Cambridge IGCSE Chemistry (9-1) 0971 — 2023 May/June Paper 3 · Variant 2

1 Fig. 1.1 shows part of the Periodic Table. I II III IV V VI VII VIII He C N O Ne Cl K Ca Cr Cu Zn Br Sr I Fig. 1.1 Answer the following questions using only the elements in Fig. 1.1. Each symbol of the element may be used once, more than once or not at all. Give the symbol of the element that: (a) forms 21% by volume of clean, dry air .............................................................................................................................................. [1] (b) has an atom with only three occupied electron shells .............................................................................................................................................. [1] (c) has an atom with only one electron in its outer shell .............................................................................................................................................. [1] (d) is a grey-black solid at room temperature .............................................................................................................................................. [1] (e) forms an ion that gives a green precipitate on addition of aqueous ammonia .............................................................................................................................................. [1] (f) is used in electrical wiring because of its good ductility. .............................................................................................................................................. [1] [Total: 6]

Mark scheme: 1(a) O 1 1(b) Cl 1 1(c) K 1 1(d) I 1 1(e) Cr 1 1(f) Cu 1

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2 (a) Table 2.1 shows some properties of the halogens. Table 2.1 density at room melting point boiling point halogen temperature and in °C in °C pressure in g / cm3 chlorine –101 –35 0.003 bromine –7 +59 3.12 iodine +114 4.93 astatine +302 +337 Use the information in Table 2.1 to predict: (i) the boiling point of iodine ���������������������������������������������������������������������������������������������� [1] (ii) the density of astatine at room temperature and pressure ������������������������������������������� [1] (iii) the physical state of bromine at +50 °C. Give a reason for your answer. physical state ...................................................................................................................... reason ................................................................................................................................. ............................................................................................................................................. [2] (b) Aqueous bromine reacts with aqueous potassium iodide. (i) Complete the word equation for this reaction. potassium ........................ bromine + → ........................ + iodide ........................ [2] (ii) Explain why aqueous iodine does not react with aqueous potassium bromide. ....................................................................................................................................... [1] (iii) Describe a test for iodide ions. test ...................................................................................................................................... observations ........................................................................................................................ [2] [Total: 9]

Mark scheme: 2(a)(i) values between 115 °C and 335 °C (inclusive of these values) 1 2(a)(ii) values between 4.95 and 15.0 (inclusive of these values) 1 2(a)(iii) liquid (1) 50 C is between the melting point and boiling point / 50 C is above the melting point and below the boiling point / 50 C is higher than melting point but lower than boiling point / melting point below 50 C and boiling point above (1) 2 2(b)(i) iodine (1) potassium bromide (1) 2 2(b)(ii) bromine is more reactive than iodine / iodine is less reactive than bromine 1 2(b)(iii) add (nitric acid and) silver nitrate (1) yellow precipitate (1) 2

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3 (a) Water from natural sources can contain metal compounds and phosphates. (i) Name two other substances found in water which are harmful to aquatic life. 1 .......................................................................................................................................... 2 .......................................................................................................................................... [2] (ii) State why phosphates are harmful to aquatic life. ....................................................................................................................................... [1] (b) Table 3.1 shows the masses of ions, in mg, present in a 1000 cm3 sample of polluted water. Table 3.1 mass of ion present formula name of ion in mg / 1000 cm3 of of ion polluted water ammonium NH4+ 0.5 calcium Ca2+ 1.8 chloride Cl – 2.0 copper(II) Cu2+ 0.3 hydrogencarbonate HCO3– 8.0 magnesium Mg2+ 1.6 NO3– 0.6 potassium K+ 8.3 silicate SiO32– 5.0 sodium Na+ 5.2 sulfate SO42– 0.2 Answer these questions using information from Table 3.1. (i) Name the positive ion present in the highest concentration. ....................................................................................................................................... [1] (ii) State the name of the NO3– ion. ....................................................................................................................................... [1] (iii) Calculate the mass of magnesium ions present in 250 cm3 of polluted water. mass = .............................. mg [1] (c) Water is produced when blue copper(II) sulfate is heated. CuSO4•5H2O(s) CuSO4(s) + 5H2O(l) blue copper(II) white copper(II) sulfate sulfate (i) Describe how white copper(II) sulfate can be changed to blue copper(II) sulfate. ....................................................................................................................................... [1] (ii) Choose a word from the list which best describes white copper(II) sulfate. Draw a circle around your chosen answer. anhydrous aqueous hydrated oxidised [1] (d) Complete the symbol equation for the reaction of calcium with water. Ca + ......H2O → Ca(OH)2 + .............. [2] [Total: 10]

