Question

Acidified \(KMnO_4\) oxidizes sulphite to: 

• A. \(SO_3^{2-} \)
• B. \(SO_4^{2-} \)
• C. \(SO_2(g) \)
• D. \(S_2O_8^{2-} \)

Hint:

KMnO_4 in acidic conditions oxidizes sulphite to sulfate.

Answer 1

The Correct Option is D

Solution:

The reaction between acidified potassium permanganate (KMnO₄) and sulphite (SO₃^2-) occurs as an oxidation-reduction (redox) process. In this reaction, KMnO₄ acts as an oxidizing agent, converting the sulphite ion to another form.

The oxidation state of sulphur in SO₃^2- is +4. The goal of the oxidation process is to increase the oxidation state of sulphur. Acidified KMnO₄ effectively oxidizes sulphite ions to peroxodisulfate ions (S₂O₈^2-). This involves the formation of a compound where two sulphur atoms are bonded via an oxygen-oxygen bond, and each sulphur atom is in the +6 oxidation state.

The balanced redox reaction is:

2KMnO₄ + 5SO₃^2- + 6H⁺ → 2Mn²⁺ + 5SO₄^2- + 3H₂O

Correct answer:

S₂O₈^2-