Question

Which among the following equations represents the reduction reaction taking place in lead accumulator at positive electrode, while it is being used as a source of electrical energy?

Options

• \[\ce{Pb -> Pb^{2+}}\]

• \[\ce{Pb^{4+} -> Pb}\]

• \[\ce{Pb^{2+} -> Pb}\]

• \[\ce{Pb^{4+} -> Pb^{2+}}\]

Answer 1

\[\ce{Pb^{4+} -> Pb^{2+}}\]

Explanation

The reaction involved for lead accumulator during discharging i.e., when cell is in use are

At anode: \[\ce{Pb(s) + HSO^-_4 (aq) -> PbSO4(s) + H+ + 2e-}\]

At cathode: \[\ce{PbO2(s) + 3H+ (aq) + HSO^-_4 (aq) + 2e^- -> PbSO4(s) + 2H2O(l)}\]

Overall reaction: \[\ce{Pb(s) + PbO2 (s) + 2H+ + 2HSO^-_4 (aq) -> 2PbSO4 (s) + 2H2O(l)}\]