1 Choose from the following chlorides to answer the questions. aluminium chloride ammonium chloride cobalt(II) chloride hydrogen chloride iron(III) chloride potassium chloride silver chloride sodium chloride Each chloride may be used once, more than once or not at all. State which chloride: (a) contains a cation with a charge of 2+ … [1] (b) reacts with aqueous sodium hydroxide to form a red-brown precipitate … [1] (c) is insoluble in water … [1] (d) reacts with sodium hydroxide when warmed to produce a gas which turns damp red litmus paper blue … [1] (e) when added to water can form an aqueous solution with a pH of 1. … [1] [Total: 5]

1(a) cobalt(II) chloride 1 1(b) iron(III) chloride 1 1(c) silver chloride 1 1(d) ammonium chloride 1 1(e) hydrogen chloride 1 (a) To earn this mark, you must correctly identify the chloride containing a cation with a 2+ charge. (b) To earn this mark, you must correctly identify the chloride that forms a red-brown precipitate with aqueous sodium hydroxide. (c) To earn this mark, you must correctly identify the chloride that is insoluble in water. (d) To earn this mark, you must correctly identify the chloride that produces ammonia gas (which turns damp red litmus blue) when warmed with sodium hydroxide. (e) To earn this mark, you must correctly identify the chloride that forms a strongly acidic solution (pH 1) when added to water.

2 Helium, neon, argon, krypton, xenon and radon are noble gases in Group VIII. (a) Name the noble gas which has the greatest volume composition in air. … [1] (b) State one use for helium. … [1] (c) Radon is very unreactive. Use the electronic structure of radon to explain why. … … [1] (d) Two isotopes of radon are shown. 220 86Rn 222 86Rn (i) Give one similarity in the atomic structure of these two isotopes. … [1] (ii) Give one difference in the atomic structure of these two isotopes. … [1] (e) Xenon forms a compound that contains only xenon, oxygen and fluorine. The compound contains 22.1% oxygen by mass and 17.5% fluorine by mass. Calculate the empirical formula of this compound. empirical formula … [3] (f) A sample of neon has a volume of 21 dm3 at room temperature and pressure. (i) The temperature of the sample is increased. The pressure remains constant. Describe and explain, using kinetic particle theory, what happens to the volume of the sample. … … [1] (ii) The pressure of the sample is increased. The temperature remains constant. Describe and explain, using kinetic particle theory, what happens to the volume of the sample. … … [1] (iii) Calculate the mass of neon in the 21 dm3 sample. Give your answer to two significant figures. mass … g [2] [Total: 12]

2(a) argon 1 2(b) (air) balloons / undersea breathing apparatus 1 2(c) outer shell has 8 electrons 1 2(d)(i) 86 protons / 86 electrons / same electronic structure 1 2(d)(ii) radon-222 has two more neutrons / radon-220 has two fewer neutrons / radon-220 has 134 neutrons and radon-222 has 136 neutrons 1 2(e) percentage of xenon = 60.4 (1) mole ratio Xe : O : F is 60.4 / 130 : 22.1 / 16 : 17.5 / 19 OR 0.46 : 1.38 : 0.92 (1) empirical formula XeO3F2 (1) 3 2(f)(i) volume increases AND particles move faster / particles spread out more / particles move further apart 1 2(f)(ii) volume decreases AND particles move closer together / distance between particles decreases 1 2(f)(iii) moles = 21 / 24 OR 0.875 (1) mass = 18 (g) (1) 2 To earn marks, you must correctly name argon, state a valid use for helium, explain radon's unreactivity by mentioning its full outer electron shell, identify a similarity (protons/electrons/electronic structure) and a difference (number of neutrons) between the isotopes, and correctly calculate the empirical formula by showing the percentage of xenon, the mole ratios, and the final formula. For parts (f)(i) and (f)(ii), you need to state the change in volume and explain it in terms of particle movement. For (f)(iii), you must correctly calculate the moles and then the mass.

2 Oxygen, sulfur, selenium, tellurium and polonium are in Group VI. (a) State the percentage composition by volume of oxygen in dry air. … [1] (b) State one large-scale use for oxygen. … [1] (c) Two isotopes of polonium are shown. 20 8 9 4Po 21 8 0 4Po (i) Explain why both isotopes have the same chemical properties. … [1] (ii) Give one difference in the atomic structure of these two isotopes. … [1] (d) Selenium forms a compound that contains only selenium, oxygen and chlorine. The compound contains 9.6% oxygen by mass and 42.8% chlorine by mass. Calculate the empirical formula of this compound. empirical formula … [3] (e) A sample of oxygen has a volume of 11.5 dm3 at room temperature and pressure. (i) The temperature of the sample is decreased. The pressure remains constant. Describe and explain, using kinetic particle theory, what happens to the volume of the sample. … … [1] (ii) The pressure of the sample is decreased. The temperature remains constant. Describe and explain, using kinetic particle theory, what happens to the volume of the sample. … … [1] (iii) Calculate the mass of oxygen in the 11.5 dm3 sample at room temperature and pressure. Give your answer to two significant figures. mass … g [2] [Total: 11]

