Which of the following acts as an oxidising as well as reducing agent ?

Options

A. `Na_(2)O`
B. `H_2SO_4`
C. `HNO_3`
D. `HNO_2`

Answer

To determine which compound acts as both an oxidizing and reducing agent, we need to analyze the oxidation states of the elements in each compound. Here’s a step-by-step solution:

### Step 1: Identify the oxidation states of elements in each compound.

1. **Na2O**:
- Sodium (Na) has an oxidation state of +1.
- Oxygen (O) has an oxidation state of -2.

2. **H2SO4**:
- Sulfur (S) has an oxidation state of +6.
- Hydrogen (H) has an oxidation state of +1.
- Oxygen (O) has an oxidation state of -2.

3. **HNO3**:
- Nitrogen (N) has an oxidation state of +5.
- Hydrogen (H) has an oxidation state of +1.
- Oxygen (O) has an oxidation state of -2.

4. **HNO2**:
- Nitrogen (N) has an oxidation state of +3.
- Hydrogen (H) has an oxidation state of +1.
- Oxygen (O) has an oxidation state of -2.

### Step 2: Determine the maximum and minimum oxidation states for each element.

- **Na2O**: Sodium can only be reduced from +1 to 0 (Na^0) and cannot be oxidized further. Thus, it can only act as an oxidizing agent.

- **H2SO4**: Sulfur is at its maximum oxidation state of +6 and cannot be oxidized further. It can only be reduced, so it cannot act as both an oxidizing and reducing agent.

- **HNO3**: Nitrogen is at its maximum oxidation state of +5. It can only be reduced to a lower oxidation state but cannot be oxidized further. Thus, it can only act as an oxidizing agent.

- **HNO2**: Nitrogen is at +3 oxidation state. It can be oxidized to +4 or +5 (acting as a reducing agent) and can also be reduced to +2, +1, 0, or even negative states (acting as an oxidizing agent). Therefore, HNO2 can act as both an oxidizing and reducing agent.

### Step 3: Conclusion

Based on the analysis, the compound that acts as both an oxidizing and reducing agent is **HNO2**.

### Final Answer:
The answer is **HNO2**.

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