O7 2– + 14H+ + 3H2O2  2Cr3+ + 7H2O + 3O2

1 marks

Answer: B

This question in 9701/13 Oct/Nov 2022

Q290 · Which pair of reagents react together in a redox reaction? 9701/13 Oct/Nov 2022

28 Which pair of reagents react together in a redox reaction? A CH3CHCH2 + Br2 B CH3CH2CH2OH + concentrated H3PO4 C CH3COCH3 + HCN D HCO2C2H5 + dilute H2SO4

1 marks

Answer: A

This question in 9701/13 Oct/Nov 2022

Q291 · Four equations representing reactions of nitrogen or one of its compounds are given 9701/12 Feb/March 2023

1 Four equations representing reactions of nitrogen or one of its compounds are given. Which equation represents a disproportionation reaction? A 2HNO3 + CaCO3 →Ca(NO3)2 + CO2 + H2O B N2 + 3H2 →2NH3 C NH4Cl + NaOH →NH3 + NaCl + H2O D 2NO2 + H2O →HNO3 + HNO2

1 marks

Answer: D

This question in 9701/12 Feb/March 2023

Q292 · The ore psilomelane may be considered to have the general formula Ba(Mnx+)(Mny+)8O16(OH)4 9701/12 Feb/March 2023

6 The ore psilomelane may be considered to have the general formula Ba(Mnx+)(Mny+)8O16(OH)4. In this general formula, x+ and y+ are the two different oxidation states of manganese in psilomelane. What could be the values of x and y? x y A 2 4 B 6 4 C 6 3 D 7 3

1 marks

Answer: A

This question in 9701/12 Feb/March 2023

Q293 · Silicon reacts with a mixture of calcium oxide and magnesium oxide at 1200 °C 9701/12 Feb/March 2023

7 Silicon reacts with a mixture of calcium oxide and magnesium oxide at 1200 °C. 2MgO + 2CaO + Si →2Mg + Ca2SiO4 Which statement about this reaction is correct? A Calcium is reduced and silicon is neither oxidised nor reduced. B Magnesium is reduced and calcium is neither oxidised nor reduced. C Magnesium is reduced and silicon is neither oxidised nor reduced. D Silicon is reduced and calcium is neither oxidised nor reduced.

1 marks

Answer: B

This question in 9701/12 Feb/March 2023

Q294 · Exhaust gases from an internal combustion engine are made less harmful by passing them… 9701/12 Feb/March 2023

30 Exhaust gases from an internal combustion engine are made less harmful by passing them through a catalytic converter. A number of reactions take place in the catalytic converter. Two such reactions are described in the table. Which row is correct? the type of reaction that the type of reaction that removes unburned removes carbon monoxide hydrocarbons A oxidation oxidation B oxidation reduction C reduction reduction D reduction oxidation

1 marks

Answer: A

This question in 9701/12 Feb/March 2023

Q295 · The ionic equation shows iodide ions reacting with manganate(VII) ions in acidic solution 9701/13 May/June 2023

2 The ionic equation shows iodide ions reacting with manganate(VII) ions in acidic solution. – + vH+ + wI – →xMn2+ + yH2O + zI2 uMnO4 The letters u, v, w, x, y and z all represent whole numbers. Two or more of u, v, w, x, y and z are the same as each other. What is the lowest possible value of v? A 2 B 8 C 10 D 16

1 marks

Answer: D

This question in 9701/13 May/June 2023

Q296 · Electronegativity differences can be used to help determine the oxidation number of an… 9701/13 May/June 2023

6 Electronegativity differences can be used to help determine the oxidation number of an atom in different species. A number of rules are used which include: e The more electronegative atom is given a negative oxidation number. e — Hydrogen is more electronegative than Group 1 metals. e Oxygen is more electronegative than hydrogen. Which row is correct? equation of reaction redox reaction disproportionation reaction A | 2CrO0,* + 2H* > Cr,0,7 + H,O V x B NaH + H,O — NaOH + H, Jv Jv Cc 3Mn0,~ + 4H" — MnO, + 2MnO, Jv Jv D VO, + 2H’ > VO, + H,O J x

1 marks

Answer: C

This question in 9701/13 May/June 2023

Q297 · Which particle contains nitrogen in the same oxidation state as in the ion N2O2 2–? 9701/13 May/June 2023

