Question 42

For lead storage battery pick the correct statements
A. During charging of battery, PbSO$$_4$$ on anode is converted into PbO$$_2$$
B. During charging of battery, PbSO$$_4$$ on cathode is converted into PbO$$_2$$
C. Lead storage battery consists of grid of lead packed with PbO$$_2$$ as anode
D. Lead storage battery has ~38% solution of sulphuric acid as an electrolyte
Choose the correct answer from the options given below:

Solution

Detailed Solution

Problem Statement: For a lead storage battery, evaluate the correctness of the statements below and choose the correct option.

A. During charging of battery, PbSO4 on anode is converted into PbO2.

B. During charging of battery, PbSO4 on cathode is converted into PbO2.

C. Lead storage battery consists of a grid of lead packed with PbO2 as anode.

D. Lead storage battery has ~38% solution of sulphuric acid as an electrolyte.

Theoretical Principles & Cell Reactions

A lead storage battery is a secondary cell (rechargeable). To evaluate the statements, we analyze its composition and chemical processes during discharging and charging cycles.

1. Battery Construction (Standard State)

Anode: Spongy Lead (Pb).
Cathode: A grid of lead packed with Lead Dioxide (PbO2).
Electrolyte: An aqueous solution of Sulphuric Acid (H2SO4), approximately 38% by mass (density ≈ 1.30 g/mL).

2. Chemical Reactions During Charging

During the charging process, an external electrical source reverses the spontaneous cell reactions. The PbSO4 deposited during discharge is converted back:

At Anode (Reduction during charging):

PbSO4(s) + 2e− → Pb(s) + SO42−(aq)

At Cathode (Oxidation during charging):

PbSO4(s) + 2H2O(l) → PbO2(s) + SO42−(aq) + 4H+(aq) + 2e−

Statement Evaluation Matrix

Statement	Analysis	Status
A	During charging, PbSO4 on the anode is reduced back to spongy lead (Pb), not PbO2.	Incorrect
B	During charging, PbSO4 on the cathode is oxidized to Lead Dioxide (PbO2).	Correct
C	The grid packed with PbO2 acts as the cathode, while the grid packed with spongy lead serves as the anode.	Incorrect
D	A standard lead storage battery uses a ~38% H2SO4 solution as its electrolyte environment.	Correct

Final Conclusion

Statements B and D are completely precise and scientifically accurate based on core electrochemical principles.

Correct Answer: B, D only

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