Mark scheme: 3(a)(i) 1 mark each for any two of:  plastics  sewage  microbes 2 3(a)(ii) deoxygenation of water / remove oxygen from water 1 3(b)(i) potassium 1 3(b)(ii) nitrate 1 3(b)(iii) 0.4 (mg) 1 3(c)(i) add water 1 3(c)(ii) anhydrous 1 3(d) 2(H2O) (1) H2 (1) 2

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4 This question is about chlorine and compounds of chlorine. (a) Chlorine has diatomic molecules. Define the term diatomic. .............................................................................................................................................. [1] (b) Deduce the number of protons, neutrons and electrons in the chloride ion shown. 1737Cl – number of protons ...................................................................................................................... number of neutrons .................................................................................................................... number of electrons ................................................................................................................... [3] (c) Chlorine reacts with hydrogen to produce hydrogen chloride. The reaction is exothermic. (i) State the meaning of the term exothermic. ............................................................................................................................................. ....................................................................................................................................... [2] (ii) Fig. 4.1 shows an incomplete reaction pathway diagram for the reaction of chlorine with hydrogen. energy progress of reaction Fig. 4.1 Complete Fig. 4.1 by writing these formulae on the diagram: ● Cl 2 + H2 ● 2HCl. [1] (iii) Explain how Fig. 4.1 shows that the reaction is exothermic. ............................................................................................................................................. ....................................................................................................................................... [1] (d) A few drops of methyl orange indicator are added to dilute hydrochloric acid. State the colour of the solution. .............................................................................................................................................. [1] (e) Dilute hydrochloric acid reacts with sodium hydroxide. (i) Complete the word equation for this reaction. hydrochloric sodium ........................ + → + ........................ acid hydroxide ........................ [2] (ii) Sodium hydroxide is an alkali. Write the formula of the ion present in all alkalis. ....................................................................................................................................... [1] (f) Fig. 4.2 shows the apparatus used for the electrolysis of concentrated aqueous sodium chloride using graphite electrodes. + power – supply Fig. 4.2 (i) Label Fig. 4.2 to show: ● the anode ● the electrolyte. [2] (ii) Name the products and state the observations at the positive and negative electrodes. product at the positive electrode ............................................................................................................................................. observations at the positive electrode ............................................................................................................................................. product at the negative electrode ............................................................................................................................................. observations at the negative electrode ............................................................................................................................................. [4] [Total: 18]

Mark scheme: 4(a) (molecule) containing two atoms / (molecule) has two atoms 1 4(b) protons: 17 (1) neutrons: 20 (1) electrons: 18 (1) 3 4(c)(i) reaction that transfers thermal energy / reaction that gives out heat (1) to the surroundings (1) 2 Question Answer Marks 4(c)(ii) Cl2 + H2 on left horizontal line AND 2HCl on right horizontal line 1 4(c)(iii) the energy of the reactants is greater than the energy of the product / the energy of Cl2 + H2 is greater than the energy of HCl / the energy of the products is less than the energy of the reactants 1 4(d) red / pink 1 4(e)(i) sodium chloride (1) water (1) 2 4(e)(ii) OH- 1 4(f)(i) left hand electrode labelled anode (1) electrolyte labelled (1) 2 4(f)(ii) product at anode: chlorine (1) observations at anode: green gas / bubbles (1) product at cathode: hydrogen (1) observations at cathode: bubbles (1) 4

