Which of the following electrolyte can be sued to obtain \(\mathrm{H}_{2} \mathrm{~S}_{2} \mathrm{O}_{8}\) by the process of electrolysis?

(C) Concentrated solution of sulphuric acid

(A) Dilute solution of sodium sulphate

(B) Dilute solution of sulphuric acid

(D) Acidified dilute solution of sodium sulphate.

JEE Main · 2025 · 22 Jan 2025 · Shift 1 · Redox Reactions and Electrochemistry

Which of the following electrolyte can be sued to obtain

H_{2} S_{2} O_{8}

by the process of electrolysis?

Answer: (C)

Peroxodisulphuric acid is made by anodic oxidation of the bisulphate ion:

2 H S O_{4}^{-} \to H_{2} S_{2} O_{8} + 2 e^{-}

This oxidation requires a high concentration of

H S O_{4}^{-}

at the anode, which only concentrated sulphuric acid provides. In dilute sulphuric acid or dilute/acidified sodium sulphate,

H S O_{4}^{-}

concentration is too low and water oxidation to

O_{2}

dominates instead. Concentrated sulphuric acid is the electrolyte that yields peroxodisulphuric acid.

JEE Main · 2025 · 22 Jan 2025 · Shift 1 · Single correct option