Question

Which of the following oxidation reactions of \(\mathrm{KMnO_4}\) occur in acidic medium? \[ \begin{aligned} \text{I. }&\text{Oxidation of oxalic acid} \\ \text{II. }&\text{Oxidation of iodide to iodate} \\ \text{III. }&\text{Precipitation of sulphur from hydrogen sulphide} \end{aligned} \] The correct answer is

• A. I, II, III
• B. II, III only
• C. I, III only
• D. I, II only

Hint:

Acidified \(\mathrm{KMnO_4}\) is a strong oxidizing agent and commonly oxidizes \[ \boxed{ \text{Oxalic acid, } \mathrm{Fe^{2+}}, \mathrm{H_2S}, \text{etc.} } \] whereas oxidation of iodide to iodate is carried out in alkaline medium.

Answer 1

The Correct Option is C

Step 1: Check each reaction. \[ \boxed{\text{I. Oxidation of oxalic acid}} \] This reaction is carried out using acidified \(\mathrm{KMnO_4}\). Hence, Statement I is correct. \[ \boxed{\text{II. Oxidation of iodide to iodate}} \] Oxidation of iodide to iodate occurs in alkaline medium, not acidic medium. Hence, Statement II is incorrect. \[ \boxed{\text{III. Oxidation of } \mathrm{H_2S}} \] Acidified \(\mathrm{KMnO_4}\) oxidizes hydrogen sulphide to sulphur. \[ \mathrm{H_2S \rightarrow S} \] Hence, Statement III is correct. Therefore, \[ \boxed{\text{I and III only}} \] Hence, \[ \boxed{(C)} \] is the correct answer.