The electrolysis of copper(ii) sulfate solution using inert electrodes
3 marks · EasyExplain why oxygen is produced at the anode and not sulfate ions are discharged during the electrolysis of copper(II) sulfate solution with inert electrodes.
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Sulfate ions are harder to oxidise compared to hydroxide ions, so hydroxide ions are discharged at the anode to form oxygen gas.
Must show: Sulfate ions are not easily oxidised, Hydroxide ions are discharged instead, Oxygen gas is formed at the anode
Also accept: Sulfate ions stay in solution; hydroxide ions are oxidised to produce oxygen gas.
Common mistakes: Saying sulfate ions oxidised; Not comparing ions
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Marking points
M1 · 1 mark · States sulfate ions are difficult to oxidise (or not easily discharged).
M1 · 1 mark · States hydroxide ions are more easily oxidised/discharged.
A1 · 1 mark · States oxygen is produced (from hydroxide ions).
Worked solution
Sulfate ions are not easily oxidised at the anode. Hydroxide ions from the water are discharged instead, losing electrons more easily. This forms oxygen gas at the anode.