The electrolysis of copper(ii) sulfate solution using inert electrodes
3 marks · NormalCopper is deposited at the cathode during the electrolysis of copper(II) sulfate solution with inert electrodes.
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Copper is deposited at the cathode because copper ions are reduced more easily than hydrogen ions, since copper is below hydrogen in the reactivity series.
Also accept: Copper ions are discharged in preference to hydrogen due to its position in the reactivity series
Common mistakes: Saying copper forms because it 'has to'; Confusion with anode/cathode
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Marking points
M1 · 1 mark · States that both Cu^{2+} ions and H^+ ions are attracted to the cathode
M2 · 1 mark · Mentions that copper is below hydrogen in the reactivity series (less reactive)
A1 · 1 mark · States that copper ions are preferentially reduced (or copper deposited) at the cathode
Worked solution
At the cathode, both copper(II) ions (Cu^{2+}) and hydrogen ions (H^+) from water move towards the electrode.
Copper is below hydrogen in the reactivity series, so it is more easily reduced than hydrogen ions.
Therefore, copper ions gain electrons to form copper metal, so copper is deposited at the cathode.