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5 This question is about metals. (a) Carbon is used to extract iron from iron ore in a blast furnace. (i) Name the main ore of iron. ....................................................................................................................................... [1] (ii) Iron(III) oxide in the iron ore is reduced by carbon monoxide. Name the two substances which react in the blast furnace to produce carbon monoxide. ................................................................ and ��������������������������������������������������������������� [2] (b) Iron rusts in the presence of oxygen and water. State one method of preventing rusting. .............................................................................................................................................. [1] (c) Table 5.1 shows some information about the reaction of four metals with steam. Table 5.1 metal reaction with steam when metal is cold beryllium reacts slowly chromium reacts slowly only when the metal is very hot magnesium reacts rapidly silver no reaction Put the four metals in order of their reactivity. Put the least reactive metal first. least reactive most reactive [2] [Total: 6]

Mark scheme: 5(a)(i) hematite 1 5(a)(ii) carbon (1) carbon dioxide (1) 2 5(b) coating with plastic / painting / greasing / galvanising 1 5(c) silver<chromium<beryllium <magnesium (1) if 2 marks not scored: 1 mark for 1 pair reversed (consecutive) OR magnesium<beryllium<chromium<silver 2

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6 (a) A student investigates the reaction of different-sized pieces of calcium carbonate with dilute hydrochloric acid. The sizes of the pieces of calcium carbonate are: ● large ● medium ● small. All other conditions stay the same. Table 6.1 shows the time taken for each reaction to finish. Table 6.1 size of pieces of time taken for the calcium carbonate reaction to finish / s 160 50 450 (i) Complete Table 6.1 by writing the sizes of the pieces of calcium carbonate in the first column. [1] (ii) Describe the effect on the time taken for small pieces of calcium carbonate to finish reacting with dilute hydrochloric acid when the temperature is increased. All other conditions stay the same. ....................................................................................................................................... [1] (iii) Describe the effect on the time taken for small pieces of calcium carbonate to finish reacting with dilute hydrochloric acid when the concentration of hydrochloric acid is decreased. All other conditions stay the same. ....................................................................................................................................... [1] (b) Crystals of calcium chloride can be prepared by reacting excess calcium carbonate with dilute hydrochloric acid. Name the process used to separate the unreacted calcium carbonate from the rest of the reaction mixture. .............................................................................................................................................. [1] (c) Calcium carbonate is insoluble in water. Choose one other compound that is insoluble in water. Tick (✓) one box. ammonium sulfate potassium nitrate silver chloride sodium hydroxide [1] [Total: 5]

Mark scheme: 6(a)(i) medium small large 1 6(a)(ii) takes shorter time / less time taken 1 6(a)(iii) takes longer time / more time taken 1 6(b) filtration 1 6(c) 3rd box down ticked (silver chloride) 1

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7 (a) Fig. 7.1 shows the displayed formula of compound D. O C H H O C C H H C O H C O O H Fig. 7.1 (i) On Fig. 7.1 draw a circle around the alcohol functional group. [1] (ii) Deduce the molecular formula of compound D. ....................................................................................................................................... [1] (iii) Explain, by referring to the structure in Fig. 7.1, why compound D is unsaturated. ....................................................................................................................................... [1] (b) Ethene is also an unsaturated compound. (i) Draw the displayed formula of ethene. [1] (ii) Describe a test for unsaturated compounds. test ...................................................................................................................................... observations ........................................................................................................................ [2] (c) Ethene can be manufactured by cracking larger alkane molecules. (i) State two conditions for cracking. 1 .......................................................................................................................................... 2 .......................................................................................................................................... [2] (ii) Complete the symbol equation for the cracking of decane, C10H22, to produce ethene and one other hydrocarbon. C10H22 → C2H4 + ................ [1] (d) Ethanol can be manufactured by the reaction of ethene with steam. Name one other method of manufacturing ethanol. .............................................................................................................................................. [1] (e) Ethanol can be oxidised to ethanoic acid. Ethanoic acid reacts with sodium. Name the salt formed when ethanoic acid reacts with sodium. .............................................................................................................................................. [1] (f) Ethanoic acid reacts with propanol. The organic product has the molecular formula C5H10O2. Complete Table 7.1 to calculate the relative molecular mass of C5H10O2. Table 7.1 relative atom number of atoms atomic mass carbon 12 hydrogen 1 oxygen 2 16 2 × 16 = 32 relative molecular mass = .............................. [2] [Total: 13]