14 Which particle contains nitrogen in the same oxidation state as in the ion N2O2 2–? A NH2F B N2O4 C NO3 – D HNF2

1 marks

Answer: D

This question in 9701/13 May/June 2023

Q298 · HOCl(aq) is the molecule that kills bacteria when chlorine is added to water 9701/11 Oct/Nov 2023

11 HOCl(aq) is the molecule that kills bacteria when chlorine is added to water. The following reaction produces this molecule. Cl 2(g) + H2O(I) ⇋HOCl(aq) + H+(aq) + Cl –(aq) Which statement about this reaction is correct? A Chlorine is both oxidised and reduced. B Chlorine is oxidised but not reduced. C Hydrogen is both oxidised and reduced. D Hydrogen is oxidised but not reduced.

1 marks

Answer: A

This question in 9701/11 Oct/Nov 2023

Q299 · Which row correctly describes the separate reactions of calcium and strontium with water? 9701/11 Oct/Nov 2023

19 Which row correctly describes the separate reactions of calcium and strontium with water? substance reduced substance oxidised more vigorous reaction A calcium or strontium water calcium + water B calcium or strontium water strontium + water C water calcium or strontium calcium + water D water calcium or strontium strontium + water

1 marks

Answer: D

This question in 9701/11 Oct/Nov 2023

Q300 · Zinc reacts with concentrated nitric acid giving three products only: zinc nitrate, an… 9701/12 Oct/Nov 2023

3 Zinc reacts with concentrated nitric acid giving three products only: zinc nitrate, an oxide of nitrogen and water. 3.0 moles of zinc react with 8.0 moles of nitric acid. Zinc nitrate contains Zn2+ ions. What could be the formula of the oxide of nitrogen? A N2O B NO C N2O3 D NO2 A 3.7g sample of copper(II) carbonate is added to 25cm3 of 2.0moldm–3 hydrochloric acid.

1 marks

Answer: B

This question in 9701/12 Oct/Nov 2023

Q301 · Chlorine reacts with sodium bromide 9701/12 Oct/Nov 2023

12 Chlorine reacts with sodium bromide. Cl 2 + NaBr →NaCl + Br2 Which words correctly describe this reaction? 1 redox 2 displacement 3 disproportionation A 1, 2 and 3 B 1 and 2 only C 1 only D 2 only

1 marks

Answer: B

This question in 9701/12 Oct/Nov 2023

Q302 · The equation for the reaction between aqueous copper ions and aqueous iodide ions is as… 9701/12 Oct/Nov 2023

13 The equation for the reaction between aqueous copper ions and aqueous iodide ions is as follows. 2Cu2+(aq) + 4I–(aq) →2CuI(s) + I2(aq) What is the change in oxidation state of copper? A +2 to –1 B +2 to 0 C +2 to +1 D +4 to +2

1 marks

Answer: C

This question in 9701/12 Oct/Nov 2023

Q303 · Q is a mixture of two compounds of Group 2 elements 9701/12 Oct/Nov 2023

23 Q is a mixture of two compounds of Group 2 elements. Q undergoes thermal decomposition to produce a white solid and only two gaseous products. One of the gaseous products relights a glowing splint. What could be the components of mixture Q? A MgCl 2 and CaCO3 B MgCO3 and Ca(NO3)2 C Mg(NO3)2 and Ca(NO3)2 D MgO and CaO

1 marks

Answer: C

This question in 9701/12 Oct/Nov 2023

Q304 · When concentrated sulfuric acid is added to solid sodium chloride, HCl is formed but not… 9701/12 Oct/Nov 2023

25 When concentrated sulfuric acid is added to solid sodium chloride, HCl is formed but not Cl 2. When concentrated sulfuric acid is added to solid sodium iodide, I2 is formed. Which statement explains these observations? A Sulfuric acid is an oxidising agent and chloride ions are more easily oxidised than iodide ions. B Sulfuric acid is an oxidising agent and iodide ions are more easily oxidised than chloride ions. C Sulfuric acid is a reducing agent and chloride ions are more easily reduced than iodide ions. D Sulfuric acid is a reducing agent and iodide ions are more easily reduced than chloride ions.

