1 The diagram shows part of the Periodic Table. I II III IV V VI VII VIII Mg Al Ar Cl Br I C N O F Ca Cr Fe Cu Zn Pt K Answer the following questions using only the symbols of the elements in the diagram. Each symbol may be used once, more than once or not at all. Give the symbol of the element that: (a) is extracted from bauxite … [1] (b) forms 21% of clean, dry air … [1] (c) forms an oxide which contributes to acid rain … [1] (d) forms an aqueous ion that gives a red-brown precipitate on addition of aqueous sodium hydroxide … [1] (e) has an atom with a complete outer electron shell. … [1] [Total: 5]

1(a) Al 1 1(b) O 1 1(c) N 1 1(d) Fe 1 1(e) Ar 1 To earn the mark, you must correctly identify the specific element symbol for each description.

1 (a) A list of formulae is shown. Al Cl 3 CaCO3 CO CO2 CoCl 2 CuSO4 MgCl 2 N2 NaCl NH3 O2 SO2 Answer the following questions using these formulae. Each formula may be used once, more than once or not at all. State which formula represents: (i) a compound that changes colour from white to blue when water is added … [1] (ii) a compound that is used to make cement … [1] (iii) an element that forms 78% of clean, dry air … [1] (iv) a compound that contains an ion with a single positive charge … [1] (v) a compound that dissolves in water to form an alkaline solution. … [1] (b) Complete the dot-and-cross diagram to show the electron arrangement in a molecule of ammonia. N H H H [2] (c) State whether magnesium oxide is a basic oxide or an acidic oxide. Give a reason for your answer. … … [1] [Total: 8]

1(a)(i) CuSO4 1 1(a)(ii) CaCO3 1 1(a)(iii) N2 1 1(a)(iv) NaCl 1 1(a)(v) NH3 1 1(b) bonding pair of electrons between the N atom and each of the H atoms with no other electrons on the H atom (1) 2 non-bonding electrons on N atom (1) 2 1(c) basic oxide AND magnesium is a metal / metal oxides are basic (1) 1 (a)(i) To earn this mark, you must correctly identify CuSO4 as the compound that changes color from white to blue when water is added. (a)(ii) To earn this mark, you must correctly identify CaCO3 as the compound used to make cement. (a)(iii) To earn this mark, you must correctly identify N2 as the element that forms 78% of clean, dry air. (a)(iv) To earn this mark, you must correctly identify NaCl as the compound that contains an ion with a single positive charge. (a)(v) To earn this mark, you must correctly identify NH3 as the compound that dissolves in water to form an alkaline solution. (b) To earn the first mark, you must show a bonding pair of electrons between the N atom and each H atom, with no other electrons on the H atoms. To earn the second mark, you must show two non-bonding electrons on the N atom. (c) To earn this mark, you must state that magnesium oxide is a basic oxide AND provide the reason that magnesium is a metal or that metal oxides are basic.

1 (a) A list of formulae is shown. CaCO3 CaO Cl 2 CH4 C2H5OH C2H6 CuSO4 H2 H2O MgO NaCl SO2 Answer the following questions using these formulae. Each formula may be used once, more than once or not at all. State which formula represents: (i) a compound that is the main constituent of natural gas … [1] (ii) an element that is used in water treatment … [1] (iii) an element that bleaches damp litmus paper … [1] (iv) a compound that contains an ion with a single negative charge … [1] (v) a hydrocarbon that is formed by the decomposition of vegetation. … [1] (b) Complete the dot-and-cross diagram to show the electron arrangement in a molecule of water. H H O [2] (c) State whether calcium oxide is a basic oxide or an acidic oxide. Give a reason for your answer. … … [1] [Total: 8]

1(a)(i) CH4 1 1(a)(ii) Cl 2 1 1(a)(iii) Cl 2 1 1(a)(iv) NaCl 1 1(a)(v) CH4 1 1(b) bonding pair of electrons between each H and O atom and no other electrons on H atoms (1) four non-bonding electrons on the oxygen atom (1) 2 1(c) basic (oxide) AND calcium is a metal / metal oxides are basic (1) 1 (a) To earn marks, you must correctly identify the chemical formula for each description from the provided list. (b) To earn marks, you must draw a dot-and-cross diagram showing one bonding pair of electrons between each hydrogen and oxygen atom, with no other electrons on the hydrogen atoms, and four non-bonding electrons on the oxygen atom. (c) To earn the mark, you must state that calcium oxide is a basic oxide and provide the reason that calcium is a metal or that metal oxides are basic.

