JEE Chemistry 2025 Question with Solution

Given: The reactions to be checked are oxidation reactions in acidic medium for both $K_2Cr_2O_7$ and $KMnO_4$.

Find: Which listed reactions are carried out by both oxidizing agents.

Both $K_2Cr_2O_7$ and $KMnO_4$ are strong oxidizing agents in acidic medium. We examine each reaction from the solution:

1. A. $I^- \rightarrow I_2$ Both oxidizing agents can oxidize iodide to iodine.

2. B. $S^{2-} \rightarrow S$ Both oxidizing agents can oxidize sulfide to sulfur.

3. C. $Fe^{2+} \rightarrow Fe^{3+}$ Both oxidizing agents can oxidize ferrous ion to ferric ion.

4. D. $I^- \rightarrow IO_3^-$ This is a stronger oxidation. The solution states that $KMnO_4$ can do this, but $K_2Cr_2O_7$ does not carry out this oxidation completely in acidic medium.

5. E. $S_2O_3^{2-} \rightarrow SO_4^{2-}$ The solution states this is not consistently carried out by both reagents under similar acidic conditions.

Therefore, the reactions common to both are A, B and C only.

The correct option is B.

Note: The answer key marks option $(1)$, but the worked solution concludes A, B and C only. As per the solution, the answer is taken as B.

Given: Oxidation reactions involving $K_2Cr_2O_7$ and $KMnO_4$ in acidic medium.

Find: The set of reactions performed by both reagents.

Step 1: Recall the oxidizing behaviour in acidic medium.

Both act as strong oxidizing agents.

Step 2: Check each transformation.

• $I^- \rightarrow I_2$: possible with both.
• $S^{2-} \rightarrow S$: possible with both.
• $Fe^{2+} \rightarrow Fe^{3+}$: possible with both.
• $I^- \rightarrow IO_3^-$: not common to both under standard acidic conditions according to the solution.
• $S_2O_3^{2-} \rightarrow SO_4^{2-}$: not consistently carried out by both according to the solution.

Step 3: Collect the common reactions. The common set is A, B, C.

Hence the final answer is A, B and C only, so the correct option is B.