Which of the following reactions occur at the cathode during the charging of a lead storage battery?

Options

A. `Pb^(2+)+2e^(-)rarrPb`
B. `Pb^(2+)+SO_(4)""^(2-)rarrPbSO_(4)`
C. `Pb rarr Pb^(2+)+2e^(-)`
D. `PbSO_(4)+2H_(2)Orarr PbO_(2)+2H^(+)+SO_(2)""^(2-)+2e^(-)`

Answer

To determine which reactions occur at the cathode during the charging of a lead storage battery, we need to understand the processes involved in both charging and discharging of the battery.

### Step-by-Step Solution:

1. **Understand the Components of the Lead Storage Battery**:
- The lead storage battery consists of lead (Pb), lead dioxide (PbO2), and lead sulfate (PbSO4) as its main components. The electrolyte is typically sulfuric acid (H2SO4).

2. **Identify the Reactions During Discharge**:
- During the discharge of a lead storage battery, the following reactions occur:
- At the anode (oxidation):
\[ \text{Pb} + \text{SO}_4^{2-} \rightarrow \text{PbSO}_4 + 2e^- \]
- At the cathode (reduction):
\[ \text{PbO}_2 + 4\text{H}^+ + \text{SO}_4^{2-} + 2e^- \rightarrow \text{PbSO}_4 + 2\text{H}_2\text{O} \]

3. **Understand the Charging Process**:
- During charging, the reactions are reversed. The lead sulfate formed during discharge is converted back to lead and lead dioxide.

4. **Identify the Reaction at the Cathode During Charging**:
- The reverse reaction at the cathode during charging is:
\[ \text{PbSO}_4 + 2\text{H}_2\text{O} + 2e^- \rightarrow \text{PbO}_2 + 4\text{H}^+ + \text{SO}_4^{2-} \]
- This indicates that lead sulfate (PbSO4) and water (H2O) are converted back into lead dioxide (PbO2) and sulfate ions (SO4^2-).

5. **Conclusion**:
- Therefore, the reaction that occurs at the cathode during the charging of a lead storage battery is:
\[ \text{PbSO}_4 + 2\text{H}_2\text{O} + 2e^- \rightarrow \text{PbO}_2 + 4\text{H}^+ + \text{SO}_4^{2-} \]