Question

$S{O}_2$ behaves as a reducing agent when :

• A. Passed over hot $CuO$.
• B. Mixed with moist $H_{2}S$.
• C. Passes through acidified $KMn{O}_4$ solution.
• D. Passed through $FeS{O}_4$ solution.

Answer 1

The correct option is C Passes through acidified $KMn{O}_4$ solution.

Reaction:
$H_{2}S+S{O}_2\to S_8+H_{2}O$, so $S{O}_2$ acts as oxidising agent.
$5S{O}_2+2KMN{O}_4+2H_{2}O\to 2MNS{O}_4+K_{2}S{O}_4+2H_{2}S{O}_4$
+4 +7 +2 +6
So here it acts as reducing agents.