1 marks

Answer: B

This question in 9701/12 Oct/Nov 2023

Q305 · HOCl(aq) is the molecule that kills bacteria when chlorine is added to water 9701/13 Oct/Nov 2023

11 HOCl(aq) is the molecule that kills bacteria when chlorine is added to water. The following reaction produces this molecule. Cl 2(g) + H2O(I) ⇋HOCl(aq) + H+(aq) + Cl –(aq) Which statement about this reaction is correct? A Chlorine is both oxidised and reduced. B Chlorine is oxidised but not reduced. C Hydrogen is both oxidised and reduced. D Hydrogen is oxidised but not reduced.

1 marks

Answer: A

This question in 9701/13 Oct/Nov 2023

Q306 · Which row correctly describes the separate reactions of calcium and strontium with water? 9701/13 Oct/Nov 2023

19 Which row correctly describes the separate reactions of calcium and strontium with water? substance reduced substance oxidised more vigorous reaction A calcium or strontium water calcium + water B calcium or strontium water strontium + water C water calcium or strontium calcium + water D water calcium or strontium strontium + water

1 marks

Answer: D

This question in 9701/13 Oct/Nov 2023

Q307 · One of the reactions in the rechargeable lead / acid battery is shown 9701/12 Feb/March 2024

11 One of the reactions in the rechargeable lead / acid battery is shown. Pb(s) + PbO2(s) + 4H+(aq) + 2SO4 2–(aq)  2PbSO4(s) + 2H2O(l) Which statement about this reaction is correct? A Lead is both oxidised and reduced. B Lead is neither oxidised nor reduced. C Lead is oxidised only. D Lead is reduced only.

1 marks

Answer: A

This question in 9701/12 Feb/March 2024

Q308 · KMnO4 is an oxidising agent 9701/12 Feb/March 2024

12 KMnO4 is an oxidising agent. Its reaction with Fe2+ is shown in the following ionic equation. ...X...MnO4 – + … Fe2+ + … H+  … Mn2+ + ...Y...Fe3+ + … H2O What are X and Y when the equation is balanced? X Y A 1 1 B 1 3 C 1 5 D 5 1

1 marks

Answer: C

This question in 9701/12 Feb/March 2024

Q309 · The equations for three reactions involving chlorine or its compounds are listed 9701/12 Feb/March 2024

23 The equations for three reactions involving chlorine or its compounds are listed. 1 2KCl O3  2KCl + 3O2 2 4KCl O3  3KCl O4 + KCl 3 6KOH + 3Cl 2  3H2O + 5KCl + KCl O3 Which statement about these equations is correct? A Equation 1 describes the formation of a compound used to kill bacteria in drinking water. B Equation 1 does not represent a redox reaction. C Equation 2 describes the formation of potassium chlorate(IV). D Equations 2 and 3 both represent disproportionation reactions.

1 marks

Answer: D

This question in 9701/12 Feb/March 2024

Q310 · Nitrogen monoxide, NO, is a primary pollutant produced by petrol engines and is found in… 9701/12 Feb/March 2024

24 Nitrogen monoxide, NO, is a primary pollutant produced by petrol engines and is found in their exhaust gases. Which reaction occurs in a catalytic converter and decreases the emission of nitrogen monoxide? A NO(g) + CO(g)  NO2(g) + C(s) B NO(g) + CO2(g)  NO2(g) + CO(g) C 2NO(g) + 2CO(g)  N2(g) + 2CO2(g) D 2NO(g) + CO2(g)  2NO2(g) + C(s)

1 marks

Answer: C

This question in 9701/12 Feb/March 2024

Q311 · Sodium chromate(VI), Na2CrO4, is manufactured by heating chromite, FeCr2O4, with sodium… 9701/11 May/June 2024

11 Sodium chromate(VI), Na2CrO4, is manufactured by heating chromite, FeCr2O4, with sodium carbonate in an oxidising atmosphere. Chromite contains Cr2O4 2– ions. 2FeCr2O4 + 4Na2CO3 + 3 2 1 O2  4Na2CrO4 + Fe2O3 + 4CO2 What happens in this reaction? A Chromium and iron are the only elements oxidised. B Chromium, iron and carbon are oxidised. C Only chromium is oxidised. D Only iron is oxidised.