1 (a) A list of formulae is shown. Br2 CO CO2 CH4 C2H6 HCl KBr LiCl MgCl 2 O2 SO2 Answer the following questions using these formulae. Each formula may be used once, more than once or not at all. State which formula represents: (i) a compound that gives a red colour in a flame test … [1] (ii) a compound containing an ion with a 2+ charge … [1] (iii) a compound that is a product of respiration … [1] (iv) a compound used as a food preservative … [1] (v) an element that is used in the production of steel. … [1] (b) Complete the dot-and-cross diagram to show the electron arrangement in a molecule of hydrogen chloride. Show outer shell electrons only. Cl H [2] (c) State whether carbon dioxide is a basic oxide or an acidic oxide. Give a reason for your answer. … … [1] [Total: 8]

1(a)(i) LiCl 1 1(a)(ii) MgCl2 1 1(a)(iii) CO2 1 1(a)(iv) SO2 1 1(a)(v) O2 1 1(b) bonding pair of electrons between the Cl atom and H atom and no other electrons on hydrogen atom (1) 6 non-bonding electrons on Cl atom (1) 2 1(c) acidic (oxide) AND carbon is a non-metal / non-metal oxides are acidic (1) 1 (a) To earn marks, you must correctly identify the specific chemical formula from the provided list for each description. (b) For the first mark, draw a single bonding pair of electrons between H and Cl, ensuring no other electrons are on the hydrogen atom. For the second mark, show six non-bonding electrons (three lone pairs) on the chlorine atom. (c) You must state that carbon dioxide is an acidic oxide AND provide the reason that carbon is a non-metal or that non-metal oxides are acidic.

11 The temperature decreases when aqueous ethanoic acid reacts with solid sodium carbonate to form a salt. Which type of reaction and energy change occur? type of reaction energy change A neutralisation endothermic B neutralisation exothermic C redox endothermic D redox exothermic

Answer: A To earn this mark, a student must correctly identify that the reaction between an acid and a carbonate is neutralisation and that a decrease in temperature indicates an endothermic energy change.

Cambridge IGCSE Chemistry · 0620

IGCSE Chemistry (0620) Acids, bases and salts past paper questions

These questions cover acid and base reactions, pH, and the preparation of salts.

941 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 IGCSE Chemistry 0620 exams, 2020–2025

Across 2020–2025, Acids, bases and salts accounted for 872 questions worth 4,789 marks in Cambridge IGCSE Chemistry (0620) papers.

By year
Year	Questions	Marks
2020	160	889
2021	152	860
2022	155	772
2023	145	842
2024	140	743
2025	120	683

Most-tested subtopics

7.1 Characteristic properties of acids and bases2009 marks
7.4 Identification of ions and gases1915 marks
7.3 Preparation of salts977 marks

Appears in

Paper 1 · 267 qs
Paper 2 · 233 qs
Paper 3 · 146 qs
Paper 4 · 83 qs
Paper 5 · 61 qs
Paper 6 · 82 qs

All most-tested Chemistry topics

2021 Feb/Mar · Paper 3 · Q1 · 5 marks
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2021 Oct/Nov · Paper 3 · Q1 · 8 marks
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2021 Oct/Nov · Paper 3 · Q1 · 8 marks
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2021 Oct/Nov · Paper 3 · Q1 · 8 marks
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2021 Oct/Nov · Paper 1 · Q11 · 1 mark
Marking scheme
Mark scheme — 2021 Paper 1 Q11
Answer: A
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