JEE Main 2025 Jan 24 Shift 1, Chemistry Q12: Introduction to Metallurgical Processes

JEE Main2025Jan 24, Shift 1Chemistry

Preparation of potassium permanganate from MnO $_{2}$ involves two step process in which the 1 $^{s t}$ step is a reaction with KOH and KNO $_{3}$ to produce

A
$K_{4} [Mn (OH)_{6}]$
B
$K_{3} Mn O_{4}$
C
$KMn O_{4}$
D
$K_{2} Mn O_{4}$

Solution

The industrial preparation of KMnO $_{4}$ from pyrolusite has two stages.

Stage 1 (alkaline oxidative fusion): MnO $_{2}$ is fused with KOH in the presence of an oxidising agent such as KNO $_{3}$ (or air, or KClO $_{3}$ ). Mn(IV) is oxidised to Mn(VI), giving the green manganate ion:

$Mn O_{2} KOH, KN O_{3}, Δ K_{2} Mn O_{4}$

Stage 2: $K_{2} Mn O_{4}$ is then oxidised (electrolytically or with Cl $_{2}$ /O $_{3}$ ) to the purple Mn(VII) species KMnO $_{4}$ .

The first-step product is therefore $K_{2} Mn O_{4}$ . $∴$ Option (4).

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JEE Main 2025 Jan 24 Shift 1, Chemistry Q12: Introduction to Metallurgical Processes

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