How is `KMnO_(4)` [Potassium permanganate] is prepared from `MnO_(2)`? Write equations.

Explanation

Step 1 : The finely powdered `MnO_2` (pyrolusite)is fused with KOH (potassium hydroxide)in the presence of excess air and an oxidizing agent like `KNO_3`, to get green coloured potassium magnanate.
`2MnO_2 + 4KOH + O_2 to 2 K_2 MnO_4 + 2H_2 O`
Step 2 : Potassium maganate in acidic or neutral medium undergoes disproportionate to give permaganate `3MnO_(4)^(2-) + 4H^(+) to 2MnO_(4)^(-) + MnO_2 + H_2 O` .