1 marks

Answer: A

This question in 9701/11 May/June 2024

Q312 · Oxygen can be prepared by the reaction of potassium manganate(VII), KMnO4, hydrogen… 9701/11 May/June 2024

12 Oxygen can be prepared by the reaction of potassium manganate(VII), KMnO4, hydrogen peroxide, H2O2, and sulfuric acid, H2SO4. Each H2O2 molecule loses two electrons in this reaction. The other products of the reaction are potassium sulfate, manganese(II) sulfate and water. How many moles of oxygen gas are produced when 1.0 mol of KMnO4 reacts with an excess of H2O2 in acidic conditions? A 2.0 mol B 2.5 mol C 4.5 mol D 5.0 mol

1 marks

Answer: B

This question in 9701/11 May/June 2024

Q313 · A solid sodium halide, NaX, is reacted with concentrated sulfuric acid 9701/11 May/June 2024

21 A solid sodium halide, NaX, is reacted with concentrated sulfuric acid. The lowest oxidation state of sulfur in the products is +4. Halogen Y2 is less volatile than halogen X2. What are the identities of sodium halide NaX and halogen Y2? sodium halide NaX halogen Y2 A sodium bromide chlorine B sodium bromide iodine C sodium iodide bromine D sodium iodide astatine

1 marks

Answer: B

This question in 9701/11 May/June 2024

Q314 · In which pairs are both species free radicals? 9701/12 May/June 2024

4 In which pairs are both species free radicals? 1 Cl and O 2 Cl – and O2– 3 Cl and O– 4 Cl + and O2+ A 1, 3 and 4 B 1 and 3 only C 1 only D 2 only

1 marks

Answer: A

This question in 9701/12 May/June 2024

Q315 · Nitrogen dioxide reacts with water 9701/12 May/June 2024

11 Nitrogen dioxide reacts with water. 2NO2 + H2O  HNO2 + HNO3 Which statement about this reaction is correct? A Both products are formed because oxygen atoms gain electrons. B Nitrogen atoms undergo disproportionation. C The oxidation number of hydrogen is increased. D Water acts as an oxidising agent.

1 marks

Answer: B

This question in 9701/12 May/June 2024

Q316 · Phosphorus reacts with concentrated sulfuric acid to produce phosphoric acid, sulfur… 9701/12 May/June 2024

12 Phosphorus reacts with concentrated sulfuric acid to produce phosphoric acid, sulfur dioxide and water. aH2SO4 + bP  cH3PO4 + dSO2 + eH2O a, b, c, d and e are all whole numbers. The equation can be balanced by using oxidation numbers. What is the value of the sum a + b + c + d + e? A 10 B 14 C 15 D 16

1 marks

Answer: D

This question in 9701/12 May/June 2024

Q317 · Chlorine gas is reacted with cold aqueous sodium hydroxide 9701/12 May/June 2024

19 Chlorine gas is reacted with cold aqueous sodium hydroxide. Which statement is correct for this reaction? A Chlorine is both oxidised and reduced. B Chlorine is neither oxidised nor reduced. C Chlorine is oxidised but not reduced. D Chlorine is reduced but not oxidised.

1 marks

Answer: A

This question in 9701/12 May/June 2024

Q318 · In which reaction does the oxidation number of chlorine change by the largest amount? 9701/13 May/June 2024

11 In which reaction does the oxidation number of chlorine change by the largest amount? A 2KCl O3  2KCl + 3O2 B 2Cl O–  Cl – + Cl O2 – C Cl 2 + H2O  HCl + HCl O D 2NaCl O2 + Cl 2  2NaCl + 2Cl O2

1 marks

Answer: A

This question in 9701/13 May/June 2024

Q319 · W moles of HNO2 undergoes a disproportionation reaction to produce U moles of HNO3 and V… 9701/13 May/June 2024

13 W moles of HNO2 undergoes a disproportionation reaction to produce U moles of HNO3 and V moles of NO. ● No other nitrogen containing product is produced. ● Nitrogen is the only element oxidised or reduced. What are the values of W, U and V? W U V A 2 1 1 B 3 1 2 C 5 3 2 D 5 1 4

1 marks

Answer: B

This question in 9701/13 May/June 2024

Q320 · ICl is made when Cl 2 and I2 react together 9701/13 May/June 2024

22 ICl is made when Cl 2 and I2 react together. Cl 2 + I2 2ICl ICl reacts with water. 5ICl + 3H2O  5HCl + HIO3 + 2I2 Which row is correct? oxidation number reaction occurring of I in ICl when ICl reacts with H2O A +1 the iodine atoms are oxidised to form I2 B +1 the iodine atoms are oxidised to form HIO3 C –1 the chlorine atoms are reduced to form HCl D –1 the iodine atoms are oxidised to form HIO3

