In which `SO_(2)` acts as oxidant, while reacting with

Options

A. Acidified `KMnO_(4)`
B. acidified `K_(2)Cr_(2)O_(7)`
C. `H_(2)S`
D. acidified `C_(2)H_(5)OH`

Answer

To determine in which reaction sulfur dioxide (SO₂) acts as an oxidant, we need to analyze its behavior in the presence of various reagents. Let's break down the question step by step.

### Step 1: Identify the Reagents
The reagents mentioned in the question are:
1. Acidified potassium permanganate (KMnO₄)
2. Acidified potassium dichromate (K₂Cr₂O₇)
3. Hydrogen sulfide (H₂S)
4. Acidified ethanol

### Step 2: Analyze the Reactions
We need to analyze how SO₂ interacts with each of these reagents:

1. **Acidified Potassium Permanganate (KMnO₄)**:
- In acidic medium, KMnO₄ is a strong oxidizing agent.
- When SO₂ reacts with KMnO₄, SO₂ acts as a reducing agent, meaning it donates electrons and gets oxidized.

2. **Acidified Potassium Dichromate (K₂Cr₂O₇)**:
- Similar to KMnO₄, K₂Cr₂O₇ is also a strong oxidizing agent in acidic conditions.
- SO₂ again acts as a reducing agent in this reaction.

3. **Hydrogen Sulfide (H₂S)**:
- H₂S is a reducing agent, and when it reacts with SO₂, SO₂ acts as an oxidizing agent.
- In this reaction, SO₂ accepts electrons from H₂S and gets reduced.

4. **Acidified Ethanol**:
- In the presence of acidified ethanol, SO₂ does not act as an oxidizing agent. Instead, it behaves as a reducing agent.

### Step 3: Conclusion
From the analysis:
- SO₂ acts as an oxidizing agent when reacting with **hydrogen sulfide (H₂S)**.
- In the reactions with acidified potassium permanganate and potassium dichromate, SO₂ acts as a reducing agent.

### Final Answer
Sulfur dioxide (SO₂) acts as an oxidant when reacting with **hydrogen sulfide (H₂S)**.

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