Write the anode and cathode reactions and the overall cell reaction occurring in a lead storage battery during its use.
Write the anode and cathode reactions and the overall cell reaction occurring in a lead storage battery during its use.
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Solution and Explanation
1. Anode Reaction:
The anode of a lead storage battery is composed of lead (Pb) plates. During discharge, the lead at the anode reacts with the sulfate ions \( \text{SO}_4^{2-} \) to form lead(II) sulfate (PbSO₄). The anode reaction is: \[ \text{Pb (s)} + \text{SO}_4^{2-} \rightarrow \text{PbSO}_4 \, (s) + 2e^- \] This reaction occurs at the **anode**, where oxidation takes place, and lead is converted to lead(II) sulfate while releasing electrons.
2. Cathode Reaction:
The cathode is composed of lead dioxide (PbO₂). During discharge, the lead dioxide reacts with the hydrogen ions \( \text{H}^+ \) and the electrons from the anode to form lead(II) sulfate (PbSO₄) and water. The cathode reaction is: \[ \text{PbO}_2 \, (s) + 4\text{H}^+ \, (aq) + 2e^- \rightarrow \text{PbSO}_4 \, (s) + 2\text{H}_2\text{O} \, (l) \] This reaction occurs at the **cathode**, where reduction takes place, and lead dioxide is reduced to lead(II) sulfate while hydrogen ions are consumed.
3. Overall Cell Reaction:
The overall cell reaction during discharge is the combination of the anode and cathode reactions. The total reaction is: \[ \text{Pb (s)} + \text{PbO}_2 \, (s) + 2\text{H}_2\text{SO}_4 \, (aq) \rightarrow 2\text{PbSO}_4 \, (s) + 2\text{H}_2\text{O} \, (l) \] In this reaction, lead (Pb) and lead dioxide (PbO₂) react with sulfuric acid (\( \text{H}_2\text{SO}_4 \)) to form lead(II) sulfate (PbSO₄) and water during discharge. The overall reaction is a redox reaction where lead and lead dioxide are both converted into lead sulfate.
Conclusion:
- The **anode reaction** involves the oxidation of lead to lead sulfate. - The **cathode reaction** involves the reduction of lead dioxide to lead sulfate and water. - The **overall cell reaction** during discharge is the combination of the two reactions, resulting in the formation of lead sulfate and water.
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