Q. 23

What will happen during the electrolysis of aqueous solution of CuSO4 by using platinum electrodes?
A. Copper will deposit at cathode.

B. Copper will deposit at anode.

C. Oxygen will be released at anode.

D. Copper will dissolve at anode.

Answer :

Dissolving CuSO4 in water will lead to dissociation of CuSO4 to Cu2+ and SO42-. Water will dissociate as H+ and OH-. On electrolysis using inert platinum electrodes, the cathode and anode reactions along with their standard electrode potential are as follows:


At anode, two reactions are possible –


(i) 2H2O (l) 4H+ (aq) + O2 (g) + 4e OR 4OH (aq) 2H2O (l) + O2 (g) + 4e, EӨcell = 1.23V


(ii) 2SO42- (l) S2O82- + 2e-, EӨcell = 1.96 V


The reaction with lower electrode potential will be favoured at the anode, so O2 is released at anode.


At cathode, two reactions are possible –


(i) Cu2+ + 2e- Cu(s), EӨcell = 0.34V


(ii) H+ + e- H2(g), Eocell = 0.00 V


The reaction with higher electrode potential is favoured at the cathode, so Cu metal is deposited at the anode.


The correct options are (i) and (iii).

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