Pyrolusite is MnO2 used to prepare KMnO4. Steps are : Mn O_{2} \rightarrow_{}^{I} Mn O_{4}^{2 -} \rightarrow_{}^{II} MnO_{4}^{-} Steps I and II are respectively :

Engineering

Chemistry

Dichromate and Permanganate Ion Reactions

Question

Pyrolusite is MnO₂ used to prepare KMnO₄. Steps are :

$Mn O_{2} \to_{}^{I} Mn O_{4}^{2 -} \to_{}^{II} {MnO}_{4}^{-}$

Steps I and II are respectively :

Fuse with concentrated HNO₃ / air, electrolytic reduction

Fuse with KOH / air, electrolytic oxidation

Fuse with KOH / KNO₂, electrolytic oxidation

Dissolve in H₂O, oxidation

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Fuse with KOH in presence of air or oxidising agents like KNO₂ , KClO₃ etc.

2MnO₂ + 4KOH + O₂ → 2K₂MnO₄ + 2H₂O

MnO₄^2– $\overset{electrolytic oxidation}{\to}$ MnO₄^– + e^–