Electrochemistry — IGCSE Science - Combined (0653) questions by topic
Explaining what happens at each electrode during electrolysis, and identifying the elements and compounds involved, define this topic: naming inert electrode materials, working out which ions are attracted to which electrode, and describing why lead bromide must be molten before conducting. State, complete and identify are the dominant command words, each wanting a specific named substance or ion rather than a general electrolysis description.
Its 16 real questions, drawn from 2023 to 2025 papers, are worth 1 to 10 marks, so single-word recall sits alongside multi-part explanation. Practising with instant marking is useful here because ion-charge errors, such as treating hydrogen or sodium ions as negative, are easy to repeat unless flagged and corrected straight away.
What examiners look for
- A frequent misconception is thinking the charges on hydrogen and sodium ions are negative, when both are positive.
- Simply stating that ions are attracted to the positive electrode 'because they were negative' is not accepted as an explanation.
- Vague general properties of metals are often given where a property specific to transition elements, or specific to an electrode's function, is required.
- A common misconception has electrons flowing through the electrolyte itself, when this only applies to the external circuit.
- Strong answers identify water as the source of the hydroxide ion with correct ion formulae, and understand that lead bromide must be molten to provide mobile ions before electrolysis can occur.
May–June 2025, Paper 11
The diagram shows electrolysis apparatus. A cell (labelled A) is connected to two electrodes dipping into a liquid electrolyte. The electrode connected to the positive terminal is…
Answer this question and get it marked →May–June 2025, Paper 12
What is produced at the anode during the electrolysis of molten lead(II) bromide? A bromide ions B bromine C lead D lead(II) ions
Answer this question and get it marked →May–June 2025, Paper 13
The diagram shows the apparatus for electrolysis. Two electrodes dip into a liquid in a beaker; the left electrode (W) is connected to the negative terminal and the right…
Answer this question and get it marked →May–June 2025, Paper 21
Which row shows what forms at the electrodes during electrolysis of an aqueous compound? anode cathode --- --- --- A metal non-metal B non-metal metal C hydrogen metal D hydrogen…
Answer this question and get it marked →May–June 2025, Paper 22
Which row shows an electrolyte and the products of electrolysis for this electrolyte? electrolyte products --- --- --- A concentrated aqueous sodium chloride sodium and chlorine B…
Answer this question and get it marked →May–June 2025, Paper 23
Apparatus used to electrolyse molten lead(II) bromide is shown. The diagram shows a d.c. power supply connected to two electrodes dipping into a container of molten liquid. The…
Answer this question and get it marked →October–November 2024, Paper 32
Fig. 8.1 shows apparatus for the electrolysis of dilute sulfuric acid using inert electrodes (a glass container of dilute sulfuric acid with two electrodes connected to a battery,…
Answer this question and get it marked →October–November 2024, Paper 33
Fig. 8.1 shows apparatus for the electrolysis of dilute sulfuric acid using inert electrodes (a glass container of dilute sulfuric acid with two electrodes connected to a battery,…
Answer this question and get it marked →October–November 2024, Paper 42
(a) State the names of two elements that are used to make inert electrodes for electrolysis.
Answer this question and get it marked →October–November 2024, Paper 43
Dilute sulfuric acid is electrolysed using inert electrodes as shown in Fig. 5.1 (positive electrode and negative electrode in dilute sulfuric acid, connected to a d.c. power…
Answer this question and get it marked →May–June 2023, Paper 32
A student investigates sodium chloride, NaCl, by making a concentrated aqueous solution and electrolysing it (Fig. 2.1: a low voltage d.c. supply with a negative and a positive…
Answer this question and get it marked →May–June 2023, Paper 41
An electric current is passed through concentrated aqueous sodium chloride using inert electrodes (Fig. 2.1: chlorine at the positive electrode, hydrogen at the negative…
Answer this question and get it marked →May–June 2023, Paper 42
Concentrated aqueous sodium chloride is electrolysed using platinum electrodes (Fig. 2.1, gas X at the positive electrode). At the start of the electrolysis, the aqueous solution…
Answer this question and get it marked →May–June 2023, Paper 43
Dilute sulfuric acid is electrolysed using carbon electrodes (Fig. 2.1); bubbles of gas form at both electrodes. The ionic equation for the reaction at the positive electrode is…
Answer this question and get it marked →October–November 2023, Paper 41
A student uses inert electrodes to investigate the electrolysis of lead(II) bromide, as shown in Fig. 2.1 (a positive and a negative electrode dipping into lead(II) bromide that…
Answer this question and get it marked →October–November 2023, Paper 43
Fig. 2.1 shows the electrolysis of concentrated aqueous sodium chloride using platinum electrodes (chlorine gas forms at the positive electrode). Table 2.1 gives some information…
Answer this question and get it marked →Other IGCSE Science - Combined topics
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- Motion, forces and energy (53)
- Electricity and magnetism (38)
- Waves (32)
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- Acids, bases and salts (22)
- Organisms and their environment (21)
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- Reproduction (20)
- Thermal physics (20)
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- The Periodic Table (18)