Question

During the charging of lead storage battery, the reaction at anode is represented by:
A. $P{b^{2 + }} + SO_4^{2 - } \to PbS{O_4}$
B. $PbS{O_4} + 2{H_2}O \to Pb{O_2} + SO_4^{2 - } + 4{H^ + } + 2e$
C. $Pb \to P{b^{2 + }} + 2e$
D. $P{b^{2 + }} + 2e \to Pb$

Answer 1

Hint: In the anode of lead storage battery oxidation reaction takes place where lead electrons are removed and added to cathode. The oxidation reaction is defined as loss of electrons.

Complete answer:
Given,
The lead storage battery is also known as lead acid battery. The lead storage battery can store a high amount of charge in it and can give huge amounts of current for a short span of time. The lead storage battery is the oldest type of battery which can be recharged and re-use. They are also used as an energy storing device.
In a lead storage battery, the positive plate and the negative plate are formed of two spirals of lead foil which are separated from each other by the sheet of cloth.
When the lead storage battery is discharged, it can be recharged again and the chemistry in both the states is different.
Discharged state:
Both the positive plate and the negative plate in the discharged state form the lead sulfate. The electrolyte present loses its dissolved sulfuric acid. In the discharged process, the electrons from the negative plate move to the cell at the positive plate present in the external circuit.
The reaction is shown below.
Negative plate reaction: $Pb(s) + HSO_4^ - (aq) \to PbS{O_4}(s) + {H^ + }(aq) + 2e$
Positive plate reaction: $Pb{O_2}(s) + HSO_4^ - (aq) + 3{H^ + }(aq) + 2e \to PbS{O_4}(s) + 2{H_2}O(l)$
Overall reaction: $Pb(s) + Pb{O_2}(s) + 2{H^ + }(aq) + HSO_4^ - (aq) \to 2PbS{O_4}(s) + 2{H_2}O(l)$
Charged state:
In the charged state, the cell consists of the negative plate formed of lead and a positive plate formed of lead oxide dipped in the electrolyte containing 4.2 M sulphuric acid. In charging state, the electrons leave the positive plate and added to negative plate by charging the source.
The reaction is shown below.
Negative plate reaction: $PbS{O_4}(s) + {H^ + }(aq) + 2e \to Pb(s) + HSO_4^ - (aq)$
Positive plate reaction: $PbS{O_4} + 2{H_2}O \to Pb{O_2} + SO_4^{2 - } + 4{H^ + } + 2e$
Overall reaction: $2PbS{O_4}(s) + 2{H_2}O(l) \to Pb(s) + Pb{O_2}(s) + 2{H^ + }(aq) + 2HSO_4^ - (aq)$
Thus, during the charging of lead storage battery, the reaction at anode is represented by:
$PbS{O_4} + 2{H_2}O \to Pb{O_2} + SO_4^{2 - } + 4{H^ + } + 2e$
Therefore, the correct option is B.

Note:
The reaction of the charged state is opposite to the discharged state. Usually anode is treated as negative and cathode as positive but in lead storage batteries the charges are opposite in the electrodes.