Ncert Exercises & Solutions

When an oxide of manganese (A) is fused with KOH in the presence of an oxidising agent and dissolved in water, it gives a dark green solution of compound (8). Compound (8) disproportionates in neutral or acidic solution to give purple compound (C). An alkaline solirtion of compound (C) oxidises potassium iodide solution to a compound (D) and compound (A) is also formed. Identify compounds A to D and also explain the reactions involved.
Thinking Process

This problem based on the concept of preparation and properties of potassium permanganate.

NEETprep Answer: |tis the method of preparation of potassium permanganate (purple).

T h u s, (A) = M n O_{2} (B) = K_{2} M n O_{4}

(C) = K M N O_{4} (D) = K I O_{3}

2 M n O_{2} + 4 K O H + O_{2} \to 2 K_{2} M n O_{4} + 2 H_{2} O

[A] [B]

3 M n O_{4}^{2 -} + 4 H^{+} \to 2 M n O_{4}^{-} + M n O_{2} + 2 H_{2} O

[C]

2 M n O_{4}^{-} + H_{2} O + K I \to 2 M n O_{2} + 2 O H^{-} + K I O_{3}

[A] [D]

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