8 Silver is a transition element with proton number 47. (a) Use the Periodic Table to state the number of occupied electron shells in an atom of silver. … [1] (b) Describe, with the aid of a diagram, the metallic bonding in silver. … … … … [3] (c) Give two physical properties of silver that are only characteristic of transition elements but not of all metals. 1. … 2. … [1] (d) Silver nitrate is a white crystalline soluble salt. Name a suitable combination of an acid and an insoluble base which is used to prepare silver nitrate. acid … base … [1] (e) Aqueous silver nitrate, AgNO3(aq), is electrolysed using inert electrodes. The products of the electrolysis are silver and oxygen. (i) Silver ions are reduced at the cathode to make silver atoms. Construct the ionic equation for this reduction. … [1] (ii) Hydroxide ions are oxidised at the anode to make both oxygen molecules and water molecules. Construct the ionic equation for this oxidation. … [1] (iii) Explain why solid silver nitrate cannot be electrolysed. … … [1] (f) Acidified aqueous silver nitrate reacts with aqueous sodium iodide. State the observations for this reaction. … [1] [Total: 10]

8(a) five 1 8(b) closely packed positive ions (1) delocalised electrons / sea of electrons (1) strong electrostatic attraction between the (positive) ions and the electrons (1) 3 8(c) high melting point / high boiling point AND high density 1 8(d) silver oxide / silver hydroxide AND nitric acid 1 8(e)(i) Ag+ + e− → Ag 1 8(e)(ii) 4OH− → O2 + 2H2O + 4e− / 4OH− − 4e− → O2 + 2H2O 1 8(e)(iii) ions cannot move / no mobile ions 1 8(f) (light) yellow ppt. 1 positive ion delocalised electrons

9 This question is about ammonia and nitrates. (a) State the source of the hydrogen and nitrogen used in the manufacture of ammonia by the Haber process. source of hydrogen … source of nitrogen … [2] (b) Ammonia is formed when aqueous ammonium sulfate is heated with sodium hydroxide. (NH4)2SO4 + 2NaOH 2NH3 + Na2SO4 + 2H2O A student adds 4.50 g of sodium hydroxide to 50.0 cm3 of 1.25 mol / dm3 aqueous ammonium sulfate. Show by calculation that the ammonium sulfate is in excess. [3] (c) When dilute sodium hydroxide is electrolysed, the hydroxide ions are converted to oxygen and water at the anode. Construct the ionic equation for the reaction taking place at the anode. … [1] (d) The first stage in the test for nitrate ions is to heat aluminium and sodium hydroxide with a solution containing nitrate ions. State the type of chemical reaction which occurs when a solution containing nitrate ions is heated with aluminium and sodium hydroxide. … [1] (e) Nitrates from fertilisers cause eutrophication when they are leached from soils into rivers. Describe the process of eutrophication. … … … … … [3] [Total: 10]

9(a) hydrogen: (cracking) hydrocarbons (1) nitrogen: air (1) 2 9(b) NaOH = 4.5 40 OR 0.1125 (mol) (1) (NH4)2SO4 = 50 1000 × 1.25 OR 0.0625 (mol) (1) ((NH4)2SO4 because 0.0625 × 2) = 0.125 OR ((NH4)2SO4 because 0.1125 ÷ 2) = 0.056 (1) 3 9(c) 4OH– → O2 + 2H2O + 4e– / 4OH– – 4e– → O2 + 2H2O (1) 1 9(d) reduction 1 9(e) Any three from: (nitrates) increase growth of algae / (nitrates) increase growth of water plants / algal bloom (1) plants (on surface) block sunlight and plants die (1) bacteria feed on dead plants and use up oxygen (1) (without oxygen) fish die / (without oxygen) water organisms die (1) 3

9 This question is about sulfuric acid and sulfates. (a) (i) Sulfur is one of the raw materials used in the Contact process to make sulfuric acid. Name two other raw materials used to make sulfuric acid. … and … [1] (ii) Name the catalyst used in the Contact process. … [1] (b) The electrolysis of dilute sulfuric acid using inert electrodes produces oxygen at the anode. (i) Define the term electrolysis. … … … [2] (ii) Construct the equation for the reaction taking place at the cathode. … [1] (c) Dilute sulfuric acid reacts with sodium hydroxide. H2SO4 + 2NaOH Na2SO4 + 2H2O A student adds 0.76 g of solid sodium hydroxide to 45 cm3 of 0.20 mol / dm3 sulfuric acid. Show by calculation that the sodium hydroxide is in excess. [3] (d) Aqueous sodium hydroxide is warmed with ammonium sulfate. State the names of the three products formed in this reaction. 1 … 2 … 3 … [2] [Total: 10]

