Question

During charging of lead storage battery, the reaction occurring at the cathode is

• A. $ Pb^{2+} +2e^- \to Pb $
  
• B. $ Pb \to Pb^{2+} + 2e^- $
• C. $ PbSO_{4} + 2H_2O \to 2PbO_2 +4H^+ +SO_{4}^{2-} + 2e^- $
• D. $ Pb^{2+} + SO_{4}^{2-} \to Pb SO_4 $

Answer 1

Answer: (A)

(i) Cell reaction during discharge at anode:-
$\rightarrow$ Oxidation reaction at anode[negative electrode]:-
$ \begin{array}{l}
Pb _{( s )} \rightarrow Pb _{( aq )}^{2+}+2 e ^{-}+[\text {oxidation reaction]. } \\
Pb _{( aq )}^{2+}+ SO _{4( aq )}^{2-} \rightarrow PbSO _{4( s )} .
\end{array}
$
Final Reaction:- $Pb _{( s )}+ SO _{4( aq )}^{2-} \rightarrow PbSO _{4( s )}+2 e ^{-}$[overall oxidation at anode].
(ii) Cell reaction during recharge:-
The reverse of oxidation at anode during discharge is the reduction reaction at cathode during recharging.
$
\begin{array}{l}
Pb _{( aq )}^{2+}+2 e ^{-} \rightarrow Pb _{( s )}-{ }^{-} \\
PbSO _{4( s )} \rightarrow Pb _{( aq )}^{2+}+ SO _{4( aq )}^{2-}
\end{array}
$
Final Reaction:- $PbSO _{4( s )}+2 e ^{-} \rightarrow Pb _{( s )}+ SO _{4( aq )}^{2-}$