Q45 / 160 · JIPMER 2009 · Chemistry
Which of the following is not correct regarding the elecolytic preparation of $\mathrm{H}_2 \mathrm{O}_2$ ?
- ALead is used as cathode
- B$50 \% \mathrm{H}_2 \mathrm{SO}_4$ is used
- Correct answerCHydrogen is liberated at anode
- DSulphuric acid undergoes oxidation
Solution
$\mathrm{H}_2 \mathrm{O}_2$ can be prepared by electrolysis of $50 \%$ $\mathrm{H}_2 \mathrm{SO}_4$. In this method, hydrogen is liberated at cathode.
$\mathrm{H}_2 \mathrm{SO}_4 \rightleftharpoons 2 \mathrm{H}^{+}+2 \mathrm{HSO}_4^{-}$
$\begin{aligned} & \text { At anode : } 2 \mathrm{HSO}_4^{-} \longrightarrow \mathrm{H}_2 \mathrm{~S}_2 \mathrm{O}_8+2 e^{-} \\ & \mathrm{H}_2 \mathrm{~S}_2 \mathrm{O}_8+2 \mathrm{H}_2 \mathrm{O} \longrightarrow 2 \mathrm{H}_2 \mathrm{SO}_4+\mathrm{H}_2 \mathrm{O}_2 \\ & \text { At cathode }: 2 \mathrm{H}^{+}+2 e^{-} \longrightarrow \mathrm{H}_2 \uparrow\end{aligned}$
Hence, the correct answer is option: 'C'.