Read the passage carefully and answer the Questions.
\( KMnO_4 \) is prepared by the fusion of \( MnO_2 \) with an alkali metal hydroxide and an oxidizing agent like \( KNO_3 \) to give a dark- green manganate ion which disproportionates to give permanganate as follows.
\( 2MnO_2+ 4KOH + O_2→2K_2MnO_4+2H_2O \)
\( 3K_2MnO_4+ 4H^+→2KMnO_4 + MnO_2 + 2H_2O \)
On heating \( KMnO_4 \) decomposes at 513 K to give \( K_2MnO_4 \). Permanganate ion is tetrahedral and diamagnetic. Acidified \( KMnO_4 \) acts as a strong oxidizing agent which oxidizes oxalic acid, ferrous ions, nitrite ion and iodides.
Reaction of iodide ion (\( I^- \)) with \( KMnO_4 \) will.....
Answer & explanation
Correct answer: option 1
The correct answer is Option (1) → liberate \(I_2\) in acidic solution
What permanganate turns into, and how far it oxidises the reducing agent, depends on the hydrogen ion concentration of the solution. In acid it is reduced to \( \ce{Mn^2+} \) (5 electrons); in neutral or faintly alkaline solution it stops at \( \ce{MnO2} \) (3 electrons).
In acidic solution iodide ions are oxidised only as far as free iodine; in neutral or faintly alkaline solution the oxidation goes on to the iodate ion.
Why the other options are incorrect
Option (2) produce \({IO_3}^-\) in acidic solution — Incorrect. Iodate is the product in neutral or faintly alkaline solution; in acid the oxidation stops at iodine.
Option (3) liberate \(I_2\) in neutral or mild alkaline solution — Incorrect. The medium is right for a different product: in neutral or faintly alkaline solution iodide is oxidised past iodine to \( \ce{IO3^-} \).
Option (4) produce \(I_2O_4\) in neutral or mild alkaline solution — Incorrect. Diiodine tetroxide is not formed in solution; the product in this medium is the iodate ion.
Note: It seems that there is a mistake in the original NTA paper. The second equation of the passage is printed as 3K2MnO4 + 4H+ → 2KMnO4 + MnO2 + 2H2O, in which the charges do not balance; it should be 3MnO42− + 4H+ → 2MnO4− + MnO2 + 2H2O.
NCERT (2026-27 edition):
Oxides and Oxoanions of Metals – …
