Cambridge IGCSE Chemistry (9-1) 0971 — 2018 May/June Paper 3 · Variant 1

1 The names of eight gases are given. ammonia argon carbon dioxide helium hydrogen methane neon sulfur dioxide (a) Answer the following questions about these gases. Each gas may be used once, more than once or not at all. State which gas: (i) turns damp red litmus paper blue ....................................................................................................................................... [1] (ii) contributes to the formation of acid rain ....................................................................................................................................... [1] (iii) is a hydrocarbon which contributes to climate change ....................................................................................................................................... [1] (iv) is a product of the reaction of copper(II) carbonate with hydrochloric acid ....................................................................................................................................... [1] (v) is a monatomic gas which has atoms with the electronic structure 2,8,8. ....................................................................................................................................... [1] (b) (i) Explain why helium and not hydrogen is used to fill party balloons. ....................................................................................................................................... [1] (ii) Give one use of argon. ....................................................................................................................................... [1] (c) Carbon dioxide is a compound. What is meant by the term compound ? .................................................................................................................................................... .............................................................................................................................................. [1] (d) Complete the dot-and-cross diagram to show the electron arrangement in a molecule of ammonia. Show outer shell electrons only. H N H H [2] [Total: 10]

Mark scheme: 1(a)(i) ammonia / NH3 1 1(a)(ii) sulfur dioxide / SO2 1 1(a)(iii) methane / CH4 1 1(a)(iv) carbon dioxide / CO2 1 1(a)(v) argon / Ar 1 1(b)(i) helium is inert / it is inert / helium is unreactive / hydrogen is flammable 1 1(b)(ii) (old) light bulbs / welding / to protect reactive metals from oxidation / lasers 1 1(c) (substance containing) two (or more) types of atom bonded / two (or more) types of atom joined / two (or more) types of atoms chemically combined 1 1(d) pair of bonding electrons between each N and H 1 two unpaired electrons on N AND no extra electrons on the H 1

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2 The table shows the percentage by volume of each of the gases present in the exhaust gases from a petrol engine. name percentage by volume carbon monoxide 1.0 carbon dioxide hydrogen 0.2 nitrogen 77.0 nitrogen dioxide 0.3 oxygen 0.7 hydrocarbons 0.3 water vapour 5.0 total 100.0 (a) (i) Calculate the percentage by volume of carbon dioxide in the exhaust gases. ..............................% [1] (ii) Which gas shown in the table is present in the lowest percentage by volume? ....................................................................................................................................... [1] (iii) Which two elements in the table combine to form nitrogen dioxide? ............................................................... and ................................................................ [1] (iv) Give the formula for nitrogen dioxide. ....................................................................................................................................... [1] (v) Where does the nitrogen in the exhaust gases come from? ....................................................................................................................................... [1] (b) The carbon monoxide in the exhaust gases comes from the incomplete combustion of hydrocarbons. (i) What is meant by the term hydrocarbon? ............................................................................................................................................. ....................................................................................................................................... [2] (ii) Give one adverse effect of carbon monoxide on health. ....................................................................................................................................... [1]

Mark scheme: 2(a)(i) 15.5(%) 1 2(a)(ii) hydrogen / H2 1 2(a)(iii) nitrogen AND oxygen 1 2(a)(iv) NO2 1 2(a)(v) the air / the atmosphere 1 Question Answer Marks 2(b)(i) compound of carbon and hydrogen only / compound of hydrogen and carbon with no other elements IF 2 marks not scored: 1 mark for it contains carbon and hydrogen only / compound of hydrogen and carbon / molecules containing carbon and hydrogen 2 2(b)(ii) poisonous / toxic 1 2(b)(iii) 5 (CO2) 1 6 (H2O) 1

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3 Limonene is a volatile liquid which smells of oranges. (a) A teacher placed a beaker of limonene at the front of a classroom. At first, the students at the back of the classroom could not smell the limonene. After two minutes, the smell of limonene had spread throughout the classroom. The air in the classroom was still and calm. (i) Explain these observations using the kinetic particle model. ............................................................................................................................................. ............................................................................................................................................. ............................................................................................................................................. ............................................................................................................................................. ....................................................................................................................................... [3] (ii) The melting point of limonene is –74 °C. The boiling point of limonene is 176 °C. What is the physical state of limonene at – 80 °C? Explain your answer. ............................................................................................................................................. ....................................................................................................................................... [2] (b) An enzyme present in peppermint plants is a catalyst for the oxidation of limonene. State what is meant by the terms: (i) catalyst ............................................................................................................................................. ....................................................................................................................................... [1] (ii) oxidation ............................................................................................................................................. ....................................................................................................................................... [1] (c) Limonene can be made from a colourless compound called α-terpineol. The structure of α-terpineol is shown. H H H CH3 C C C OH H3C C C C C H CH3 H H H H (i) What feature of the structure of the α-terpineol molecule shows that it is an unsaturated compound? ....................................................................................................................................... [1] (ii) Describe how the colour of aqueous bromine changes when an excess of α-terpineol is added to it. from .............................................................. to ................................................................. [2] [Total: 10]