2(a) 21 (%) 1 2(b) steel making / welding / cutting metals / oxygen tents in hospitals / breathing apparatus / fuel cells 1 2(c)(i) same electronic structure / same electronic configuration 1 2(c)(ii) polonium-210 has one more neutron / polonium-209 has one less neutron / polonium-209 has 125 neutrons and polonium- 210 has 126 neutrons 1 2(d) percentage of selenium = 47.6 (1) mole ratio Se : O : Cl is 47.6 / 79 : 9.6 / 16 : 42.8 / 35.5 OR 0.60 : 0.60 : 1.21 (1) empirical formula SeOCl 2 (1) 3 2(e)(i) volume decreases AND particles move slower / particles less spread out / particles closer together 1 2(e)(ii) volume increases AND particles move further apart / particles more spread out / distance between particles increases 1 2(e)(iii) mol = 11.5 / 24 OR 0.479(117) (1) mass = 15 (g) (1) 2 To earn marks, you must provide the correct percentage for oxygen in air, state a valid large-scale use for oxygen, explain that isotopes have the same chemical properties due to identical electronic structures, and identify the difference in neutron count between the given isotopes. For the empirical formula calculation, you need to correctly calculate the percentage of selenium, determine the mole ratios, and then state the correct empirical formula. For part (e)(i), you must state that the volume decreases and explain this using kinetic particle theory by mentioning particles moving slower or being closer together. For part (e)(ii), you must state that the volume increases and explain this by mentioning particles moving further apart or being more spread out. For part (e)(iii), you must correctly calculate the moles of oxygen and then use this to find the mass.

4 Copper(II) chloride, copper(II) iodide and copper(II) carbonate are ionic compounds. (a) Predict two physical properties, other than electrical conductivity, of copper(II) chloride. 1. … 2. … [2] (b) Copper is a transition element. Suggest one property of copper(II) chloride that is characteristic of a compound of a transition element. … [1] (c) Copper reacts with chlorine to make copper(II) chloride. Cu + Cl 2 CuCl 2 Copper(II) chloride contains Cu2+ and Cl – ions. Explain, in terms of the movement of electrons, how CuCl 2 is formed from copper atoms and chlorine molecules. … … … [2] (d) Copper(II) iodide decomposes to make iodine and copper(I) iodide. The ionic equation for this reaction is shown. 2Cu2+ + 4I– 2CuI + I2 (i) Use the information to explain that oxidation takes place. … … [1] (ii) Use the information to explain that reduction takes place. … … [1] (e) A sample of copper(II) carbonate is heated strongly. Name the products of this reaction. … [1] [Total: 8]

4(a) Any two from: soluble in water (1) insoluble in organic solvents (1) high melting point / solid at room temperature (1) 2 4(b) coloured / forms a blue ppt with NaOH or NH3 1 4(c) copper loses electrons and chlorine gains electrons (1) reference to (transfer of) two electrons (1) 2 4(d)(i) iodide (ion) loses electrons 1 4(d)(ii) Cu2+ (ion) gains electrons / copper(II) ions gain electrons 1 4(e) copper(II) oxide AND carbon dioxide 1 To earn marks, you must state two correct physical properties of copper(II) chloride, suggest a characteristic property of a transition element compound, explain the formation of CuCl2 by describing electron loss from copper and gain by chlorine (specifically two electrons), and correctly identify that iodide ions lose electrons and Cu2+ ions gain electrons. For the final part, you must correctly name both products of the decomposition.

Cambridge O Level Chemistry · 5070

O-Level Chemistry (5070) The Periodic Table past paper questions

Revise O-Level Chemistry (5070) — The Periodic Table with real Cambridge past-paper questions grouped by topic, each shown with its marking scheme. Working one topic at a time targets exactly the skill each question tests.

142 free questions from 2016–2021, each with its marking scheme. Open the full topical bank to filter by subtopic, paper, and year.

The Periodic Table in O-Level Chemistry 5070 exams, 2020–2025

Across 2020–2025, The Periodic Table accounted for 116 questions worth 610 marks in Cambridge O Level Chemistry (5070) papers.

By year
Year	Questions	Marks
2020	15	87
2021	29	136
2022	15	63
2023	15	69
2024	17	84
2025	25	171

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Paper 1 · 61 qs
Paper 2 · 41 qs
Paper 3 · 5 qs
Paper 4 · 9 qs

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2021 Oct/Nov · Paper 2 · Q1 · 5 marks
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2021 May/Jun · Paper 2 · Q2 · 12 marks
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2021 May/Jun · Paper 2 · Q2 · 11 marks
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2021 May/Jun · Paper 2 · Q4 · 8 marks
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2021 May/Jun · Paper 1 · Q26 · 1 mark
Marking scheme
Mark scheme — 2021 Paper 1 Q26
Answer: D
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