Chemistry
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)
Answer
(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
Related Questions
Give reasons why:
(i) Sodium Chloride will conduct electricity only in fused or aq. soln. state.
(ii) In the electroplating of an article with silver, the electrolyte sodium argentocyanide soln. is preferred over silver nitrate solution.
(iii) Although copper is a good conductor of electricity, it is a non-electrolyte.
The particles present in strong electrolytes are:
Select the correct answer from A, B, C and D:
A: only molecules
B: mainly ions
C: ions and molecules
D: only atomsName:
(i) the product formed at the anode – during electrolysis of acidified water using platinum electrodes.
(ii) the metallic ions that should be present – in the electrolyte when an article made of copper is to be electroplated with silver.
During purification of copper – State:
(i) The anode used
(ii) The electrolyte used.
Write the equation taking place at the anode in the above.