Which of the following behaves as both oxidising and reducing agents ?

Explanation

To determine which of the given compounds behaves as both an oxidizing and reducing agent, we will analyze each option based on the oxidation states of the elements involved.

### Step-by-Step Solution:

1. **Identify the Compounds**:
We have four options to analyze:
- A) H₂SO₄
- B) SO₂
- C) H₂O
- D) HNO₃

2. **Analyze Option A: H₂SO₄**:
- Determine the oxidation state of sulfur (S) in H₂SO₄.
- The oxidation state can be calculated as follows:
\[ 2(+1) + x + 4(-2) = 0 \implies 2 + x - 8 = 0 \implies x = +6 \]
- Since sulfur is in the +6 oxidation state, it cannot act as a reducing agent (it cannot be oxidized further). Thus, H₂SO₄ is an oxidizing agent but not a reducing agent.

**Conclusion for A**: Not both oxidizing and reducing.

3. **Analyze Option B: SO₂**:
- Determine the oxidation state of sulfur (S) in SO₂.
- The oxidation state can be calculated as follows:
\[ x + 2(-2) = 0 \implies x - 4 = 0 \implies x = +4 \]
- Sulfur can either gain electrons (to become +3) or lose electrons (to become +6). Therefore, SO₂ can act as both an oxidizing agent and a reducing agent.

**Conclusion for B**: This is both an oxidizing and reducing agent.

4. **Analyze Option C: H₂O**:
- Determine the oxidation states of hydrogen (H) and oxygen (O) in H₂O.
- The oxidation states are:
- H: +1
- O: -2
- These oxidation states are fixed and do not allow H₂O to act as either an oxidizing or reducing agent.

**Conclusion for C**: Not both oxidizing and reducing.

5. **Analyze Option D: HNO₃**:
- Determine the oxidation state of nitrogen (N) in HNO₃.
- The oxidation state can be calculated as follows:
\[ +1 + x + 3(-2) = 0 \implies 1 + x - 6 = 0 \implies x = +5 \]
- Nitrogen in HNO₃ is in the +5 oxidation state, which means it can only act as an oxidizing agent and cannot be reduced further.

**Conclusion for D**: Not both oxidizing and reducing.

### Final Answer:
The only compound that behaves as both an oxidizing and reducing agent is **Option B: SO₂**.

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