1 Choose from the following compounds to answer the questions. H H H3C H3C CH3 H H O C C H H H3C H C H H3C CH3 CH3 C H3C H O C C H O H O O C H C O H H H3C C CH2 C CH3 A B C D E CH CH3 H3C H O C C O H G F CH3 Each compound may be used once, more than once or not at all. (a) State which compound: (i) has a molecule with only 14 atoms … [1] (ii) can be oxidised to form propanoic acid … [1] (iii) is an isomer of butane … [1] (iv) reacts with steam to make an alcohol … [1] (v) can be polymerised to make a polyester. … [1] (b) State which two compounds in aqueous solution turn blue litmus red. … [1] [Total: 6]

1(a)(i) E 1 1(a)(ii) A 1 1(a)(iii) E 1 1(a)(iv) D 1 1(a)(v) F 1 1(b) C and F 1 To earn marks, you must correctly identify the specific compound (A, B, C, D, E, F, or G) that matches each chemical description or property.

1 Choose from the following compounds to answer the questions. C C H H3C H3C CH3 CH3 CH3 CH3 H2C H3C H3C H2C CH2 CH2 C O C H H H H H H A O C C H H O H F D C O C H O O CH3 C O C H H H C CH3 G O H2N C O C H CH3 H H H H H H C H3C C H E B Each compound may be used once, more than once or not at all. (a) State which compound: (i) has a molecule with only 11 atoms … [1] (ii) is oxidised to form ethanoic acid … [1] (iii) is an isomer of butene … [1] (iv) reacts with hydrogen in the presence of a catalyst to make an alkane … [1] (v) contains four different elements chemically combined. … [1] (b) Identify two compounds that have a pH of less than 7 in aqueous solution. … [1] [Total: 6]

1(a)(i) C 1 1(a)(ii) A 1 1(a)(iii) B 1 1(a)(iv) D 1 1(a)(v) H 1 1(b) C and F 1 To earn marks, you must correctly identify the specific compound (A, B, C, D, E, F, G, H) that matches each description, and for part (b), identify both compounds C and F.

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.

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.

5 A compound X, when heated with an aqueous solution of compound Y, produces a gas that turns red litmus blue. 1 Y could be potassium hydroxide. 2 X is an acid. 3 X could be an ammonium salt. 4 X could be sodium nitrate. Which statements are correct? A 1, 2 and 3 B 1 and 3 only C 3 only D 2 and 4

Answer: B To earn the mark, you need to correctly identify that Y could be potassium hydroxide and X could be an ammonium salt, as these conditions lead to the production of ammonia gas which turns red litmus blue.

Cambridge O Level Chemistry · 5070

O-Level Chemistry (5070) Acids, bases and salts past paper questions

Revise O-Level Chemistry (5070) — Acids, bases and salts 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.

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

Acids, bases and salts in O-Level Chemistry 5070 exams, 2020–2025

Across 2020–2025, Acids, bases and salts accounted for 254 questions worth 1,936 marks in Cambridge O Level Chemistry (5070) papers.

By year
Year	Questions	Marks
2020	41	285
2021	46	354
2022	51	413
2023	44	306
2024	34	256
2025	38	322

Most-tested subtopics

7.1 The characteristic properties of acids and bases1523 marks
7.3 Preparation of salts394 marks
7.2 Oxides221 marks

Appears in

Paper 1 · 105 qs
Paper 2 · 64 qs
Paper 3 · 43 qs
Paper 4 · 42 qs

All most-tested Chemistry topics

2021 May/Jun · Paper 2 · Q1 · 6 marks
Marking scheme
Get Steven’s plain-English explanation
2021 May/Jun · Paper 2 · Q1 · 6 marks
Marking scheme
Get Steven’s plain-English explanation
2021 Oct/Nov · Paper 2 · Q1 · 5 marks
Marking scheme
Get Steven’s plain-English explanation
2021 Oct/Nov · Paper 2 · Q1 · 5 marks
Marking scheme
Get Steven’s plain-English explanation
2021 Oct/Nov · Paper 1 · Q5 · 1 mark
Marking scheme
Mark scheme — 2021 Paper 1 Q5
Answer: B
Get Steven’s plain-English explanation