Question

What happens when ${\mathrm{SO}}_2$ is passed in ${\mathrm{KMnO}}_4$ acidified solution?

Answer 1

Chemical Reaction

• The chemical reaction between Sulphur dioxide $\left({\mathrm{SO}}_2\right)$ and ${\mathrm{KMnO}}_4$ is shown below.

$5{\mathrm{SO}}_2\left(\mathrm{g}\right)+2{\mathrm{KMnO}}_4\left(\mathrm{s}\right)+2{\mathrm{H}}_2\mathrm{O}\left(\mathrm{l}\right)\to {\mathrm{K}}_2{\mathrm{SO}}_4\left(\mathrm{aq}\right)+2{\mathrm{MnSO}}_4\left(\mathrm{aq}\right)+2{\mathrm{H}}_2{\mathrm{SO}}_4\left(\mathrm{l}\right)$

Explanation

• The above reaction is an example of a redox reaction, where oxidation, as well as reduction, occurs simultaneously.
• Sulfur dioxide is a strong reducing agent so it reduces the potassium permanganate (purple color) to a colorless solution of potassium sulfate.
• Potassium permanganate is a strong oxidizing agent so oxidizes sulfur dioxide to potassium sulfate.