1 marks

Answer: B

This question in 9701/13 May/June 2024

Q321 · In alkaline solution, MnO4 – ions oxidise SO3 2– ions to SO4 2– ions 9701/11 Oct/Nov 2024

11 In alkaline solution, MnO4 – ions oxidise SO3 2– ions to SO4 2– ions. The MnO4 – ions are reduced to MnO2. What is the ratio of the two ions in the balanced chemical equation for this reaction? MnO4 – SO3 2– A 2 3 B 3 2 C 4 7 D 7 4

1 marks

Answer: A

This question in 9701/11 Oct/Nov 2024

Q322 · Which species contains a different number of electrons from the other three? 9701/12 Oct/Nov 2024

1 Which species contains a different number of electrons from the other three? A Cl O4 – B H2SO4 C SO4 2– D Te2–

1 marks

Answer: D

This question in 9701/12 Oct/Nov 2024

Q323 · Equations for some reactions of hydrogen peroxide are given 9701/12 Oct/Nov 2024

11 Equations for some reactions of hydrogen peroxide are given. 1 2Fe2+ + H2O2 + 2H+  2Fe3+ + 2H2O 2 2MnO4 – + 5H2O2 + 6H+  2Mn2+ + 8H2O + 5O2 3 2Fe3+ + H2O2 + 2OH–  2Fe2+ + O2 + 2H2O In which reactions is hydrogen peroxide acting as a reducing agent? A 1 and 3 B 1 only C 2 and 3 D 2 only

1 marks

Answer: C

This question in 9701/12 Oct/Nov 2024

Q324 · The equation for the reaction of aqueous thiosulfate ions, S2O3 2–, and aqueous… 9701/12 Oct/Nov 2024

12 The equation for the reaction of aqueous thiosulfate ions, S2O3 2–, and aqueous dioxo-vanadium ions, VO2 +, is shown. 2S2O3 2– + xVO2 + + yH+  S4O6 2– + zVO2+ + 2H2O Which row shows two correct statements about the equation for this reaction? change in oxidation comparison of x and y to z number of vanadium A x and z are the same value from +4 to +5 and quarter the value of y B x and z are the same value from +5 to +4 and quarter the value of y C x and z are the same value from +5 to +4 and half the value of y D x and z are the same value from +4 to +5 and half the value of y

1 marks

Answer: C

This question in 9701/12 Oct/Nov 2024

Q325 · The name ‘chlorate’ is used for an anion consisting of chlorine and oxygen only 9701/12 Oct/Nov 2024

23 The name ‘chlorate’ is used for an anion consisting of chlorine and oxygen only. In a molecule of ICl, the iodine atom has oxidation number x and the chlorine atom has oxidation number y. When ICl is added to H2O, iodine is reduced. 4ICl + 2H2O  4HCl + O2 + 2I2 Which statement about the value of x or y is correct? A x is the same as the oxidation number of Cl in the chlorate ion formed when Cl 2(aq) is added to cold NaOH(aq). B x is the same as the oxidation number of Cl in the chlorate ion formed when Cl 2(aq) is added to hot NaOH(aq). C y is the same as the oxidation number of Cl in the chlorate ion formed when Cl 2(aq) is added to cold NaOH(aq). D y is the same as the oxidation number of Cl in the chlorate ion formed when Cl 2(aq) is added to hot NaOH(aq).

1 marks

Answer: A

This question in 9701/12 Oct/Nov 2024

Q326 · In alkaline solution, MnO4 – ions oxidise SO3 2– ions to SO4 2– ions 9701/13 Oct/Nov 2024

11 In alkaline solution, MnO4 – ions oxidise SO3 2– ions to SO4 2– ions. The MnO4 – ions are reduced to MnO2. What is the ratio of the two ions in the balanced chemical equation for this reaction? MnO4 – SO3 2– A 2 3 B 3 2 C 4 7 D 7 4

1 marks

Answer: A

This question in 9701/13 Oct/Nov 2024

Q327 · The equation for a reaction of KCl O3 is shown 9701/12 Feb/March 2025

11 The equation for a reaction of KCl O3 is shown. 4KCl O3  KCl + 3KCl O4 Which row is correct? disproportionation oxidation number reaction of chlorine in KCl O4 A yes +4 B yes +7 C no +4 D no +7

