The electrolysis of copper(ii) sulfate solution using inert electrodes
4 marks · NormalCopper(II) sulfate solution is electrolysed using inert electrodes.
Write the balanced half-equation for the reaction at the cathode.
Write the balanced half-equation for the reaction at the anode.
Work this out on paper, then compare with the answer and worked solution below. With a free account you can submit written answers for marking.
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(a) Cu^{2+}(aq) + 2e^- \rightarrow Cu(s)
(b) 4OH^-(aq) \rightarrow 2H_2O(l) + O_2(g) + 4e^-
Common mistakes: Unbalanced half-equations; Wrong species at the electrodes
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Marking points
A1 (a) · 2 marks · Correct balanced half-equation for cathode: Cu^{2+}(aq) + 2e^- → Cu(s)
A2 (b) · 2 marks · Correct balanced half-equation for anode: 4OH^-(aq) → 2H_2O(l) + O_2(g) + 4e^-
Worked solution
a) At the cathode: Copper(II) ions gain electrons to form copper metal.
b) At the anode: Hydroxide ions lose electrons to form water and oxygen gas.
Alternatively, for the anode: