Question

What happens when KMnO₄ is warmed gently with conc. H₂SO₄?

Answer 1

Cold and concentrated H₂SO₄ treatment produces manganese heptoxide (Mn₂O₇), which can break down into manganese dioxide and oxygen.

\[\ce{2KMnO4 + H2SO4 ->[Cold] Mn2O7 + K2SO4 + H2O}\]

\[\ce{2Mn2O7 -> 4MnO2 + 3O2}\]

When warmed gently with conc. H₂SO₄, it gives oxygen.

\[\ce{4KMnO4 + 6H2SO4 ->[Warm] 2K2SO4 + 4MnSO4 + 6H2O + 5O2}\]