When SO2 is passed through acidified KMnO4, the following reactions occur:

1. Oxidation of SO2:
- The acidified KMnO4 acts as an oxidizing agent in this reaction.
- The MnO4- ions in KMnO4 are reduced to Mn2+ ions.
- SO2 is oxidized to form sulfuric acid (H2SO4).

2. Reduction of KMnO4:
- KMnO4 is reduced to Mn2+ ions in the presence of acid and reducing agents like SO2.
- The Mn2+ ions produced are pale pink in color.

3. Color Change:
- The acidified KMnO4 solution initially has a purple color due to the presence of MnO4- ions.
- As SO2 is passed through the solution, the purple color gradually fades, indicating the reduction of MnO4- ions to Mn2+ ions.

Overall Reaction:
- The overall reaction can be represented as:
5SO2 + 2KMnO4 + 2H2O → 5H2SO4 + 2Mn2+ + K2SO4

Explanation:
- When SO2 is passed through acidified KMnO4, the SO2 acts as a reducing agent while KMnO4 acts as an oxidizing agent.
- The MnO4- ions in KMnO4 gain electrons from SO2 and get reduced to Mn2+ ions.
- On the other hand, SO2 loses electrons and gets oxidized to form sulfuric acid (H2SO4).
- The purple color of the KMnO4 solution fades as the Mn2+ ions are colorless.
- The reaction between SO2 and KMnO4 is a redox reaction, where both oxidation and reduction occur simultaneously.
- The sulfuric acid formed is a strong acid and dissociates into H+ and SO42- ions in solution.
- The overall reaction results in the formation of sulfuric acid, manganese ions, and potassium sulfate.
- This reaction is often used as a qualitative test for the presence of SO2 in a gaseous mixture.

Conclusion:
- When SO2 is passed through acidified KMnO4, the KMnO4 is reduced to Mn2+ ions, and SO2 is oxidized to sulfuric acid.
- The purple color of the KMnO4 solution fades due to the reduction of MnO4- ions.
- This reaction is commonly used to detect the presence of SO2 in a gaseous mixture.