The reaction between potassium permanganate (KMnO4) and sulfur dioxide (SO2) is a redox reaction in an acidic solution. Here's a breakdown:

Reaction Equation:

2KMnO4 + 5SO2 + 2H2O → K2SO4 + 2MnSO4 + 2H2SO4

Explanation:

* Oxidation: SO2 is oxidized to sulfate ions (SO4^2-). The oxidation number of sulfur increases from +4 in SO2 to +6 in SO4^2-.

* Reduction: KMnO4 is reduced to manganese(II) ions (Mn^2+). The oxidation number of manganese decreases from +7 in KMnO4 to +2 in Mn^2+.

Steps:

1. Balancing in acidic solution:

* Half-reaction for oxidation:

SO2 + 2H2O → SO4^2- + 4H+ + 2e-

* Half-reaction for reduction:

MnO4^- + 8H+ + 5e- → Mn^2+ + 4H2O

2. Multiply the oxidation half-reaction by 5 and the reduction half-reaction by 2 to balance electrons:

* 5SO2 + 10H2O → 5SO4^2- + 20H+ + 10e-

* 2MnO4^- + 16H+ + 10e- → 2Mn^2+ + 8H2O

3. Add the two half-reactions together and cancel out common species:

2MnO4^- + 5SO2 + 2H2O → 2Mn^2+ + 5SO4^2- + 4H+

4. Add potassium ions (K+) to balance the charge:

2KMnO4 + 5SO2 + 2H2O → K2SO4 + 2MnSO4 + 2H2SO4

Observations:

* The purple solution of potassium permanganate turns colorless as it is reduced.

* The reaction releases heat, indicating it is exothermic.

Applications:

This reaction is used in analytical chemistry to determine the concentration of sulfur dioxide in air or other samples.