1 marks

Answer: B

This question in 9701/12 Feb/March 2025

Q328 · Copper reacts with nitric acid under certain conditions 9701/12 Feb/March 2025

14 Copper reacts with nitric acid under certain conditions. The products are copper(II) nitrate, water and an oxide of nitrogen. 3 mol of copper reacts with exactly 8 mol of nitric acid. What is the oxidation state of nitrogen in the oxide produced? A +1 B +2 C +3 D +4

1 marks

Answer: B

This question in 9701/12 Feb/March 2025

Q329 · U, V and W represent different halogens 9701/12 Feb/March 2025

19 U, V and W represent different halogens. The table shows the results of nine experiments in which aqueous solutions of U2, V2 and W2 were separately added to separate aqueous solutions containing U–, V – and W – ions. U–(aq) V –(aq) W –(aq) U2(aq) no reaction no reaction no reaction V2(aq) U2 formed no reaction W2 formed W2(aq) U2 formed no reaction no reaction Which row contains the ions U–, V – and W – in order of their decreasing strength as reducing agents? strongest weakest A U– V – W – B U– W – V – C V – W – U– D W – U– V –

1 marks

Answer: B

This question in 9701/12 Feb/March 2025

Q330 · Two nitrates decompose on heating according to the equations shown 9701/12 Feb/March 2025

25 Two nitrates decompose on heating according to the equations shown. 2Pb(NO3)2(s)  2PbO(s) + 4NO2(g) + O2(g) 2NH4NO3(s)  2N2(g) + O2(g) + 4H2O(l) One mole of each nitrate is heated separately. The gas produced in each reaction is bubbled through NaOH(aq). The volume of any gas that does not react with NaOH(aq) is then collected and measured. Which nitrate: ● shows the greater percentage loss in mass ● produces the greater volume of gas collected? greater percentage greater volume loss of mass of gas collected A NH4NO3 NH4NO3 B NH4NO3 Pb(NO3)2 C Pb(NO3)2 NH4NO3 D Pb(NO3)2 Pb(NO3)2

1 marks

Answer: A

This question in 9701/12 Feb/March 2025

Q331 · ICl3 reacts with water in a redox reaction 9701/11 May/June 2025

1 ICl3 reacts with water in a redox reaction. vICl3 + wH2O xHCl + yHI + zHIO3 + zHClO3 What are the numbers v, x and z in the correctly balanced equation? v x z A 2 8 1 B 2 5 1 C 3 8 1 D 3 5 1

1 marks

Mark scheme: Question Answer Marks 1 C 1

This question in 9701/11 May/June 2025

Q332 · A reaction involving ammonium ions is shown 9701/11 May/June 2025

16 A reaction involving ammonium ions is shown. NH4 + + OH– NH3 + H2O Four statements about this reaction are listed. 1 The ammonium ions are reduced. 2 In the reverse reaction, ammonia acts as a Brønsted–Lowry base. 3 The ammonium ion and the ammonia molecule have the same bond angle. 4 This reaction is not a redox reaction. Which statements are correct? A 1 and 2 B 1 and 3 C 2 and 4 D 3 and 4

1 marks

Answer: C

This question in 9701/11 May/June 2025

Q333 · Which reagent or reagents and conditions will oxidise chlorine, Cl2, into a compound… 9701/11 May/June 2025

19 Which reagent or reagents and conditions will oxidise chlorine, Cl2, into a compound containing chlorine in the +5 oxidation state? A AgNO3(aq) followed by NH3(aq) at room temperature B concentrated H2SO4 at room temperature C cold dilute NaOH(aq) D hot concentrated NaOH(aq)

1 marks

Answer: D

This question in 9701/11 May/June 2025

Q334 · ‘Red lead’ is a red pigment with the formula Pb3O4 9701/12 May/June 2025

5 ‘Red lead’ is a red pigment with the formula Pb3O4. Every formula unit of ‘red lead’ is the same. Each formula unit contains three lead ions and four oxide ions. Lead has two different oxidation states in ‘red lead’. What are the oxidation states of lead in ‘red lead’? A +1 and +2 B +1 and +3 C +2 and +4 D +2 and +6

1 marks

Answer: C

This question in 9701/12 May/June 2025

Q335 · Sodium bromide is warmed with concentrated sulfuric acid 9701/12 May/June 2025