Mark scheme: 3(a)(i) One mark each for any 3 of: • (limonene) particles go from liquid to vapour • diffusion • random movement of particles / particles move anywhere / particles move in all directions • spreading out of particles / intermingling of particles / mixing of particles / particles collide / particles bounce off each other / particles go all over • (bulk) movement of particles from higher to lower concentration / movement of particles down concentration gradient 3 3(a)(ii) solid 1 – 80 ºC is below the melting point / it is below the melting point / it has not yet reached its melting point / melts above – 80 ºC 1 3(b)(i) (substance which) speeds up a reaction / substance which increases the rate of reaction 1 3(b)(ii) addition of oxygen (to a substance) / loss of electrons / increase in oxidation number 1 Question Answer Marks 3(c)(i) C=C bond 1 3(c)(ii) orange / red-brown / brown 1 to colourless 1

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4 This question is about iron and its compounds. (a) The table shows how easy it is to reduce four metal oxides by heating with carbon. metal oxide ease of reduction with carbon chromium(III) oxide only reduced above 1700 °C iron(III) oxide only reduced above 650 °C magnesium oxide not reduced at 1750 °C nickel(II) oxide only reduced above 300 °C Use this information to put the metals in order of their reactivity. Put the least reactive metal first. least reactive most reactive [2] (b) Iron is a transition element. Potassium is an element in Group I of the Periodic Table. Describe three ways in which the properties of iron differ from those of potassium. 1 ................................................................................................................................................. 2 ................................................................................................................................................. 3 ................................................................................................................................................. [3] (c) Iron wire burns in oxygen. Balance the chemical equation for this reaction. .....Fe + .....O2 Fe3O4 [2] (d) Pure iron can be made by reducing iron(III) oxide, Fe2O3, with hydrogen. Fe2O3 + 3H2 2Fe + 3H2O How does this equation show that iron(III) oxide is reduced? .................................................................................................................................................... .............................................................................................................................................. [1] (e) When iron reacts with dilute hydrochloric acid, iron(II) chloride is formed. (i) Describe a test for iron(II) ions. test ...................................................................................................................................... result ................................................................................................................................... [2] (ii) Another chloride of iron has the structure shown. Cl Cl Cl Fe Fe Cl Cl Cl Deduce the molecular formula of this compound showing the number of iron and chlorine atoms. ....................................................................................................................................... [1] (f) Some iron nails were placed in bottles under different conditions. A B C D moist boiled air water water iron nails anhydrous calcium chloride to dry the air In which bottles will the iron nails not rust? Give reasons for your answer. .................................................................................................................................................... .................................................................................................................................................... .............................................................................................................................................. [2] [Total: 13]

Mark scheme: 4(a) nickel<iron<chromium<magnesium IF 2 marks not scored: 1 mark if all reversed / one consecutive pair reversed 2 4(b) One mark each for any 3 of: • iron has high melting point / boiling point / ORA for K • iron has high density / ORA for K • iron has catalytic activity / ORA for K • iron forms coloured compounds / ORA for K • iron compounds have variable oxidation states / form ions with different charges / ORA for K • iron is hard / potassium is soft / iron is strong / potassium is weak • one suitable difference in chemical properties e.g. iron is less reactive than potassium ORA / potassium reacts with cold water / iron does not react with cold water / iron rusts / potassium does not rust • iron is magnetic / ORA for K 3 Question Answer Marks 4(c) 3 (Fe) 1 2 (O2) 1 4(d) it loses oxygen / oxygen is removed from the iron oxide / hydrogen gains the oxygen from the iron oxide 1 4(e)(i) add (aqueous) sodium hydroxide / (aqueous) ammonia AND green precipitate (2) IF 2 marks not scored: 1 mark for add (aqueous) sodium hydroxide / (aqueous) ammonia 2 4(e)(ii) Fe2Cl 6 1 4(f) B / boiled water AND because no air / no oxygen 1 C / with calcium chloride AND because no water 1

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5 (a) Complete the sentence about electrolysis using words from the list. breakdown compound electricity electroplating element gaseous heat molten Electrolysis is the .............................. of an ionic .............................. when .............................. or in aqueous solution by the passage of .............................. . [4] (b) Molten zinc iodide can be electrolysed using the apparatus shown. + – On the diagram, label: ●● the anode ●● the cathode ●● the electrolyte [2] (c) Why are the electrodes made of graphite? .............................................................................................................................................. [1] (d) Predict the products of the electrolysis of molten zinc iodide at: the negative electrode ................................................................................................................ the positive electrode. ................................................................................................................ [2] (e) When chlorine is bubbled through a colourless aqueous solution of zinc iodide, the solution turns brown. Name the brown substance. Suggest, using ideas about reactivity of the halogens, why this reaction occurs. .................................................................................................................................................... .............................................................................................................................................. [2] [Total: 11]

Mark scheme: 5(a) breakdown 1 compound 1 molten 1 electricity 1 5(b) + electrode labelled anode and – electrode labelled cathode 1 liquid labelled electrolyte 1 Question Answer Marks 5(c) graphite / it conducts electricity 1 5(d) negative electrode: zinc / Zn 1 positive electrode: iodine / I2 1 5(e) iodine 1 chlorine is more reactive than iodine ORA 1

