Question

In lead storage battery during discharging___ a) pH decreases b) pH remains same c) pH increases d) pH increases or decreases depending upon the extent of discharging​

Answer 1

The density of an electrolyte in a lead storage battery decreases as it is discharged.

Answer 2

In the lead storage battery during discharging pH of the electrolyte increases. Thus, the correct option is (c).

Explanation:

• In the lead storage battery, the oxidation and reduction reactions during discharging can be given as:

        At anode: Oxidation half-cell reaction

        $\[Pb(s) + S{O_4}^{2 - } \to PbS{O_4}(s) + 2{e^ - }\]$

        At cathode: Reduction half-cell reaction

         $\[Pb{O_2} + 4{H^ + }(aq.) + S{O_4}^{2 - }(aq.) + 2{e^ - } \to PbS{O_4}(s) + 2{H_2}O(l)\]$

• At anode, oxidation of lead to lead sulphate takes place while at cathode, reduction of $\[Pb{O_2}\]$ to $\[PbS{O_4}\]$ takes place.
• Sulphuric acid is consumed during discharging in the lead storage battery and water is produced.
• Therefore, the pH of the electrolyte increases.