Which of the following reaction occurs at anode during discharging of…

The correct answer is Option (2) → Pb(s) + SO₄²⁻(aq) → PbSO₄(s) + 2e⁻

While the lead storage battery is discharging (in use) it works as a galvanic cell, and oxidation takes place at the anode: the lead anode is oxidised from 0 to +2 and combines with sulphate ions from the 38% \( \ce{H2SO4} \) electrolyte, releasing two electrons.

    \( \displaystyle \text{Anode: }\ce{Pb(s) + SO4^2-(aq) -> PbSO4(s) + 2e^-} \)

Why the other options are incorrect

• Option (1) PbO₂(s) + SO₄²⁻(aq) + 4H⁺(aq) + 2e⁻ → PbSO₄(s) + 2H₂O(l) — Incorrect. This is a reduction (electrons are gained, Pb goes from +4 to +2); it takes place at the cathode.

• Option (3) PbSO₄ + 2e⁻ → Pb(s) + SO₄²⁻(aq) — Incorrect. This is the reverse of the anode reaction; it happens only on charging, when \( \ce{PbSO4} \) is converted back to Pb.

• Option (4) PbSO₄(s) + 2H₂O(l) → PbO₂(s) + Pb(s) + 2H₂SO₄ + SO₄²⁻(aq) + H⁺(aq) + 2e⁻ — Incorrect. This is not a discharge reaction; it is a jumbled form of the charging change (\( \ce{PbSO4} \) back to \( \ce{PbO2} \) and Pb) and is not balanced.

NCERT (2026-27 edition):
Secondary Batteries – “… The most important secondary cell is the lead storage battery (Fig. 2.10) commonly used in automobiles and invertors. It consists of a lead anode and a grid of lead packed with lead dioxide (PbO₂) as cathode. A 38% solution of sulphuric acid is used as an electrolyte.
The cell reactions when the battery is in use are given below:
Anode: Pb(s) + SO₄²⁻(aq) → PbSO₄(s) + 2e⁻
Cathode: PbO₂(s) + SO₄²⁻(aq) + 4H⁺(aq) + 2e⁻ → PbSO₄(s) + 2H₂O(l)
i.e., overall cell reaction consisting of cathode and anode reactions is:
Pb(s) + PbO₂(s) + 2H₂SO₄(aq) → 2PbSO₄(s) + 2H₂O(l)
On charging the battery the reaction is reversed and PbSO₄(s) on anode and cathode is converted into Pb and PbO₂, respectively.”