The electrolysis of copper(ii) sulfate solution using inert electrodes
4 marks · NormalThe following table shows the observations at the electrodes during electrolysis of copper(II) sulfate solution with inert electrodes.
| Electrode | Observation |
|---|---|
| Cathode | Pink/brown coating forms |
| Anode | Gas bubbles produced |
Name the substance forming the pink/brown coating at the cathode.
Name the gas produced at the anode.
Suggest a simple test to confirm the identity of the gas collected 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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(b) Copper (Cu)
(c) Oxygen (O2)
(d) Insert a glowing splint into the gas; if it relights, the gas is oxygen.
Common mistakes: Confusing hydrogen with oxygen
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Marking points
B1 (b) · 1 mark · Names copper (Cu) as the pink/brown cathode coating
B2 (c) · 1 mark · Names oxygen (O2) as the gas at the anode
M1 (d) · 1 mark · Suggests using a glowing splint as the test for oxygen
A1 (d) · 1 mark · States the result: splint relights (or burns brighter)
Worked solution
b) The pink/brown coating at the cathode is copper metal (Cu).
c) The gas given off at the anode is oxygen (O_2).
d) To test for oxygen, hold a glowing splint in the gas. If the splint relights, the gas is oxygen.