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.

3 Iron powder reacts with dilute sulfuric acid. Fe(s) + H2SO4(aq) FeSO4(aq) + H2(g) (a) The graph shows the volume of hydrogen gas produced at 20 °C as the reaction proceeds. volume of hydrogen gas / cm3 40 30 20 10 0 4 8 12 16 20 24 28 time / min (i) State how long it takes from the start of the experiment to collect 18 cm3 of hydrogen gas. … [1] (ii) The experiment is repeated at 30 °C. All other conditions are the same. Draw a line on the grid to show how the volume of hydrogen gas produced changes with time when the reaction is done at 30 °C. [2] (b) (i) Describe and explain, using ideas about collisions between particles, how the rate of the reaction changes when the temperature of the reaction mixture is increased. All other conditions are the same. … … … … [2] (ii) Describe and explain, using ideas about collisions between particles, how the rate of the reaction changes when larger pieces of iron are used. All other conditions are the same. … … … … [2] (c) Calculate the maximum volume, in dm3, of hydrogen formed when 3.36 g of iron react with excess dilute sulfuric acid at room temperature and pressure. Give your answer to three significant figures. maximum volume = … dm3 [2] (d) Concentrated sulfuric acid is an oxidising agent. Describe a test for oxidising agents. test … observations … … [2] [Total: 11]

3(a)(i) 6 minutes 1 3(a)(ii) initial gradient steeper and starting from origin (1) line levels off at 34 cm3 gas (1) 2 3(b)(i) rate of reaction increases (no mark) and particles move faster / particles have more kinetic energy (1) more particles have activation energy (or above) / more successful collisions / more energetic collisions (1) 2 3(b)(ii) rate of reaction decreases (no mark) and fewer particles exposed on surface / fewer particles (of iron) per unit area / fewer particles per cm2 (1) collision frequency decreases / fewer particles collide per second / collision rate decreases / collisions less often (1) 2 3(c) mol iron = 3.36 56 OR 0.060 mol (1) volume of hydrogen = 1.44 (dm3) (1) 2 3(d) add (aqueous) potassium iodide (1) colourless to brown solution (1) 2 (a)(i) To earn the mark, you must correctly read the graph and state the time as 6 minutes. (a)(ii) To earn the first mark, you must draw a line starting from the origin with a steeper initial gradient than the original line. To earn the second mark, your drawn line must level off at 34 cm3 of gas. (b)(i) To earn the first mark, you must state that particles move faster or have more kinetic energy. To earn the second mark, you must explain that more particles have activation energy (or above), leading to more successful collisions or more energetic collisions. (b)(ii) To earn the first mark, you must state that fewer particles are exposed on the surface, or fewer particles of iron are present per unit area/cm². To earn the second mark, you must explain that collision frequency decreases, or fewer particles collide per second, or the collision rate decreases. (c) To earn the first mark, you must correctly calculate the moles of iron (3.36/56 or 0.060 mol). To earn the second mark, you must correctly calculate the volume of hydrogen as 1.44 dm3. (d) To earn the first mark, you must state adding aqueous potassium iodide. To earn the second mark, you must state the observation of a colourless to brown solution.

3 Magnesium ribbon reacts with dilute hydrochloric acid. Mg(s) + 2HCl(aq) MgCl2(aq) + H2(g) (a) The graph shows the volume of hydrogen gas produced at 20 °C as the reaction proceeds. The magnesium is in excess. volume of hydrogen gas / cm3 60 50 40 30 20 10 0 1 2 3 4 5 6 7 time / min The experiment is repeated using a lower concentration of hydrochloric acid. The volume of acid used and all other conditions are the same. Draw a line on the grid to show how the volume of hydrogen gas produced changes with time when the reaction is done with a lower concentration of hydrochloric acid. [2] (b) (i) Describe and explain, using ideas about collisions between particles, how the rate of the reaction changes when magnesium powder is used instead of magnesium ribbon. All other conditions are the same. … … … … [2] (ii) Describe and explain, using ideas about collisions between particles, how the rate of the reaction changes when the temperature of the reaction mixture is decreased. All other conditions are the same. … … … … [2] (c) Calculate the maximum volume, in dm3, of hydrogen formed when 1.68 g of magnesium react with excess dilute hydrochloric acid at room temperature and pressure. Give your answer to three significant figures. volume = … dm3 [2] (d) Magnesium is a good reducing agent. Describe a test for reducing agents. test … observations … … [2] [Total: 10]

