2 (a) Fig. 2.1 shows part of Group I of the Periodic Table. lithium 7 3 Li sodium 23 11 Na potassium 39 19 K Fig. 2.1 (i) State the trend in the reactivity of the elements going down Group I. … [1] (ii) Explain why lithium does not react with helium, a Group VIII element. … … [1] (iii) Lithium is a solid and helium is a gas. Describe two differences between the structures of a solid and a gas. 1 … … 2 … … [2] (b) A piece of sodium is added to water, as shown in Fig. 2.2. sodium water Fig. 2.2 The sodium reacts with water. The reaction is exothermic. (i) State one other observation that is seen when sodium reacts with water. … [1] (ii) Complete the word equation for the reaction of sodium with water. sodium + water + [2] (c) X is a compound that reacts with dilute hydrochloric acid to form sodium chloride and water. Suggest the identity of X. … [1] (d) Concentrated aqueous sodium chloride is broken down by electrolysis. (i) State the type of chemical bond in sodium chloride. … [1] (ii) Identify the product that forms at the anode (positive electrode). … [1] [Total: 10]

2(a)(i) increasing / more reactive / faster reaction ; 1 2(a)(ii) helium / He is, unreactive / inert ; 1 2(a)(iii) any two from: (solid/lithium) particles close(r) (together) ORA ; (solid/lithium) particles regular arrangement ORA ; (solid/lithium) particles vibrate / not free-moving ORA ; 2 2(b)(i) fizzes / bubbles OR gets smaller / disappears OR moves around ; 1 2(b)(ii) sodium + water → sodium hydroxide + hydrogen in either order sodium hydroxide ; hydrogen ; 2 2(c) sodium hydroxide / NaOH OR sodium carbonate / Na2CO3 ; 1 2(d)(i) ionic ; 1 2(d)(ii) chlorine / Cl2 ; 1 (a)(i) You must state that the reactivity of Group I elements increases as you go down the group. (a)(ii) You need to explain that helium is unreactive or inert. (a)(iii) You must describe two differences between the structure of a solid and a gas, such as particle spacing (closer in solid), arrangement (regular in solid), or movement (vibrating in solid, free-moving in gas). (b)(i) You need to describe an observable change when sodium reacts with water, such as fizzing, bubbling, getting smaller, disappearing, or moving around. (b)(ii) You must correctly identify both products of the reaction: sodium hydroxide and hydrogen. (c) You need to name a suitable substance that turns universal indicator purple, such as sodium hydroxide or sodium carbonate. (d)(i) You must state that the bonding in sodium chloride is 'ionic'. (d)(ii) You need to identify 'chlorine' as the other product formed when sodium reacts with a Group VII element.

2 (a) A student separates some insoluble solid material from concentrated aqueous sodium chloride. (i) State the name of the separation method that the student uses. … [1] (ii) Identify the solute and the solvent in concentrated aqueous sodium chloride. solute … solvent … [1] (iii) State what is meant by concentrated. Use ideas about particles in your answer. … … [1] (b) The student passes an electric current through concentrated aqueous sodium chloride, as shown in Fig. 2.1. concentrated aqueous sodium chloride inert carbon electrodes low voltage d.c. supply – + Fig. 2.1 (i) State the name of this process. … [1] (ii) State the name of the positive electrode. … [1] (iii) Identify the product that forms at the negative electrode. … [1] (c) Sodium is a metal, and chlorine is a diatomic non-metal. When sodium and chlorine are heated together, sodium chloride is formed. (i) State what is meant by diatomic. … … [1] (ii) State the type of chemical bonding present in sodium chloride. … [1] (iii) Describe a chemical test for the presence of chloride ions in aqueous sodium chloride. State the observation for a positive result. test … … observation … … [2] [Total: 10]

2(a)(i) filtration / filter(ing) ; 1 2(a)(ii) solute: sodium chloride / NaCl AND solvent: water / H2O ; 1 2(a)(iii) there are many / more solute particles in (a solution) ; 1 2(b)(i) electrolysis ; 1 2(b)(ii) anode ; 1 2(b)(iii) hydrogen ; 1 2(c)(i) (contains) only two atoms joined (in a molecule) ; 1 2(c)(ii) ionic ; 1 2(c)(iii) test: (aqueous) silver nitrate AND (dilute) nitric acid ; result: white precipitate ; 2

