Write cell reactions in lead storage battery during discharge.

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Solution

Oxidation reaction at anode:
$P b_{(s)} \to P b_{(a q)}^{2 +} + 2 e^{-}$ (oxidation)
$P b_{(a q)}^{2 +} + S O_{4_{(a q)}}^{2 -} \to P b S O_{4 (s)}$ (precipitation)
$P b_{(s)} + S O_{4_{(a q)}}^{2 -} \to P b S O_{4 (s)} + 2 e^{-}$ (Overall reaction at anode during discharge)
Reduction reaction at cathode:
$P b O_{2 (s)} + 4 H_{(a q)}^{+} + 2 e^{-} \to P b_{(a q)}^{2 +} + 2 H_{2} O$ (reduction)
$P b_{(a q)}^{2 +} + S O_{4 (a q)}^{2 -} \to P b S O_{4 (s)}$ (precipitation)
$P b O_{2 (s)} + 4 H_{(a q)}^{+} + S O_{4_{(a q)}}^{2 -} + 2 e^{-} \to P b S O_{4 (s)} + 2 H_{2} O_{(l)}$ (Overall reaction at cathode during discharge)
The overall cell reaction during discharging is:
$P b_{(s)} + S O_{4_{(a q)}}^{2 -} \to P b S O_{4 (s)} + 2 e^{-}$
$P b O_{2 (s)} + H_{(a q)}^{+} + S O_{4_{(a q)}}^{2 -} + 2 e^{-} \to P b S O_{4 (s)} + 2 H_{2} O_{(l)}$
$P b_{(s)} + P b O_{2 (g)} + 2 H_{2} S O_{4 (a q)} \to 2 P b S O_{4 (s)} + 2 H_{2} O_{(l)}$

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