20 Sodium bromide is warmed with concentrated sulfuric acid. Which row describes the change in the oxidation number of the sulfur and the role of the bromide ions in the reaction? change in role of oxidation number bromide ions of sulfur A +6 to +4 oxidising agent B +6 to +4 reducing agent C +4 to 0 oxidising agent D +4 to 0 reducing agent

1 marks

Answer: B

This question in 9701/12 May/June 2025

Q336 · Chromium is present in compound X 9701/13 May/June 2025

4 Chromium is present in compound X. ● Two moles of compound X react with exactly 3 moles of silicon. ● The only products of this reaction are 4 moles of chromium and 3 moles of a silicon compound in which the oxidation state of the silicon is +4. ● Chromium and silicon are the only elements that change their oxidation states in this reaction. What could be the identity of compound X? A Cr2O3 B Cr2H6 C Cr2H4 D Cr2O4

1 marks

Answer: A

This question in 9701/13 May/June 2025

Q337 · In this question, the average oxidation state of sulfur in S2O3 2– and sulfur in S2O4 2… 9701/14 May/June 2025

6 In this question, the average oxidation state of sulfur in S2O3 2– and sulfur in S2O4 2– should be used. In which reaction does the underlined element have the largest increase in oxidation state? A 3CrO4 3–(aq) + 8H+(aq)  2CrO4 2–(aq) + Cr3+(aq) + 4H2O(l) B 2NO2(g) + H2O(l)  HNO3(aq) + HNO2(aq) C S2O3 2–(aq) + 2H+(aq)  S(s) + SO2(g) + H2O(l) D 2S2O4 2–(aq) + H2O(l)  S2O3 2–(aq) + 2HSO3 –(aq)

1 marks

Answer: C

This question in 9701/14 May/June 2025

Q338 · When K2MnO4 reacts with concentrated hydrochloric acid, the products include chlorine… 9701/14 May/June 2025

14 When K2MnO4 reacts with concentrated hydrochloric acid, the products include chlorine molecules and MnCl 2. All of the manganese atoms are reduced to MnCl 2. Both Mn and Cl change their oxidation numbers during the reaction. No other element is oxidised or reduced. Using these changes in oxidation number, how many moles of chlorine will be produced when 1.0 mol of K2MnO4 reacts with an excess of hydrochloric acid? A 2.0 mol B 2.5 mol C 3.0 mol D 4.0 mol

1 marks

Answer: A

This question in 9701/14 May/June 2025

Q339 · Sulfite ions, SO3 2–, react separately with zinc and with manganese dioxide 9701/11 Oct/Nov 2025

9 Sulfite ions, SO3 2–, react separately with zinc and with manganese dioxide. a, b, c, d, w, x, y and z are all whole numbers. aSO3 2–(aq) + bH2O(l) + Zn(s)  Zn2+(aq) + cOH–(aq) + dS2O4 2–(aq) MnO2(s) + wSO3 2–(aq) + xH+(aq)  Mn2+(aq) + yS2O6 2–(aq) + zH2O(l) Which numbers are correct for a, b, w and x? a b w x A 1 2 2 4 B 2 2 2 4 C 1 2 4 2 D 2 2 4 2

1 marks

Answer: B

This question in 9701/11 Oct/Nov 2025

Q340 · Which equation shows hydrogen acting as an oxidising agent? 9701/11 Oct/Nov 2025

10 Which equation shows hydrogen acting as an oxidising agent? A H2 + 2K  2K+H– B H2 + I2 2HI C H2 + Cu2S + ZnO  2Cu + ZnS + H2O D 3H2 + N2 2NH3

1 marks

Answer: A

This question in 9701/11 Oct/Nov 2025

Q341 · Photochromic glass, used for sunglasses, darkens when exposed to bright light and becomes… 9701/11 Oct/Nov 2025

14 Photochromic glass, used for sunglasses, darkens when exposed to bright light and becomes more transparent again when the light is less bright. The darkness of the glass is due to the presence of silver atoms. The following reactions are involved. reaction 1 Ag+ + Cl– Ag + Cl reaction 2 Cu+ + Cl Cu2+ + Cl– reaction 3 Cu2+ + Ag  Cu+ + Ag+ Which statement about these reactions is correct? A Cu+ and Cu2+ ions act as catalysts. B Cu+ ions act as an oxidising agent in reaction 2. C Reaction 3 increases the darkness of the glass. D Silver atoms are reduced in reaction 3.

