JEE Main · 2022 · 26 Jun 2022 · Shift 2 · Redox Reactions and Electrochemistry

Which one of the following is an example of disproportionation reaction?

(A) $3 MnO X_{4} X^{2 -} + 4 H X^{+} \to 2 MnO X_{4} X^{-} + MnO X_{2} + 2 H X_{2} O$ ✓ Correct
(B) $MnO X_{4} X^{2 -} + 4 H X^{+} + 4 e X^{-} \to MnO X_{2} + 2 H X_{2} O$
(C) $10 I X^{-} + 2 MnO X_{4} X^{-} + 16 H X^{+} \to 2 Mn X^{2 +} + 8 H X_{2} O + 5 I X_{2}$
(D) $8 MnO X_{4} X^{-} + 3 S X_{2} O X_{3} X^{2 -} + H X_{2} O \to 8 MnO X_{2} + 6 SO X_{4} X^{2 -} + 2 OH X^{-}$

Answer: (A)

Solution

A disproportionation reaction is one in which the same element undergoes both oxidation and reduction simultaneously.

In option (A):

3 MnO X_{4} X^{2 -} + 4 H X^{+} \to 2 MnO X_{4} X^{-} + MnO X_{2} + 2 H X_{2} O

Manganese in

MnO X_{4} X^{2 -}

(oxidation state +6) is:

This is a classic disproportionation reaction where the same species undergoes both oxidation and reduction.

JEE Main · 2022 · 26 Jun 2022 · Shift 2 · Single correct option