Assertion : `HNO_(2)` can act both as a reducing agent and an oxidising agent.
Reason : In `HNO_(2)`, oxidation state of nitrogen is +3 which can change from -3 to +5.

Options

A. If both assertion and reason are true and reason is the correct explanation of assertion.
B. If both assertion and reason are true but reason is not the correct explanation of assertion.
C. If assertion is true but reason is false.
D. If both assertion and reason are false.

Answer

To solve the assertion-reason question regarding the behavior of \( HNO_2 \) (nitrous acid) as both a reducing agent and an oxidizing agent, we can break down the solution into clear steps:

### Step-by-Step Solution:

1. **Identify the Assertion and Reason**:
- **Assertion**: \( HNO_2 \) can act both as a reducing agent and an oxidizing agent.
- **Reason**: In \( HNO_2 \), the oxidation state of nitrogen is +3, which can change from -3 to +5.

2. **Calculate the Oxidation State of Nitrogen in \( HNO_2 \)**:
- The formula for \( HNO_2 \) consists of one hydrogen (H), one nitrogen (N), and two oxygens (O).
- Assign oxidation states:
- Hydrogen (H) = +1
- Oxygen (O) = -2
- Let the oxidation state of nitrogen be \( x \).
- The overall charge of the molecule is neutral (0), so we can set up the equation:
\[ x + 1 + 2(-2) = 0 \]
- Simplifying this gives:
\[ x + 1 - 4 = 0 \implies x - 3 = 0 \implies x = +3 \]
- Thus, the oxidation state of nitrogen in \( HNO_2 \) is +3.

3. **Determine the Range of Oxidation States for Nitrogen**:
- Nitrogen can exhibit various oxidation states. The highest oxidation state is +5, and the lowest is -3.
- Therefore, nitrogen can change from +3 to +5 (losing electrons) or from +3 to -3 (gaining electrons).

4. **Explain the Dual Role of \( HNO_2 \)**:
- **As a Reducing Agent**: When nitrogen in \( HNO_2 \) goes from +3 to -3, it gains electrons, thus acting as a reducing agent.
- **As an Oxidizing Agent**: When nitrogen goes from +3 to +5, it loses electrons, thus acting as an oxidizing agent.

5. **Conclusion**:
- Since the oxidation state of nitrogen in \( HNO_2 \) can change in both directions (from +3 to +5 and from +3 to -3), the assertion that \( HNO_2 \) can act as both a reducing agent and an oxidizing agent is true.
- The reason provided is also true and correctly explains the assertion.

### Final Answer:
Both the assertion and reason are true, and the reason is the correct explanation of the assertion.