1 marks

Answer: A

This question in 9701/11 Oct/Nov 2025

Q342 · What happens when iodine solution is added to a solution of sodium bromide? 9701/11 Oct/Nov 2025

22 What happens when iodine solution is added to a solution of sodium bromide? A A reaction occurs without changes in oxidation state. B Bromide ions are oxidised; iodine atoms are reduced. C Bromide ions are reduced; iodine atoms are oxidised. D No reaction occurs.

1 marks

Answer: D

This question in 9701/11 Oct/Nov 2025

Q343 · The reaction of hydrogen sulfide with sulfur dioxide gives sulfur as one of the products 9701/12 Oct/Nov 2025

3 The reaction of hydrogen sulfide with sulfur dioxide gives sulfur as one of the products. The two relevant redox equations are shown. H2S(aq) S(s) + 2H+(aq) + 2e– SO2(aq) + 4H+(aq) + 4e– S(s) + 2H2O(l) How many moles of hydrogen sulfide are needed to react with sulfur dioxide to produce 1 mol of sulfur? 1 mol 2 mol C 3 mol A B D 2 mol 3 3 2

1 marks

Answer: B

This question in 9701/12 Oct/Nov 2025

Q344 · One commercially available ‘heat pad’ contains iron, activated carbon and water 9701/12 Oct/Nov 2025

10 One commercially available ‘heat pad’ contains iron, activated carbon and water. The ‘heat pad’ is activated by air. This causes the pad to get hotter. Which statement describes the chemical reaction occurring in the ‘heat pad’ when it is exposed to air? A The reaction is endothermic and iron gains electrons. B The reaction is endothermic and iron loses electrons. C The reaction is exothermic and iron gains electrons. D The reaction is exothermic and iron loses electrons.

1 marks

Answer: D

This question in 9701/12 Oct/Nov 2025

Q345 · In which substance is the average oxidation number of sulfur the highest? 9701/12 Oct/Nov 2025

11 In which substance is the average oxidation number of sulfur the highest? A S8 B Na2S4O6 C Na2S2O3 D SO2Cl 2

1 marks

Answer: D

This question in 9701/12 Oct/Nov 2025

Q346 · In an experiment, 0.600 mol of chlorine gas, Cl 2, is reacted with an excess of hot… 9701/12 Oct/Nov 2025

21 In an experiment, 0.600 mol of chlorine gas, Cl 2, is reacted with an excess of hot aqueous sodium hydroxide. One of the products is NaCl O3. Which mass of NaCl O3 is formed? A 21.3 g B 44.7 g C 63.9 g D 128 g

1 marks

Answer: A

This question in 9701/12 Oct/Nov 2025

Q347 · Sulfite ions, SO3 2–, react separately with zinc and with manganese dioxide 9701/13 Oct/Nov 2025

9 Sulfite ions, SO3 2–, react separately with zinc and with manganese dioxide. a, b, c, d, w, x, y and z are all whole numbers. aSO3 2–(aq) + bH2O(l) + Zn(s)  Zn2+(aq) + cOH–(aq) + dS2O4 2–(aq) MnO2(s) + wSO3 2–(aq) + xH+(aq)  Mn2+(aq) + yS2O6 2–(aq) + zH2O(l) Which numbers are correct for a, b, w and x? a b w x A 1 2 2 4 B 2 2 2 4 C 1 2 4 2 D 2 2 4 2

1 marks

Answer: B

This question in 9701/13 Oct/Nov 2025

Q348 · Which equation shows hydrogen acting as an oxidising agent? 9701/13 Oct/Nov 2025

10 Which equation shows hydrogen acting as an oxidising agent? A H2 + 2K  2K+H– B H2 + I2 2HI C H2 + Cu2S + ZnO  2Cu + ZnS + H2O D 3H2 + N2 2NH3

1 marks

Answer: A

This question in 9701/13 Oct/Nov 2025

Q349 · What happens when iodine solution is added to a solution of sodium bromide? 9701/13 Oct/Nov 2025

22 What happens when iodine solution is added to a solution of sodium bromide? A A reaction occurs without changes in oxidation state. B Bromide ions are oxidised; iodine atoms are reduced. C Bromide ions are reduced; iodine atoms are oxidised. D No reaction occurs.

1 marks

Answer: D

This question in 9701/13 Oct/Nov 2025