Question

Which of the following occurs with KMnO\(_4\) in neutral medium?

• A. Oxidation of oxalate ion
• B. Precipitation of sulfur from hydrogen sulfide
• C. Oxidation of Fe\(^{2+}\) to Fe\(^{3+}\)
• D. Oxidation of iodide to iodate

Hint:

KMnO\(_4\) in neutral medium oxidizes iodide (\(I^-\)) to iodate (\(IO_3^-\)).

Answer 1

The Correct Option is D

Step 1: Understanding the Oxidizing Nature of KMnO\(_4\) 
- In an acidic medium, KMnO\(_4\) is a strong oxidizing agent.
- In a neutral medium, its oxidizing power decreases but still oxidizes some species.
Step 2: Oxidation Reactions in Neutral Medium 
- KMnO\(_4\) oxidizes I\(^-\) to IO\(_3^-\) in neutral medium:
\[ 2MnO_4^- + I^- + H_2O \rightarrow IO_3^- + MnO_2 + OH^- \] - Other reactions:
- Oxidation of oxalate ion occurs in acidic medium.
- Precipitation of sulfur from \( H_2S \) occurs in acidic medium.
- Fe\(^{2+}\) to Fe\(^{3+}\) oxidation occurs in acidic medium. 
Thus, the correct answer is Oxidation of iodide to iodate.

Answer 2

Potassium permanganate (KMnO₄) acts as a strong oxidizing agent, and its behavior depends on the pH of the medium:

1. In acidic medium: KMnO₄ is reduced to Mn²⁺.
2. In neutral medium: KMnO₄ is reduced to MnO₂ (manganese dioxide).
3. In basic medium: KMnO₄ is reduced to MnO₄²⁻.

In neutral medium, KMnO₄ can oxidize iodide (I⁻) to iodate (IO₃⁻).

Balanced reaction in neutral medium:
3 I⁻ + 2 KMnO₄ + H₂O → 3 IO₃⁻ + 2 MnO₂ + 2 KOH

Here, iodide (I⁻) is oxidized to iodate (IO₃⁻), and KMnO₄ is reduced to MnO₂.

Therefore, the correct process that occurs with KMnO₄ in neutral medium is:
Oxidation of iodide to iodate.