Question

In the reaction between moist SO₂ and acidified permanganate solution:

• A. SO₂ is oxidised to SO₄²⁻, MnO₄⁻ is reduced to Mn²⁺
• B. SO₂ is reduced to S, MnO₄⁻ is oxidised to MnO₄
• C. SO₂ is oxidised to SO₃²⁻, MnO₄⁻ is reduced to MnO₂
• D. SO₂ is reduced to H₂S, MnO₄⁻ is oxidised to MnO₄

Hint:

The reaction shows SO₂ oxidation to SO₄²⁻ and MnO₄⁻ reduction to Mn²⁺.

Answer 1

The Correct Option is A

The question pertains to the redox reaction between sulfur dioxide (\(\text{SO}_2\)) and acidified permanganate ions (\(\text{MnO}_4^-\). To solve this, we need to understand the oxidation and reduction processes occurring in the reaction:

1. The reaction involves two half-reactions: one for the oxidation of \(\text{SO}_2\) and another for the reduction of \(\text{MnO}_4^-.\)
2. Oxidation: \(\text{SO}_2\) is oxidized to \(\text{SO}_4^{2-}\). In this process, sulfur's oxidation state increases from +4 in \(\text{SO}_2\) to +6 in \(\text{SO}_4^{2-}\).
3. Reduction: \(\text{MnO}_4^-\) (in the presence of acid) is reduced to \(\text{Mn}^{2+}\). Manganese's oxidation state decreases from +7 in \(\text{MnO}_4^-\) to +2 in \(\text{Mn}^{2+}\).
4. Balance the half-reactions considering the number of electrons transferred and combine them to get the overall reaction.

Given these explanation points, the correct option is: SO₂ is oxidised to SO₄²⁻, MnO₄⁻ is reduced to Mn²⁺.

The other options are incorrect because:

• SO₂ is reduced to S, MnO₄⁻ is oxidised to MnO₄: This does not represent a legitimate redox reaction. SO₂ is generally oxidized, not reduced to elemental sulfur.
• SO₂ is oxidised to SO₃²⁻, MnO₄⁻ is reduced to MnO₂: SO₂ oxidation results in SO₄²⁻ rather than SO₃²⁻, and MnO₄⁻ reduction in acid medium yields Mn²⁺, not MnO₂.
• SO₂ is reduced to H₂S, MnO₄⁻ is oxidised to MnO₄: This configuration is incorrect for reactions with permanganate in acidic media, as this medium oxidizes rather than reduces sulfur compounds like SO₂.

Hence, the step-by-step analysis confirms why the correct answer is the stated option.