Q. The number of moles of KMnO₄ that will be needed to react with one mole of sulphite ion in acidic solution is
A) 4/5
B) 2/5
C) 1
D) 3/5
Explanation
[Solution from source] SO₃²⁻ → SO₄²⁻ loses 2 electrons, while MnO₄⁻ → Mn²⁺ gains 5 in acidic medium. So 1 mol sulphite needs 2/5 mol KMnO₄. 4/5 counts the sulphite change twice. Answer (2).
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.