Which of the following act as an oxidizing as well as a reducing agent?

Options

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

Explanation

To determine which of the given compounds can act as both oxidizing and reducing agents, we will analyze each compound based on the oxidation states of their constituent elements.

### Step-by-Step Solution:

1. **Understanding Oxidizing and Reducing Agents**:
- An **oxidizing agent** is a substance that gains electrons (is reduced) while causing another substance to be oxidized (lose electrons).
- A **reducing agent** is a substance that loses electrons (is oxidized) while causing another substance to be reduced (gain electrons).

2. **Analyzing HNO2 (Nitrous Acid)**:
- The oxidation state of nitrogen in HNO2 can be calculated as follows:
- H: +1
- O: -2 (2 oxygen atoms contribute -4)
- Let the oxidation state of N be x.
- The overall charge is 0: \( x + 1 - 4 = 0 \) → \( x = +3 \).
- Nitrogen can have oxidation states ranging from +5 to -3.
- HNO2 can be reduced (gain electrons) to lower oxidation states (like -3) and can also oxidize (lose electrons) to higher oxidation states (like +5).
- **Conclusion**: HNO2 can act as both an oxidizing and reducing agent.

3. **Analyzing H2O2 (Hydrogen Peroxide)**:
- The oxidation state of oxygen in H2O2 is -1.
- Oxygen can exist in various oxidation states (-2, -1, 0, +1, +2).
- H2O2 can be reduced to -2 (as in water) or oxidized to +2 (as in O2).
- **Conclusion**: H2O2 can act as both an oxidizing and reducing agent.

4. **Analyzing H2S (Hydrogen Sulfide)**:
- The oxidation state of sulfur in H2S is -2.
- Sulfur can range from -2 to +6.
- H2S can only be oxidized (to higher oxidation states) but cannot be reduced further (it cannot gain electrons).
- **Conclusion**: H2S can only act as a reducing agent.

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

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

Thus, the answer is **HNO2, H2O2, and SO2**.