In neutral or mild alkaline solutions, potassium permanganate oxidizes manganous salt (\( Mn^{2+} \)) to.
Answer & explanation
Correct answer: option 1
The correct answer is Option (1) → \(MnO_2\)
Potassium permanganate is an oxidising agent whose product depends on the medium. In acid it is reduced to \( \ce{Mn^2+} \) (+7 to +2). In neutral or faintly alkaline solution it is reduced only to manganese dioxide (+7 to +4):
\( \displaystyle \ce{MnO4^- + 2H2O + 3e- -> MnO2 + 4OH-} \)
A manganous salt is oxidised by it to the same product, \( \ce{MnO2} \) (+2 to +4):
\( \displaystyle \ce{Mn^2+ + 2H2O -> MnO2 + 4H+ + 2e-} \)
To balance electrons, the reduction is taken twice (6 e−) and the oxidation three times (6 e−). Adding them gives the balanced equation, in which the presence of zinc sulphate or zinc oxide catalyses the oxidation:
\( \displaystyle \ce{2MnO4^- + 3Mn^2+ + 2H2O -> 5MnO2 + 4H+} \)
So \( \ce{Mn^2+} \) is oxidised to \( \ce{MnO2} \).
Why the other options are incorrect
Option (2) \(Mn^{2+}\) — Incorrect. This is the starting ion itself; \( \ce{Mn^2+} \) is the product only when permanganate is reduced in acid medium.
Option (3) \({MnO_4}^{-2}\) — Incorrect. Manganate (+6) is formed when \( \ce{MnO2} \) is fused with KOH in air; it is not formed from Mn2+ in neutral solution.
Option (4) \({MnO_4}^-\) — Incorrect. Permanganate (+7) is the oxidising agent here; it cannot oxidise \( \ce{Mn^2+} \) up to its own oxidation state.
NCERT (2026-27 edition):
Oxides and Oxoanions of Metals – …
