MHT CET · Chemistry · Electrochemistry
Which of the following reactions occurs at cathode during discharging of lead accumulator?
- A \(\mathrm{PbSO}_{4(\mathrm{~s})}+2 \mathrm{e}^{-} \longrightarrow \mathrm{Pb}_{(\mathrm{s})}+\mathrm{SO}_{4 \text { (aq.) }}^{2-}\)
- B \(\mathrm{Pb}_{(\mathrm{s})}+\mathrm{SO}_{4(\text { (aq. })}^{2-} \longrightarrow \mathrm{PbSO}_{4(\mathrm{~s})}+2 \mathrm{e}^{-}\)
- C \(\mathrm{PbO}_{2(\mathrm{~s})}+4 \mathrm{H}_{(\mathrm{aq})}^{+}+\mathrm{SO}_{4(\mathrm{aq})}^{2-}+2 \mathrm{e}^{-}\) \(\longrightarrow \mathrm{PbSO}_{4(s)}+2 \mathrm{H}_2 \mathrm{O}_{(1)}\)
- D \(\mathrm{PbSO}_{4(\mathrm{~s})}+2 \mathrm{H}_2 \mathrm{O}_{(1)} \longrightarrow \mathrm{PbO}_{2(\mathrm{~s})}~+\) \(4 \mathrm{H}_{(\mathrm{aq} .)}^{+}+\mathrm{SO}_{4(\mathrm{aq} .)}^{2-}+2 \mathrm{e}^{-}\)
Answer & Solution
Correct Answer
(C) \(\mathrm{PbO}_{2(\mathrm{~s})}+4 \mathrm{H}_{(\mathrm{aq})}^{+}+\mathrm{SO}_{4(\mathrm{aq})}^{2-}+2 \mathrm{e}^{-}\) \(\longrightarrow \mathrm{PbSO}_{4(s)}+2 \mathrm{H}_2 \mathrm{O}_{(1)}\)
Step-by-step Solution
Detailed explanation
During the discharge of a lead-acid battery, the cathode reaction involves lead dioxide \(\left(\mathrm{PbO}_2\right)\) reacting with sulfuric acid to form lead sulfate \(\left(\mathrm{PbSO}_4\right)\) and water, while releasing electrons.
The correct reaction at the cathode is:
\(\mathrm{PbO}_2+4 \mathrm{H}^{+}+\mathrm{SO}_4^{2-}+2 e^{-} \rightarrow \mathrm{PbSO}_4+2 \mathrm{H}_2 \mathrm{O}\)
Thus, the correct answer is (3).
The correct reaction at the cathode is:
\(\mathrm{PbO}_2+4 \mathrm{H}^{+}+\mathrm{SO}_4^{2-}+2 e^{-} \rightarrow \mathrm{PbSO}_4+2 \mathrm{H}_2 \mathrm{O}\)
Thus, the correct answer is (3).
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