Mark scheme: 7(a)(i) circle around OH group 1 7(a)(ii) C5H6O5 1 7(a)(iii) has a C=C bond / has a carbon – carbon double bond 1 Question Answer Marks 7(b)(i) 1 7(b)(ii) aqueous bromine (1) turns colourless / decolourises (1) 2 7(c)(i) catalyst (1) high temperature (1) 2 7(c)(ii) C8H18 1 7(d) fermentation 1 7(e) sodium ethanoate 1 7(f) 102 (2) If 2 marks not scored 1 mark for 60 (for C) OR 10 (for H) 2

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8 This question is about non-metals and compounds of non-metals. (a) Describe two physical properties which are typical of non-metals. 1 ................................................................................................................................................. 2 ................................................................................................................................................. [2] (b) Methane is a compound of carbon and hydrogen. (i) Complete Fig. 8.1 to show the dot-and-cross diagram for a molecule of methane. Show outer shell electrons only. H H C H H Fig. 8.1 [1] (ii) Methane is an alkane. Write the general formula for alkanes. ....................................................................................................................................... [1] (iii) Methane is an air pollutant. State one source of methane in the air. ....................................................................................................................................... [1] (iv) State one adverse effect of methane in the air. ....................................................................................................................................... [1] (v) Carbon particulates and water are two of the products of the incomplete combustion of methane. Name one other compound formed during the incomplete combustion of methane. ....................................................................................................................................... [1] (c) Sulfur dioxide is an air pollutant which contributes to acid rain. (i) Choose from the list the pH value that is acidic. Draw a circle around your chosen answer. pH 4 pH 7 pH 9 pH 13 [1] (ii) State two methods of reducing acid rain. 1 .......................................................................................................................................... 2 .......................................................................................................................................... [2] (iii) Sulfur dioxide gas turns aqueous acidified potassium manganate(VII) from purple to colourless. Fig. 8.2 shows a gas jar of sulfur dioxide separated from a gas jar of air by a glass plate. A piece of filter paper soaked in aqueous acidified potassium manganate(VII) is glued to the top of the gas jar of air. filter paper soaked in aqueous acidified potassium manganate(VII) air glass plate sulfur dioxide glass plate present a short time after the glass plate is removed Fig. 8.2 The glass plate is removed. At first, the filter paper remains purple. After a short time, the filter paper turns colourless. Explain these results in terms of the kinetic particle theory. ............................................................................................................................................. ............................................................................................................................................. ............................................................................................................................................. ............................................................................................................................................. ....................................................................................................................................... [3] [Total: 13]

Mark scheme: 8(a) 1 mark each for any 2 of:  poor thermal conductor / poor conductor of heat  poor electrical conductor  not malleable / brittle  not ductile  low melting point / low boiling point Question Answer Marks 8(b)(i) pair of electrons between each H and C and no other electrons on the H atoms 1 8(b)(ii) CnH2n+2 1 8(b)(iii) decomposition of vegetation / waste gases from digestion in animals 1 8(b)(iv) (increased) global warming / climate change 1 8(b)(v) carbon monoxide 1 8(c)(i) pH 4 1 8(c)(ii) 1 mark each for any two of:  catalytic converters  low sulfur fuels  flue gas desulfurisation 2 8(c)(iii) 1 mark each for any 3 of:  diffusion  molecules in (constant) movement / molecules collide / molecules travel  (movement of) molecules is random / molecules (move) in every direction  molecules spread out / molecules mix  molecules hit filter paper / reach filter paper  (molecules spread) from higher concentration to lower concentration / down concentration gradient 3

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