JEE Main 2022 · 25 July · morning · Single correct · +4 / −1
The reaction of H₂ O₂ with potassium permanganate in acidic medium leads to the formation of mainly :
- (a) Mn²⁺
- (b) Mn⁴⁺
- (c) Mn³⁺
- (d) Mn⁶⁺
Answer and solution
Answer (a) Mn²⁺
Solution
Chemistry ma’am · 3 steps
In acid, permanganate grabs five electrons and drops all the way from +7 to Mn²⁺.
- Who does what. KMnO₄ is the oxidising agent, with Mn in the +7 state. Here H₂O₂ acts as a reducing agent: its oxygen goes from -1 to 0 and leaves as O₂.
- Medium decides. How far Mn is reduced depends on the medium. In acid, MnO₄⁻ takes 5 electrons and becomes Mn²⁺. In neutral or weakly basic solution it takes 3 and stops at MnO₂ (+4).
2MnO₄⁻ + 5H₂O₂ + 6H⁺ → 2Mn²⁺ + 5O₂ + 8H₂O
- So. Mn goes from +7 to +2, so the main product is Mn²⁺, option (a). That is why the purple colour of permanganate fades in this reaction.
The idea to keep. Permanganate's product depends on the medium: acidic gives Mn²⁺ (5 electrons), neutral or weakly basic gives MnO₂ (3 electrons), strongly basic gives MnO₄²⁻ (1 electron).
Answer from the NTA final answer key. Solution by PrepWiser.