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6 This question is about isotopes. (a) An atom of an isotope of fluorine is represented by the symbol shown. 19F9 Describe the structure of an atom of this isotope of fluorine. In your answer, include: ●● the position of the protons, neutrons and electrons in the atom ●● the number of protons, neutrons and electrons present in the atom. .................................................................................................................................................... .................................................................................................................................................... .................................................................................................................................................... .................................................................................................................................................... .................................................................................................................................................... .................................................................................................................................................... .............................................................................................................................................. [5] (b) Complete the sentence about isotopes using words from the list. atomic compound element ions molecular nucleons Isotopes are atoms of the same .............................. which have the same .............................. number but different numbers of .............................. . [3] (c) Give one medical use of radioactive isotopes. .............................................................................................................................................. [1] (d) Which one of the following isotopes is used as a source of energy? Draw a circle around the correct answer. 127I53 235U92 131Xe54 3066Zn [1] [Total: 10]

Mark scheme: 6(a) One mark each for any 5 of: • protons in the nucleus / centre (of the atom) • neutrons in the nucleus / centre (of the atom) • electrons outside the nucleus / electrons surrounding the nucleus / electrons orbiting the nucleus • 9 protons • 9 electrons • 10 neutrons 5 6(b) element 1 atomic 1 nucleons 1 6(c) any suitable e.g. treating cancer / checking thyroid function / tracer (in the body) 1 Question Answer Marks 6(d) 235 U 92 1

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7 This question is about Group I elements and their compounds. (a) The properties of some Group I elements are shown in the table. boiling point atomic radius relative thermal observations when it element / °C / pm conductivity reacts with cold water rapid bubbling but does sodium 883 186 3.9 not burst into flame very rapid bubbling and potassium 759 227 bursts into flame rubidium 688 1.6 caesium 671 265 1.0 explodes (i) Complete the table to estimate: ●● the relative thermal conductivity of potassium ●● the atomic radius of rubidium. [2] (ii) Describe the trend in the boiling points of the Group I elements. ....................................................................................................................................... [1] (iii) Use the information in the table to predict what you would observe when rubidium reacts with cold water. ....................................................................................................................................... [1] (b) Which one of the statements about the formation of a sodium ion from a sodium atom is correct? Tick one box. A sodium atom gains an electron. A sodium atom loses an electron. A sodium atom loses a proton. A sodium atom gains a proton. [1] (c) Is sodium oxide an acidic oxide or a basic oxide? Give a reason for your answer. .................................................................................................................................................... .............................................................................................................................................. [1] (d) A compound of sodium has the formula C4H5Na. Calculate the relative formula mass of C4H5Na. Show all your working. Use your Periodic Table to help you. relative formula mass = .............................. [2] (e) Complete the word equation for the reaction of sodium hydroxide with sulfuric acid. sodium sulfuric .............................. .............................. + + hydroxide acid .............................. [2] [Total: 10]

Mark scheme: 7(a)(i) atomic radius of Rb: any value between 228 and 264 (inclusive of these values) 1 relative thermal conductivity of K: any value between 3.8 and 1.7 (inclusive of these values) 1 7(a)(ii) decreases down (the Group) / increases up (the Group) / decreases from sodium to caesium ORA 1 7(a)(iii) bursts into flame / extremely rapid bubbling / explodes 1 7(b) second box down ticked (a sodium atom loses an electron) 1 7(c) basic oxide because metallic oxides are basic 1 7(d) 76 IF 2 marks not scored: 1 mark for (C =) 12, (H =) 1 (Na =) 23 2 7(e) sodium sulfate 1 water 1

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8 When zinc reacts with hydrochloric acid, hydrogen gas is produced. The graph shows how the volume of hydrogen gas produced changes with time when an excess of zinc is reacted with 0.2 mol / dm3 hydrochloric acid. 80 60 volume of hydrogen 40 gas / cm3 20 0 0 2 4 6 8 10 12 time / min (a) Explain why the volume of hydrogen gas remains constant after six minutes. .............................................................................................................................................. [1] (b) What volume of hydrogen gas was released in the first two minutes of the reaction? .............................................................................................................................................. [1] (c) The experiment is repeated using the same volume of 0.1 mol / dm3 hydrochloric acid. All other conditions are kept the same. On the grid, draw the graph for the experiment using 0.1 mol / dm3 hydrochloric acid. [2] (d) Give the name of the salt formed when zinc reacts with hydrochloric acid. .............................................................................................................................................. [1] (e) Which one of the following pH values could be the pH of dilute hydrochloric acid? Draw a circle around the correct answer. pH 1 pH 7 pH 9 pH 13 [1] [Total: 6]

Mark scheme: 8(a) the reaction is complete / the reaction has finished 1 8(b) any value between and including 37 (cm3) to 38 (cm3) 1 Question Answer Marks 8(c) line starts from 0 cm3 AND initial gradient less steep 1 final volume levels off between 24–30 cm3 OR line below 27 cm3 AND gradient becoming less steep at a later point 1 8(d) zinc chloride 1 8(e) pH 1 1

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