Preparation of potassium permanganate from MnO₂ involves two step process in which the 1st step is a reaction with KOH and KNO₃ to produce

Solution

Chemistry ma’am · 4 steps

In the fusion step, KNO₃ can only push manganese from +4 up to +6, which gives green manganate.

1. Alkaline fusion. MnO₂ is fused with KOH, and KNO₃ acts as the oxidising agent. Manganese goes from +4 to +6 while nitrogen goes from +5 to +3, so each side moves by 2 electrons.

   MnO₂ + 2KOH + KNO₃ → K₂MnO₄ + KNO₂ + H₂O

2. Identify the product. In K₂MnO₄, 2 + x - 8 = 0 gives x = +6. This is potassium manganate, a green solid that stays stable only in strongly alkaline conditions.
3. Second step. The manganate is then oxidised to permanganate, either electrolytically or by disproportionation in neutral or acidic solution: 3MnO₄²⁻ + 4H⁺ → 2MnO₄⁻ + MnO₂ + 2H₂O. Only now does Mn reach +7.
4. So. The first step produces K₂MnO₄, option (c).

The idea to keep. Remember the sequence MnO₂ (+4) to green K₂MnO₄ (+6) by alkaline fusion, then to purple KMnO₄ (+7) by electrolytic oxidation or disproportionation.

Answer from the NTA final answer key. Solution by PrepWiser.