Which of the following reagent can act as reducing agent with `SO_(2)` :-

Options

A. `Cl_(2)`
B. `KMnO_(4)`
C. `HNO_(3)`
D. `H_(2)S`

Answer

To determine which reagent can act as a reducing agent with sulfur dioxide (SO₂), we need to analyze the oxidation states of the elements involved and the properties of the reagents provided.

### Step-by-Step Solution:

1. **Identify the Oxidation State of Sulfur in SO₂:**
- In sulfur dioxide (SO₂), sulfur (S) has an oxidation state of +4.

2. **Understanding Reducing Agents:**
- A reducing agent is a substance that can donate electrons and thereby reduce another substance. In the process, the reducing agent itself gets oxidized (i.e., its oxidation state increases).

3. **Analyzing the Given Reagents:**
- We need to evaluate each reagent to see if it can reduce the +4 oxidation state of sulfur in SO₂.

4. **Evaluating Each Reagent:**
- **Cl₂ (Chlorine):** Chlorine is a strong oxidizing agent and cannot reduce sulfur dioxide. It cannot act as a reducing agent.
- **Cl₄ (Chlorine Tetroxide):** Similar to Cl₂, Cl₄ is also a strong oxidizing agent and cannot reduce sulfur dioxide.
- **HNO₃ (Nitric Acid):** Nitric acid contains nitrogen in a high oxidation state (+5), which makes it a strong oxidizing agent. It cannot act as a reducing agent.
- **MnO₄⁻ (Permanganate Ion):** Manganese in permanganate has an oxidation state of +7. It is also a strong oxidizing agent and cannot increase its oxidation state further.
- **H₂S (Hydrogen Sulfide):** In H₂S, sulfur has an oxidation state of -2. It can increase its oxidation state to +4 (or higher) and can therefore act as a reducing agent.

5. **Conclusion:**
- The only reagent that can act as a reducing agent with SO₂ is **H₂S (Hydrogen Sulfide)**. The reaction can be represented as follows:
\[ \text{H}_2\text{S} + \text{SO}_2 \rightarrow \text{S} + 2 \text{H}_2\text{O} \]
- In this reaction, H₂S reduces the sulfur in SO₂ from +4 to 0, while H₂S itself gets oxidized from -2 to 0.

### Final Answer:
The reagent that can act as a reducing agent with SO₂ is **H₂S (Hydrogen Sulfide)**.

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