The electrolysis of aqueous solutions
4 marks · NormalConcentrated sodium chloride solution is electrolysed using carbon electrodes.
Name the product formed at the cathode.
Name the product formed at the anode.
Write a word or balanced symbol equation for the half-equation at the cathode.
Write a word or balanced symbol equation for the half-equation 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) Hydrogen
(b) Chlorine
(c) 2H2O(l) + 2e^- → H2(g) + 2OH^-(aq)
(d) 2Cl^-(aq) → Cl2(g) + 2e^-
Common mistakes: Incorrect product at electrodes; Wrong half-equation direction
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Marking points
B1 (a) · 1 mark · Correctly names hydrogen as the cathode product
B2 (b) · 1 mark · Correctly names chlorine as the anode product
B3 (c) · 1 mark · Correct half-equation at the cathode (accept word or symbol)
B4 (d) · 1 mark · Correct half-equation at the anode (accept word or symbol)
Worked solution
a. The product at the cathode is hydrogen.
b. The product at the anode is chlorine.
c. Cathode half-equation: 2H2O(l) + 2e^- → H2(g) + 2OH^-(aq)
d. Anode half-equation: 2Cl^-(aq) → Cl2(g) + 2e^-