KCET · Chemistry · Electrochemistry
In \( \mathrm{H}_{2}-\mathrm{O}_{2} \) fuel cell the reaction occurring at cathode is
- A \( \left.2 \mathrm{H}_{2}\right)(g)+\mathrm{O}_{2}(g) \rightarrow 2 \mathrm{H}_{2} \mathrm{O}(l) \)
- B \( \mathrm{O}_{2}(g)+2 \mathrm{H}_{2} \mathrm{O}(l)+4 e^{-} \rightarrow 4 \mathrm{OH}^{-}(a q) \)
- C \( H^{+}+e^{-} \rightarrow \frac{1}{2} H_{2} \)
- D \( \mathrm{H}^{+}(a q)+\mathrm{OH}^{-}(a q) \rightarrow \mathrm{H}_{2} \mathrm{O}(l) \)
Answer & Solution
Correct Answer
(B) \( \mathrm{O}_{2}(g)+2 \mathrm{H}_{2} \mathrm{O}(l)+4 e^{-} \rightarrow 4 \mathrm{OH}^{-}(a q) \)
Step-by-step Solution
Detailed explanation
The reaction occurring in \( \mathrm{H}_{2}-\mathrm{O}_{2} \) fuel cells are:
\[
\begin{array}{ll}
\text { At anode : } & 2 \mathrm{H}_{2}(g)+4 \mathrm{OH}^{-}(a q) \rightarrow 4 \mathrm{H}_{2} \mathrm{O}(l)+4 e^{-} \\
\text {At cathode : } & \mathrm{O}_{2}(g)+2 \mathrm{H}_{2} \mathrm{O}(l)+4 e^{-} \rightarrow 4 \mathrm{OH}^{-}(a q)
\end{array}
\]
\[
\text { Net reaction : } 2 \mathrm{H}_{2}(g)+\mathrm{O}_{2}(g) \rightarrow 2 \mathrm{H}_{2} \mathrm{O}(l)
\]
\[
\begin{array}{ll}
\text { At anode : } & 2 \mathrm{H}_{2}(g)+4 \mathrm{OH}^{-}(a q) \rightarrow 4 \mathrm{H}_{2} \mathrm{O}(l)+4 e^{-} \\
\text {At cathode : } & \mathrm{O}_{2}(g)+2 \mathrm{H}_{2} \mathrm{O}(l)+4 e^{-} \rightarrow 4 \mathrm{OH}^{-}(a q)
\end{array}
\]
\[
\text { Net reaction : } 2 \mathrm{H}_{2}(g)+\mathrm{O}_{2}(g) \rightarrow 2 \mathrm{H}_{2} \mathrm{O}(l)
\]
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