1.

How is potassium permanganate ( KMnO_4) prepared from MnO_2 ? write the equation.

Answer»

Solution :By fusion of `MnO_2` with an alkali metal hydroxide and an oxidising agent `KNO_3` gives `K_2MnO_4`, which on acidification gives permanganate.
`2MnO_2 + 4KOH + O_2 to 2K_2MnO_4 + 2H_2O`
`3MnO_(4)^(2-) + 4H^(+) to 2MnO_(4)^(-) + MnO_(2) + 2H_2O`
OR
`MnO_2 underset("Oxidised with air")overset("Fused with KOH")(rarr)MnO_(4)^(2-)`
`MnO_(4)^(2-) underset("In alkaline solution")overset("Electrolytic oxidation")(rarr)MnO_(4)^(-)`


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