JEE Main 2025 — Electrochemistry Question with Solution

(A) An aqueous solution of AgNO${}_3$ using silver electrodes.

Cathode - Reduction - $$A{g}_{(aq)}^{+}+e^{-}\to Ag(s)$$

Anode - Oxidation - $$Ag(s)\to A{g}_{(aq)}^{+}+e^{-}$$

Solid silver will be deposited at the cathode. Solid anode (silver) will dissolve, releasing silver ions into the solution.

So, there is no formation of O${}_2$ gas in this electrolysis.

(B) An aqueous solution of AgNO${}_3$ using platinum electrodes.

Cathode - Reduction - $$A{g}_{(aq)}^{+}+e^{-}\to Ag(s)$$

Anode - Oxidation - $$2H_{2}O\to 4H^{+}+O_2+4e^{-}$$

When platinum electrodes are used, Ag${}^{+}$ from solution is reduced and deposited at cathode whereas O${}_2$ is produced at the anode.

(C) A dilute soution of H${}_2$SO${}_4$ using platinum electrodes.

Cathode - Reduction - $$2H^{+}+2e^{-}\to H_2$$

Anode - Oxidation - $$2H_{2}O\to O_2+4H^{+}+4e^{-}$$

H${}_2$ gas is produded at the cathode and O${}_2$ gas is produced at the anode.

(D) a high concentration solution of H${}_2$SO${}_4$ using platinum electrodes.

O${}_2$ gas is not formed in this case.

Cathode - Reduction - The substance formed is H${}_2$ gas.

Anode - Oxidation - The substance formed is not O${}_2$ gas.

So, statements (B) and (C) are correct.