IGCSE Co-ordinated Sciences (Double Award) 0654 · Chemistry · 42

0654.C4.1.01 — Define electrolysis as the decomposition of an ionic compound, when molten or in aqueous solution, by the passage of an electric current: past paper questions

13 real questionsasked in 5 of the last 10 exam series2019–2025usually: What, State, Identify, Suggest, Write

Real questions on 0654.c4.1.01 — define electrolysis as the decomposition of an ionic compound, when molten or in aqueous solution, by the passage of an electric current

The newest 13 of 13 written questions. Open one to see it on the real paper.

0654/31 · October/November 2025 · Q7b(ii)[1]
State the name of each electrode. negative electrode J
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0654/31 · October/November 2025 · Q7b(iii)[1]
Identify the products at each electrode. electrode J product
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0654/31 · October/November 2025 · Q7b(iv)[1]
The molten lead bromide cools and turns solid. Suggest why the electrolysis stops.
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0654/32 · May/June 2025 · Q5a[4]
Fig. 5.1 lists five chemical processes and the descriptions of these processes. On Fig. 5.1, draw one straight line from each process to the correct description. chemical process description loss of oxygen chlorination chromatography the decomposition of an ionic compound, when molten or in aqueous solution, by the pas...
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0654/33 · May/June 2025 · Q5a[4]
Fig. 5.1 lists five chemical processes and the descriptions of these processes. On Fig. 5.1, draw one straight line from each process to the correct description. chemical process description loss of oxygen chlorination chromatography the decomposition of an ionic compound, when molten or in aqueous solution, by the pas...
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0654/42 · May/June 2025 · Q7b[1]
A student investigates the electrolysis of aqueous copper( II ) sulfate using copper electrodes. Fig. 7.1 shows the student’s experiment. d.c. – power + supply – copper anode aqueous copper(II) sulfate Fig. 7.1 Describe what the student observes at the anode. copper cathode + (b) Copper sulfate is also an ionic compoun...
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0654/42 · May/June 2025 · Q7c(i)[2]
Copper is deposited at the cathode. Write the ionic half-equation for the formation of copper, Cu, from copper ions, Cu 2+ .
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0654/42 · May/June 2025 · Q7c(ii)[1]
The ionic half-equation for the reaction at the anode is shown. Cu Cu 2+ + 2e – Explain if the reaction at the anode is oxidation or reduction.
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0654/32 · February/March 2025 · Q8d(i)[1]
State the names of the positive electrode and the negative electrode. positive electrode
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0654/21 · October/November 2024 · Q18[1]
Which statement describes what happens during electrolysis?
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0654/12 · May/June 2023 · Q18[1]
What is the name of the element and of the negative electrode?
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0654/11 · May/June 2019 · Q16[1]
What is the electrolyte that is used when a nickel spoon is electroplated with copper?
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0654/11 · May/June 2019 · Q18[1]
What is the role of iron in this reaction?
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What examiners said

This question was very well answered. There was some confusion over which process was the result of the constant random motion of particles. Electrolysis was the best-known process.
— Examiner report, May/June 2025, 0654/32 Q5(a) (Cambridge)

This question was very well answered. There was some confusion over which process was the result of the constant random motion of particles. Electrolysis was the best-known process.
— Examiner report, May/June 2025, 0654/33 Q5(a) (Cambridge)

Many of the candidates gave the observations that would occur at the cathode, rather than the anode.
— Examiner report, May/June 2025, 0654/42 Q7(b) (Cambridge)

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In the syllabus

42 0654.C4.1.01 — Define electrolysis as the decomposition of an ionic compound, when molten or in aqueous solution, by the passage of an electric current

Define electrolysis as the decomposition of an ionic compound, when molten or in aqueous solution, by the passage of an electric current
Identify in simple electrolytic cells: (a). the anode as the positive electrode (b). the cathode as the negative electrode (c). the electrolyte as the molten or aqueous substance that undergoes electrolysis
Identify the products formed at the electrodes and describe the observations made during the electrolysis of: (a). molten lead(II) bromide (b). concentrated aqueous sodium chloride (c). dilute sulfuric acid using inert electrodes made of platinum or carbon / graphite
Describe the transfer of charge during electrolysis: (a). the movement of electrons in the external circuit (b). the loss or gain of electrons at the electrodes (c). the movement of ions in the electrolyte
Identify the products formed at the electrodes and describe the observations made during the electrolysis of aqueous copper(II) sulfate using carbon / graphite electrodes and when using copper electrodes
State that metals or hydrogen are formed at the cathode and that non-metals (other than hydrogen) are formed at the anode
Predict the identity of the products at each electrode for the electrolysis of a binary compound in the molten state
Construct ionic half-equations for reactions at the cathode (showing gain of electrons as a reduction reaction)

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