The electrolysis of some other solutions using inert electrodes

2 marks · Normal

State the products formed at the cathode and at the anode when dilute sodium sulfate solution is electrolysed using inert electrodes.

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Cathode: hydrogen gas; Anode: oxygen gas

Also accept: Cathode: H2; Anode: O2; Hydrogen (at cathode), Oxygen (at anode)

Common mistakes: Saying sodium or sulfate are discharged

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Marking points

B1 · 1 mark · Identifies hydrogen gas as the product at the cathode.

B2 · 1 mark · Identifies oxygen gas as the product at the anode.

Worked solution

At the cathode, hydrogen ions are discharged to give hydrogen gas: 2H+(aq) + 2e- → H2(g)

At the anode, hydroxide ions are discharged to give oxygen gas: 4OH-(aq) → O2(g) + 2H2O(l) + 4e-

So the products are: Cathode — hydrogen gas; Anode — oxygen gas.