JEE Main · 2022 · 26 Jul 2022 · Shift 1 · d and f Block Elements

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The dark purple colour of KMnO₄ disappears in the titration with oxalic acid in acidic medium.
The overall change in the oxidation number of manganese in the reaction is:

(A)5✓ Correct
(B)1
(C)7
(D)2

Answer: (A)

Solution

In acidic medium, permanganate ion (MnO₄⁻) is reduced to Mn²⁺:

MnO_{4}^{-} \to Mn^{2 +}

Oxidation state of Mn changes from +7 (in MnO₄⁻) to +2 (in Mn²⁺).

Change in oxidation number = 7 - 2 = 5.

Answer: (A) 5.

JEE Main · 2022 · 26 Jul 2022 · Shift 1 · Single correct option

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