1(iv)
With respect to the electrolysis of copper (II) sulphate solution using copper electrodes, which statement is correct?
- (a)Copper metal is deposited at the negative electrode.
- (b)Oxygen gas is produced at the positive electrode.
- (c)The positive electrode increases in mass.
- (d)The negative electrode decreases in mass.
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Copper metal is deposited at the negative electrode.
Reason — During electrolysis of copper(II) sulphate solution using copper electrodes:
- At the cathode (negative electrode): Cu2+ + 2e- ⟶ Cu, so copper is deposited here and the cathode increases in mass.
- At the anode (positive electrode): Cu - 2e- ⟶ Cu2+, so copper of the anode dissolves and the anode decreases in mass.
No oxygen gas is produced because the copper is preferentially oxidised over the OH- ions.