2 (a) A student separates some insoluble solid material from concentrated aqueous sodium chloride. (i) State the name of the separation method that the student uses. … [1] (ii) Identify the solute and the solvent in concentrated aqueous sodium chloride. solute … solvent … [1] (iii) State what is meant by concentrated. Use ideas about particles in your answer. … … [1] (b) The student passes an electric current through concentrated aqueous sodium chloride, as shown in Fig. 2.1. concentrated aqueous sodium chloride inert carbon electrodes low voltage d.c. supply – + Fig. 2.1 (i) State the name of this process. … [1] (ii) State the name of the positive electrode. … [1] (iii) Identify the product that forms at the negative electrode. … [1] (c) Sodium is a metal, and chlorine is a diatomic non-metal. When sodium and chlorine are heated together, sodium chloride is formed. (i) State what is meant by diatomic. … … [1] (ii) State the type of chemical bonding present in sodium chloride. … [1] (iii) Describe a chemical test for the presence of chloride ions in aqueous sodium chloride. State the observation for a positive result. test … … observation … … [2] [Total: 10]

2(a)(i) filtration / filter(ing) ; 1 2(a)(ii) solute: sodium chloride / NaCl AND solvent: water / H2O ; 1 2(a)(iii) there are many / more solute particles in (a solution) ; 1 2(b)(i) electrolysis ; 1 2(b)(ii) anode ; 1 2(b)(iii) hydrogen ; 1 2(c)(i) (contains) only two atoms joined (in a molecule) ; 1 2(c)(ii) ionic ; 1 2(c)(iii) test: (aqueous) silver nitrate AND (dilute) nitric acid ; result: white precipitate ; 2

8 (a) An atom of lead is represented by the symbol shown. 207 82 Pb (i) Deduce the number of electrons and number of neutrons in this atom. electrons … neutrons … [2] (ii) The proton number (atomic number) of lead is 82. Define the term proton number. … … [1] (iii) State the charges of protons, neutrons and electrons. protons … neutrons … electrons … [1] (b) Lead is extracted from molten lead(II) bromide using the apparatus shown in Fig. 8.1. molten lead(II) bromide – + low voltage d.c. supply Fig. 8.1 (i) Name the process shown in Fig. 8.1. … [1] (ii) State the name of the electrode at which lead forms. … [1] (c) Lead is extracted from lead(II) oxide, PbO, by heating with carbon. Carbon dioxide is also made in this endothermic reaction. (i) Describe what is meant by an endothermic reaction. … … [1] (ii) Complete the word equation for this reaction. lead + + [1] (iii) Circle the word to show whether lead(II) oxide is oxidised or reduced in this reaction. Explain your answer. oxidised reduced explanation … … [1] (d) A teacher has a different compound of lead. When this compound of lead reacts with dilute hydrochloric acid, carbon dioxide is formed. Suggest the name of this compound of lead. … [1] [Total: 10]

8(a)(i) (electrons) 82 ; (neutrons) 125 ; 2 8(a)(ii) the number of protons in the nucleus of an atom ; 1 8(a)(iii) (protons) +1 (neutrons) no charge (electrons) -1 ; all three needed for one mark 1 8(b)(i) electrolysis ; 1 8(b)(ii) cathode ; 1 8(c)(i) takes in, heat / energy ; 1 8(c)(ii) ; 1 8(c)(iii) reduced (circled) AND (explanation) loses oxygen ; 1 8(d) lead carbonate / PbCO3 ; 1 To earn marks, you must correctly state 82 electrons and 125 neutrons. You need to define proton number as the number of protons in the nucleus of an atom. For charges, you must state +1 for protons, no charge for neutrons, and -1 for electrons, with all three correct for the mark. You must name the process as 'electrolysis' and the electrode where lead forms as the 'cathode'. For the reaction with carbon, you need to state that it 'takes in heat/energy', draw the correct energy profile diagram, and explain that lead(II) oxide is 'reduced' because it 'loses oxygen'. Finally, you must name 'lead carbonate' or 'PbCO3' as the compound that causes acid rain.

Cambridge IGCSE Combined Science · 0653

IGCSE Combined Science (0653) Electrochemistry past paper questions

Revise IGCSE Combined Science (0653) — Electrochemistry 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.

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

Electrochemistry in IGCSE Combined Science 0653 exams, 2020–2025

Across 2020–2025, Electrochemistry accounted for 105 questions worth 417 marks in Cambridge IGCSE Combined Science (0653) papers.

By year
Year	Questions	Marks
2020	19	86
2021	16	69
2022	20	73
2023	17	85
2024	22	62
2025	11	42

Most-tested subtopics

C4.1 Electrolysis354 marks

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Paper 1 · 32 qs
Paper 2 · 31 qs
Paper 3 · 20 qs
Paper 4 · 22 qs

All most-tested Combined Science topics

2021 May/Jun · Paper 3 · Q2 · 10 marks
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2021 Oct/Nov · Paper 3 · Q2 · 10 marks
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2021 Oct/Nov · Paper 3 · Q2 · 10 marks
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2021 Feb/Mar · Paper 3 · Q8 · 10 marks
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2021 Feb/Mar · Paper 1 · Q16 · 1 mark
Marking scheme
Mark scheme — 2021 Paper 1 Q16
Answer: D
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