Potassium Permanganate
When potassium permanganate acts as an oxidising agent in acidic medium, to which oxidation state is the manganese reduced from its initial plus seven state?
Select the correct option:
Solution
+2
The product of permanganate reduction depends on the medium of the reaction. In acidic medium, the permanganate ion MnO_4^-, in which manganese is in the +7 state, is reduced by gaining five electrons to give the nearly colourless Mn^2+ ion, in which manganese is in the +2 state: MnO_4^- + 8H^+ + 5e^- → Mn^2+ + 4H_2O. This five-electron change makes permanganate a powerful oxidant in acidic conditions. The option +3 is not a stable reduction product of permanganate in acid. The option +4 corresponds to MnO_2, which forms in neutral or faintly alkaline medium. The option +6 corresponds to the green manganate ion MnO_4^2-, formed in strongly alkaline medium. Knowing the medium-dependent products of permanganate is a standard NCERT d-block fact essential for redox titrations. Plausibility check: the disappearance of the purple colour to give almost colourless Mn^2+ in acidic titrations confirms reduction to the +2 state.
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About This Question
- Subject
- chemistry
- Chapter
- d- and f-block elements
- Topic
- potassium permanganate
- Difficulty
- Easy
- Year
- 2025
Solution
Correct Answer:
+2
The product of permanganate reduction depends on the medium of the reaction. In acidic medium, the permanganate ion MnO_4^-, in which manganese is in the +7 state, is reduced by gaining five electrons to give the nearly colourless Mn^2+ ion, in which manganese is in the +2 state: MnO_4^- + 8H^+ + 5e^- → Mn^2+ + 4H_2O. This five-electron change makes permanganate a powerful oxidant in acidic conditions. The option +3 is not a stable reduction product of permanganate in acid. The option +4 corresponds to MnO_2, which forms in neutral or faintly alkaline medium. The option +6 corresponds to the green manganate ion MnO_4^2-, formed in strongly alkaline medium. Knowing the medium-dependent products of permanganate is a standard NCERT d-block fact essential for redox titrations. Plausibility check: the disappearance of the purple colour to give almost colourless Mn^2+ in acidic titrations confirms reduction to the +2 state.
This easy difficulty chemistry question is from the chapter d- and f-block elements, covering the topic of potassium permanganate. It appeared in the 2025 exam.
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