3(a) initial gradient less steep AND starting from origin (1) line levels off at lower than 45 cm3 gas (1) 2 3(b)(i) rate of reaction increases AND one or both of: more particles exposed on surface / more (magnesium) particles per unit area / more particles per cm2 (1) collision frequency increases / collision rate increases / more collisions per second (1) 2 3(b)(ii) rate of reaction decreases AND one or both of: particles move more slowly / particles have less kinetic energy (1) fewer particles have activation energy (or above) / collisions are less successful (1) 2 3(c) mol magnesium = 1.68 24 OR 0.070 mol (1) volume of oxygen = 1.68 (dm3) (1) 2 3(d) add (aqueous acidified) potassium manganate(VII) (1) turns from purple to colourless (1) 2 (a) To earn the first mark, your drawn line must start at the origin and have a less steep initial gradient than the original line. To earn the second mark, your line must level off at a volume of hydrogen gas lower than 45 cm³. (b)(i) To earn the first mark, you must state that the rate of reaction increases. To earn the second mark, you must explain this by mentioning more particles exposed on the surface or more particles per unit area, leading to an increased collision frequency. (b)(ii) To earn the first mark, you must state that the rate of reaction decreases. To earn the second mark, you must explain this by mentioning that particles move more slowly or have less kinetic energy, resulting in fewer particles having the activation energy or collisions being less successful. (c) To earn the first mark, you must correctly calculate the moles of magnesium as 0.070 mol (or 1.68/24). To earn the second mark, you must correctly state the volume of oxygen as 1.68 dm³. (d) To earn the first mark, you must state that aqueous acidified potassium manganate(VII) is added. To earn the second mark, you must state that the solution turns from purple to colourless.

1 A student has to measure 28.2 cm3 of aqueous sodium bromide. Which piece of apparatus should the student select? B C D A

Answer: B To earn the mark, the student must identify the specific piece of apparatus (a burette) that accurately measures 28.2 cm3 of liquid.

Cambridge O Level Chemistry · 5070

O-Level Chemistry (5070) Experimental techniques and chemical analysis past paper questions

Revise O-Level Chemistry (5070) — Experimental techniques and chemical analysis 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.

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

Experimental techniques and chemical analysis in O-Level Chemistry 5070 exams, 2020–2025

Across 2020–2025, Experimental techniques and chemical analysis accounted for 291 questions worth 2,458 marks in Cambridge O Level Chemistry (5070) papers.

By year
Year	Questions	Marks
2020	55	451
2021	56	460
2022	45	429
2023	43	381
2024	45	374
2025	47	363

Most-tested subtopics

12.5 Identification of ions and gases1060 marks
12.1 Experimental design856 marks
12.2 Acid-base titrations765 marks

Appears in

Paper 1 · 93 qs
Paper 2 · 33 qs
Paper 3 · 58 qs
Paper 4 · 107 qs

All most-tested Chemistry topics

2021 Oct/Nov · Paper 2 · Q2 · 10 marks
Marking scheme
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2021 Oct/Nov · Paper 2 · Q2 · 10 marks
Marking scheme
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2021 Oct/Nov · Paper 2 · Q3 · 11 marks
Marking scheme
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2021 Oct/Nov · Paper 2 · Q3 · 10 marks
Marking scheme
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2021 May/Jun · Paper 1 · Q1 · 1 mark
Marking scheme
Mark scheme — 2021 Paper 1 Q1
Answer: B
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