Q3 / 75 · JEE Main 2025 (29 Jan Shift 2) · Chemistry
$\mathrm{O}_2$ gas will be evolved as a product of electrolysis of :
(A) an aqueous solution of $\mathrm{AgNO}_3$ using silver electrodes.
(B) an aqueous solution of $\mathrm{AgNO}_3$ using platinum electrodes.
(C) a dilute solution of $\mathrm{H}_2 \mathrm{SO}_4$ using platinum electrodes.
(D) a high concentration solution of $\mathrm{H}_2 \mathrm{SO}_4$ using platinum electrodes.
Choose the correct answer from the options given below :
- A(A) and (C) only
- Correct answerB(B) and (C) only
- C(A) and (D) only
- D(B) and (D) only
Solution
When an aqueous solution of $\mathrm{AgNO}_3$ is electrolysed using Pt electrodes
Cathode: $\mathrm{Ag}^{+}(\mathrm{aq})+\mathrm{e}^{-} \rightarrow \mathrm{Ag}(\mathrm{s})$
Anode : $2 \mathrm{H}_2 \mathrm{O}(\mathrm{l}) \rightleftharpoons 4 \mathrm{H}^{+}(\mathrm{aq})+\mathrm{O}_2(\mathrm{~g})+4 \mathrm{e}^{-}$
$\Rightarrow$ When dilute $\mathrm{H}_2 \mathrm{SO}_4$ is electrolysed using Pt electrodes
$\Rightarrow$ When dilute $\mathrm{H}_2 \mathrm{SO}_4$ is electrolysed using Pt electrodes
Anode : $2 \mathrm{H}_2 \mathrm{O}(\mathrm{l}) \rightarrow \mathrm{O}_2(\mathrm{~g})+4 \mathrm{H}^{+}(\mathrm{aq})+4 \mathrm{e}^{-}$
Cathode: $2 \mathrm{H}^{+}(\mathrm{aq})+2 \mathrm{e}^{-} \rightarrow \mathrm{H}_2(\mathrm{~g})$
Hence, the correct answer is option: 'B'.