1 Choose from the following oxides to answer the questions. aluminium oxide calcium oxide iron(II) oxide magnesium oxide silicon dioxide sodium oxide sulfur dioxide Each oxide may be used once, more than once or not at all. State which oxide: (a) has a simple molecular structure … [1] (b) is a coloured solid … [1] (c) contains ions with a 3+ charge … [1] (d) is a product of the thermal decomposition of calcium carbonate … [1] (e) contributes to acid rain. … [1] [Total: 5]

1(a) sulfur dioxide 1 1(b) iron(II) oxide 1 1(c) aluminium oxide 1 1(d) calcium oxide 1 1(e) sulfur dioxide 1 (a) To earn the mark, you must correctly identify sulfur dioxide as the oxide with a simple molecular structure. (b) To earn the mark, you must correctly identify iron(II) oxide as the coloured solid. (c) To earn the mark, you must correctly identify aluminium oxide as the oxide containing ions with a 3+ charge. (d) To earn the mark, you must correctly identify calcium oxide as the product of the thermal decomposition of calcium carbonate. (e) To earn the mark, you must correctly identify sulfur dioxide as the oxide that contributes to acid rain.

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.

2 Dry air contains nitrogen, oxygen, noble gases and carbon dioxide. (a) State the percentage of oxygen present in dry air. … [1] (b) Carbon dioxide is removed from a sample of air by passing the air through aqueous sodium hydroxide. Explain why aqueous sodium hydroxide removes carbon dioxide from air. … … … [2] (c) Describe how oxygen, nitrogen and the noble gases are separated from each other after carbon dioxide has been removed. … … [2] (d) Describe the test for oxygen. test … observation … [2] (e) Ozone, O3, is formed in the atmosphere by the reaction of nitrogen dioxide with oxygen in the presence of ultraviolet light. (i) State the type of chemical reaction that takes place when ozone is formed in this way. … [1] (ii) Nitrogen dioxide is formed in internal combustion engines. State one other source of nitrogen dioxide in the atmosphere. … [1] (f) A layer of ozone is present high in the atmosphere. State one problem for humans that can arise if the ozone layer is depleted by CFCs. … [1] [Total: 10]

2(a) 21(%) 1 2(b) carbon dioxide is an acidic oxide (1) reacts with base / reacts with alkali / neutralised by sodium hydroxide (1) 2 2(c) air liquefied (1) fractional distillation (1) 2 2(d) glowing splint (1) relights (1) 2 2(e)(i) photochemical / redox 1 2(e)(ii) lightning 1 2(f) (more) skin cancer / (more) sunburn / (more) harm to eyes 1 (a) To earn the mark, you must state the percentage of oxygen in dry air as 21%. (b) To earn the first mark, you must state that carbon dioxide is an acidic oxide. To earn the second mark, you must explain that it reacts with a base/alkali or is neutralised by sodium hydroxide. (c) To earn the first mark, you must state that air is liquefied. To earn the second mark, you must state that fractional distillation is used. (d) To earn the first mark, you must describe the test as using a glowing splint. To earn the second mark, you must state the observation that the splint relights. (e)(i) To earn the mark, you must state 'photochemical' or 'redox'. (e)(ii) To earn the mark, you must state 'lightning'. (f) To earn the mark, you must state a harmful effect like 'more skin cancer', 'more sunburn', or 'more harm to eyes'.

2 This question is about pollutant gases. (a) Hydrocarbons such as octane are used as fuels for cars. The list shows the gases present in a car exhaust. carbon dioxide carbon monoxide nitrogen nitrogen dioxide octane water vapour State which two gases in the list show that incomplete combustion has taken place in this car engine. 1 … 2 … [2] (b) Describe a test for carbon dioxide. test … observation … [2] (c) Two natural sources of methane in the atmosphere are from leaks of natural gas and waste gases from animals. Give one other natural source of methane in the atmosphere. … [1] (d) Complete this sentence about the effect of an increase in the concentration of methane in the atmosphere. Methane is a … gas because it absorbs and then re-emits infrared radiation. This contributes to an increase in temperature of the atmosphere which is called … … . [2] (e) Cars are fitted with catalytic converters to reduce the amount of harmful pollutant gases from car exhausts. Describe how catalytic converters remove pollutant gases from car exhausts. … … … … … [3] [Total: 10]

2(a) carbon monoxide (1) octane (1) 2 2(b) limewater (1) turns milky / turns cloudy / white precipitate (1) 2 2(c) decomposition of vegetation / decomposition of plants 1 2(d) greenhouse (1) global warming (1) 2 2(e) mention of nitrogen oxides and carbon monoxide (as the pollutants / reactants) (1) nitrogen / N2 (in exhaust gases) (1) carbon dioxide / CO2 (in exhaust gases) (1) 3 (a) To earn these two marks, you must identify both carbon monoxide and octane as the gases indicating incomplete combustion. (b) To earn these two marks, you must state that limewater is used for the test and that the observation is it turning milky or cloudy. (c) To earn this mark, you must state 'decomposition of vegetation' or 'decomposition of plants' as a natural source of methane. (d) To earn these two marks, you must correctly identify methane as a 'greenhouse' gas and state that its increased concentration leads to 'global warming'. (e) To earn these three marks, you must mention nitrogen oxides and carbon monoxide as the pollutants/reactants, and then state that nitrogen and carbon dioxide are present in the exhaust gases.

Cambridge O Level Chemistry · 5070

O-Level Chemistry (5070) Chemistry of the environment past paper questions

Revise O-Level Chemistry (5070) — Chemistry of the environment 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.

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

Chemistry of the environment in O-Level Chemistry 5070 exams, 2020–2025

Across 2020–2025, Chemistry of the environment accounted for 115 questions worth 482 marks in Cambridge O Level Chemistry (5070) papers.

By year
Year	Questions	Marks
2020	20	64
2021	19	104
2022	20	112
2023	22	95
2024	20	62
2025	14	45

Most-tested subtopics

Appears in

Paper 1 · 66 qs
Paper 2 · 48 qs
Paper 3 · 1 q

All most-tested Chemistry topics

2021 Oct/Nov · Paper 2 · Q1 · 5 marks
Marking scheme
Get Steven’s plain-English explanation
2021 May/Jun · Paper 2 · Q2 · 11 marks
Marking scheme
Get Steven’s plain-English explanation
2021 Oct/Nov · Paper 2 · Q2 · 10 marks
Marking scheme
Get Steven’s plain-English explanation
2021 Oct/Nov · Paper 2 · Q2 · 10 marks
Marking scheme
Get Steven’s plain-English explanation
2021 Oct/Nov · Paper 1 · Q3 · 1 mark
Marking scheme
Mark scheme — 2021 Paper 1 Q3
Answer: D
Get Steven’s plain-English explanation