Explain working of lead storage battery.
The reaction occurring in lead storage battery is a kind of comproportionation. The other name of comproportionation is symproportionation. It is a chemical reaction in which two reactants, containing the same element in different oxidation state, will form a product in which the elements reach the same oxidation state. Reaction occurring in lead storage battery is as shown.
$$P b(s)+P b O_{2}(s)+2 H_{2} S O_{4}(a q) \rightarrow 2 P b S O_{4}(s)+2 H_{2} O(l)$$
This consists of gas at 1 atmospheric pressure bubbling over a platinum electrode immersed in $$1 \mathrm{M}$$ HCl at $$25^{\circ} \mathrm{C}(298 \mathrm{K})$$ as shown in the figure. The platinum electrode is coated with platinum black to increase its surface. The hydrogen electrode thus constructed forms a half cell which on coupling with any other half cell begins to work on the principle of oxidation or reduction. Electrode depending upon the circumstances work both an anode or cathode. Cell reaction of standard hydrogen electrode (SHE) when it acts as anode is:
$$H_{2(g)} \rightarrow 2 H^{+}+2 e^{-}$$
It is as represented as
$$H_{2(g)}(1 a t m) P t \mid H_{3} O_{(a q)}^{+}(1.0 M)$$
When it acts as a cathode, the cell reaction is
$$2 H^{+}+2 e^{-} \rightarrow H_{2(aq)}$$
and it is represented as
$$H_{3} O_{(a q)}^{+}(1.0 M) \mid(1 a t m) P t$$
