Assertion: The value of van der Waals constant a is larger for ammonia than for nitrogen.
Reason: Hydrogen bonding is present in ammonia.

Options

A. If both assertion and reason are correct and reason is correct explanation for assertion
B. If both assertion and reason are correct and reason is not correct explanation for assertion
C. If assertion is correct but reason is incorrect
D. If assertion and reason are both incorreect.

Explanation

To solve the question, we need to analyze the assertion and the reason provided.

### Step-by-Step Solution:

1. **Understanding the Assertion**:
- The assertion states that the value of the van der Waals constant 'a' is larger for ammonia (NH₃) than for nitrogen (N₂).
- The van der Waals constant 'a' is a measure of the attraction between particles in a gas. A higher value of 'a' indicates stronger intermolecular attractions.

2. **Understanding the Reason**:
- The reason given is that hydrogen bonding is present in ammonia.
- Hydrogen bonding occurs when hydrogen is bonded to a highly electronegative atom (like nitrogen, oxygen, or fluorine), leading to strong intermolecular attractions.

3. **Analyzing Ammonia (NH₃)**:
- Ammonia has hydrogen atoms bonded to a nitrogen atom, which is electronegative. This leads to the formation of hydrogen bonds between ammonia molecules.
- The presence of hydrogen bonding results in stronger intermolecular forces compared to gases that do not exhibit hydrogen bonding.

4. **Analyzing Nitrogen (N₂)**:
- Nitrogen is a diatomic molecule and does not exhibit hydrogen bonding. The intermolecular forces in nitrogen are primarily weak van der Waals forces (London dispersion forces).
- Therefore, nitrogen has a lower value of 'a' compared to ammonia.

5. **Conclusion**:
- Since ammonia has stronger intermolecular attractions due to hydrogen bonding, the value of van der Waals constant 'a' is indeed larger for ammonia than for nitrogen.
- Both the assertion and the reason are true, and the reason correctly explains the assertion.

### Final Answer:
- The assertion is true, and the reason is also true. The reason is the correct explanation for the assertion.