Question:
Which of the following changes takes place at positive electrode during recharging of lead accumulator?
Which of the following changes takes place at positive electrode during recharging of lead accumulator?
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Recharging a battery is literally running the discharge reactions perfectly backwards! Just remember: Discharge turns everything into $\text{PbSO}_4$. Recharge turns it all back into $\text{Pb}$ and $\text{PbO}_2$. Oxidation always happens at the Anode!
Updated On: Aug 19, 2026
- Pb is oxidised to $\text{PbSO}_{4}$
- $\text{PbSO}_{4}$ is oxidised to $\text{PbO}_{2}$
- $\text{PbSO}_{4}$ is reduced to Pb
- $\text{PbO}_{2}$ is reduced to $\text{PbSO}_{4}$
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The Correct Option is B
Solution and Explanation
Step 1: Understanding the Question:
The question asks for the specific chemical reaction occurring at the positive terminal of a Lead Storage Battery (accumulator) during the recharging phase (when it acts as an electrolytic cell).
Step 2: Detailed Explanation:
Let's break down the life cycle of a lead accumulator:
1. During Discharging (Acting as a Galvanic Cell):
- The battery produces power.
- Negative electrode (Anode): Spongy Lead ($\text{Pb}$) is oxidized into solid $\text{PbSO}_4$.
- Positive electrode (Cathode): Lead dioxide ($\text{PbO}_2$) is reduced into solid $\text{PbSO}_4$.
- Notice that both electrodes end up heavily coated in the same white solid, $\text{PbSO}_4$.
2. During Recharging (Acting as an Electrolytic Cell):
- External electrical power is pumped back into the battery to force the reactions to run in reverse.
- The terminals stay physically the same, but their roles swap. The positive electrode now acts as the Anode (where forced oxidation occurs), and the negative electrode acts as the Cathode (where forced reduction occurs).
- At the Positive Electrode (+): The solid $\text{PbSO}_4$ coating is stripped of electrons and forced to oxidize back into brown Lead dioxide ($\text{PbO}_2$).
- At the Negative Electrode (-): The solid $\text{PbSO}_4$ coating gains electrons and is forced to reduce back into spongy Lead ($\text{Pb}$).
Therefore, at the positive electrode during recharging, $\text{PbSO}_4$ is oxidized to $\text{PbO}_2$.
Step 3: Final Answer:
The change is $\text{PbSO}_{4}$ is oxidised to $\text{PbO}_{2}$, matching option (b).
The question asks for the specific chemical reaction occurring at the positive terminal of a Lead Storage Battery (accumulator) during the recharging phase (when it acts as an electrolytic cell).
Step 2: Detailed Explanation:
Let's break down the life cycle of a lead accumulator:
1. During Discharging (Acting as a Galvanic Cell):
- The battery produces power.
- Negative electrode (Anode): Spongy Lead ($\text{Pb}$) is oxidized into solid $\text{PbSO}_4$.
- Positive electrode (Cathode): Lead dioxide ($\text{PbO}_2$) is reduced into solid $\text{PbSO}_4$.
- Notice that both electrodes end up heavily coated in the same white solid, $\text{PbSO}_4$.
2. During Recharging (Acting as an Electrolytic Cell):
- External electrical power is pumped back into the battery to force the reactions to run in reverse.
- The terminals stay physically the same, but their roles swap. The positive electrode now acts as the Anode (where forced oxidation occurs), and the negative electrode acts as the Cathode (where forced reduction occurs).
- At the Positive Electrode (+): The solid $\text{PbSO}_4$ coating is stripped of electrons and forced to oxidize back into brown Lead dioxide ($\text{PbO}_2$).
- At the Negative Electrode (-): The solid $\text{PbSO}_4$ coating gains electrons and is forced to reduce back into spongy Lead ($\text{Pb}$).
Therefore, at the positive electrode during recharging, $\text{PbSO}_4$ is oxidized to $\text{PbO}_2$.
Step 3: Final Answer:
The change is $\text{PbSO}_{4}$ is oxidised to $\text{PbO}_{2}$, matching option (b).
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