When a lead storage battery is recharged
A. \(Pb\) acts as cathode
B. \(PbO_2\) acts as anode
C. \(H_2SO_4\) is produced
D. 38% \(NH_4Cl\) is used as electrolyte
E. Lead storage cell has a longer life than nickel-cadmium cell
Choose the correct answer from the option given below:
Answer & explanation
Correct answer: option 3
The correct answer is Option (3) → A, B and C only
On recharging, the battery works as an electrolytic cell: an outside source drives the cell reaction backwards. Reduction takes place at the lead plate, which is now the cathode, and oxidation at the \( \ce{PbO2} \) plate, which is now the anode.
Cathode (Pb plate): \( \ce{PbSO4(s) + 2e^- -> Pb(s) + SO4^2-(aq)} \)
Anode (\( \ce{PbO2} \) plate): \( \ce{PbSO4(s) + 2H2O(l) -> PbO2(s) + SO4^2-(aq) + 4H^+(aq) + 2e^-} \)
Net reaction: \( \ce{2PbSO4(s) + 2H2O(l) -> Pb(s) + PbO2(s) + 2H2SO4(aq)} \)
A. Pb acts as cathode — Correct. On charging, \( \ce{PbSO4} \) is reduced to Pb on the lead plate, so this plate is the cathode.
B. \( \ce{PbO2} \) acts as anode — Correct. \( \ce{PbSO4} \) is oxidised to \( \ce{PbO2} \) on this plate, so it is the anode during charging.
C. \( \ce{H2SO4} \) is produced — Correct. The charging reaction gives back 2 mol of \( \ce{H2SO4} \), so the acid becomes stronger again.
D. 38% \( \ce{NH4Cl} \) is used as electrolyte — Incorrect. The electrolyte is 38% \( \ce{H2SO4} \). A moist paste of \( \ce{NH4Cl} \) and \( \ce{ZnCl2} \) is the electrolyte of the dry (Leclanché) cell.
E. Lead storage cell has a longer life than nickel-cadmium cell — Incorrect. It is the other way round: the nickel-cadmium cell has a longer life than the lead storage cell.
NCERT (2026-27 edition):
Secondary Batteries
