Which of the following compounds acts both as an oxidising as wll as a reducing agent?

Options

A. `HNO_(2)`
B. `H_(2)O_(2)`
C. `H_(2)S`
D. `SO_(2)`

Answer

To determine which of the given compounds acts both as an oxidizing agent and a reducing agent, we will analyze each compound's oxidation states and their ability to either gain or lose electrons.

### Step-by-Step Solution:

1. **Analyze HNO2 (Nitrous Acid)**:
- The oxidation state of nitrogen in HNO2 is +3.
- Nitrogen can exist in various oxidation states, ranging from -3 to +5.
- Since HNO2 can either accept electrons (be reduced) or donate electrons (be oxidized), it can act as both an oxidizing agent and a reducing agent.
- **Conclusion**: HNO2 can act as both.

2. **Analyze H2O2 (Hydrogen Peroxide)**:
- The oxidation state of oxygen in H2O2 is -1.
- Oxygen can have oxidation states ranging from -2 to +2.
- H2O2 can either gain electrons (be reduced) or lose electrons (be oxidized).
- **Conclusion**: H2O2 can also act as both.

3. **Analyze H2S (Hydrogen Sulfide)**:
- The oxidation state of sulfur in H2S is -2.
- Sulfur can have oxidation states ranging from -2 to +6.
- H2S can only be oxidized (losing electrons) but cannot be reduced (gaining electrons).
- **Conclusion**: H2S cannot act as both; it only acts as a reducing agent.

4. **Analyze SO2 (Sulfur Dioxide)**:
- The oxidation state of sulfur in SO2 is +4.
- Sulfur can exist in oxidation states from -2 to +6.
- SO2 can either gain electrons (be reduced) or lose electrons (be oxidized).
- **Conclusion**: SO2 can act as both an oxidizing agent and a reducing agent.

### Final Conclusion:
The compounds that act as both oxidizing and reducing agents are:
- HNO2
- H2O2
- SO2

Thus, the correct options are A (HNO2), B (H2O2), and D (SO2).