Write equations for the reactions taking place at the two electrodes during the electrolysis of:
(i) Acidified CuSO4 solution with copper electrodes.
(ii) Molten PbBr2 with inert electrodes. (mention clearly the name of the electrode in each case)

(i) Electrode — Cathode : Copper, Anode : Copper

Dissociation of aq. CuSO4 :

CuSO4 ⇌ Cu2+ + SO42-

H2O ⇌ H1+ + OH1-

H2SO4 ⇌ 2H1+ + SO42-

Reaction at cathode [pure thin sheet of Cu]:
Cu2+ + 2e ⟶ Cu [Cu deposited on thin sheet]

Reaction at anode [impure block of active Cu]:
Cu – 2e ⟶ Cu2+ [product nil – Cu2+ ions]

(ii) Electrode — Cathode : Iron or Graphite, Anode : Graphite

Dissociation of molten PbBr2 : PbBr2 ⇌ Pb2+ (cathode) + 2Br1- (anode)

Reaction at cathode:
Pb2+ + 2e ⟶ Pb [product lead metal]

Reaction at anode:
Br1- – 1e⟶ Br
Br + Br ⟶ Br2

Leave a Reply