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Fusing MnO2 with KOH (in presence of air or an oxidiser) yields a coloured compound. Identify the product and its colour.

1. K2MnO4, green
2. KMnO4, purple
3. Mn2O3, brown
4. Mn3O4, black

Correct answer: K2MnO4, green

Solution

Alkaline oxidative fusion of MnO2 gives potassium manganate K2MnO4, which is green (Mn in +6).

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