Question

What is the action of KMnO₄ in an acidic medium on the following?

SO₂

Write a balanced equation.

Answer 1

It oxidises sulphur dioxide to sulphuric acid.

\[\ce{2KMnO4 + 3H2SO4 -> K2SO4 + 2MMnSO4 + 3H2O + 5O}\]

\[\ce{[SO2 + H2O + O -> H2SO4] \times 5}\]

\[\ce{\overline{2\text{KMnO}_4 + 5\text{SO}_2 + 2\text{H}_2\text{O} \leftarrow \text{K}_2\text{SO}_4 + 2\text{MnSO}_4 + 2\text{H}_2\text{SO}_4}}\]

or,

\[\ce{MnO^-_4 + 5SO2 + 2H2O -> 5SO^{2-}_4 + 2Mn^{2+} + 4H+}\]