9(a)(i) air AND water 1 9(a)(ii) vanadium(V) oxide 1 9(b)(i) decomposition of an ionic compound / decomposition of an electrolyte (1) using electricity (1) 2 9(b)(ii) 2H+ + 2e– → H2 1 9(c) mol H2SO4 = 45 1000 × 0.20 OR 0.009 (1) mol sodium hydroxide = 0.76 40 OR 0.019 mol (1) (sodium hydroxide because 0.019 is greater than) 2 × 0.009 OR (sodium hydroxide because 0.009 is less than) 0.019 / 2 (1) 3 9(c) ammonia AND sodium sulfate AND water (2) if 2 marks not scored 1 mark for any two of ammonia, sodium sulfate or water 2

2 Part of the reactivity series is shown. calcium aluminium manganese zinc more reactive less reactive (a) Predict the names of the products formed when manganese reacts with dilute hydrochloric acid. … … [1] (b) A sample of manganese(II) carbonate, MnCO3, is heated strongly. Construct the equation for this reaction. … [1] (c) Powdered manganese is added to aqueous zinc sulfate to form aqueous manganese(II) sulfate, MnSO4. Construct an ionic equation, with state symbols, for this reaction. … [2] (d) Zinc powder, a reducing agent, is added to acidified aqueous potassium manganate(VII). Describe the colour change during this reaction. … [1] (e) Aluminium is extracted by the electrolysis of aluminium oxide dissolved in molten cryolite. (i) Write the electrode equation for the formation of aluminium atoms at the cathode. … [1] (ii) Write the electrode equation for the formation of oxygen molecules at the anode. … [1] (f) State one advantage of recycling aluminium. … [1] [Total: 8]

2(a) reacts to give hydrogen and manganese chloride (1) 1 2(b) MnCO3MnO + CO2 (1) 1 2(c) Mn(s) + Zn2+(aq)  Mn2+(aq) + Zn(s) balanced (1) state symbols – dependent on correct formulae (1) 2 2(d) purple to colourless (1) 1 2(e)(i) Al3+ + 3e−  Al (1) 1 2(e)(ii) 2O2−  O2 + 4e− / 2O2− − 4e−  O2(1) 1 2(f) saves natural resources / less environmental damage due to mining / saves energy (1) 1 (a) To earn the mark, you must state both 'hydrogen' and 'manganese chloride' as the products. (b) To earn the mark, you must write the balanced chemical equation for the decomposition of manganese(II) carbonate. (c) To earn the first mark, you must write the correct balanced ionic equation. To earn the second mark, you must include the correct state symbols for all species, dependent on the correct formulae. (d) To earn the mark, you must state the colour change from 'purple to colourless'. (e)(i) To earn the mark, you must write the correct electrode equation for the formation of aluminium. (e)(ii) To earn the mark, you must write the correct electrode equation for the formation of oxygen. (f) To earn the mark, you must state one valid environmental or resource-saving benefit of recycling aluminium.

13 An aqueous mixture of copper(II) nitrate and silver nitrate is electrolysed with pure copper electrodes. Which half-equation correctly describes the change occurring at the anode? A Cu  Cu2+ + 2e– B Cu2+ + 2e–  Cu C Ag  Ag+ + e– D Ag+ + e–  Ag

Answer: A To earn the mark, a student must correctly identify the half-equation that describes the oxidation of copper at the anode during the electrolysis.

Cambridge O Level Chemistry · 5070

O-Level Chemistry (5070) Electrochemistry past paper questions

Revise O-Level Chemistry (5070) — 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.

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

Electrochemistry in O-Level Chemistry 5070 exams, 2020–2025

Across 2020–2025, Electrochemistry accounted for 93 questions worth 380 marks in Cambridge O Level Chemistry (5070) papers.

By year
Year	Questions	Marks
2020	19	89
2021	14	41
2022	19	106
2023	12	51
2024	16	47
2025	13	46

Most-tested subtopics

4.1 Electrolysis292 marks
4.2 Hydrogen-oxygen fuel cells41 marks

Appears in

Paper 1 · 56 qs
Paper 2 · 30 qs
Paper 4 · 7 qs

All most-tested Chemistry topics

2021 May/Jun · Paper 2 · Q8 · 10 marks
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2021 Oct/Nov · Paper 2 · Q9 · 10 marks
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2021 Oct/Nov · Paper 2 · Q9 · 10 marks
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2020 May/Jun · Paper 2 · Q2 · 8 marks
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2021 May/Jun · Paper 1 · Q13 · 1 mark
Marking scheme
Mark scheme — 2021 Paper 1 Q13
Answer: A
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