Question

A blackish brown solid A when fused with sodium or potassium hydroxide in
the presence of air, produces a dark green-coloured mass of compound B,
which on electrolytic oxidation gives a dark purple-coloured compound C.
Identify A, B and C. What happens when acidic solution of green-coloured
compound B is allowed to stand for some time? Write the reactions involved.

Answer 1

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Answer 2

Hello Dear,

◆ Identification -

Compound A => MnO2

Compound B => K2MnO4

Compound C => KMnO4

● Reactions involved -

(1) MnO2 (A) is fused with KOH in presence of air to form K2MnO4 (B).

2MnO2 + 4KOH + O2 --> 2K2MnO4 + 2H2O

(2) K2MnO4 (B) on electrolytic oxidation gives KMnO4 (C).

2K2MnO4 + H2O + O- --> 2KMnO4 + 2KOH

(3) K2MnO4 (B) when allowed to stand for some time, it gets oxidized to KMnO4 (C) by reaction with CO2 in air.

3K2MnO4 + 2CO2 --> 2K2CO3 + 2MnO2 + 2KMnO4

Hope this helps you. Thanks for asking..