Assertion : Boiling point of p-nitrophenol is greater than that of o-nitrophenol.
Reason : There is intramolecular hydrogen bonding in p-nitrophenol and intermolecular hydrogen bonding in o-nitrophenol.

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

Explanation

To solve the question regarding the boiling points of p-nitrophenol and o-nitrophenol, we will analyze the assertion and reason provided.

### Step-by-Step Solution:

1. **Understanding the Assertion**:
- The assertion states that the boiling point of p-nitrophenol is greater than that of o-nitrophenol.
- This is a claim that we need to evaluate based on the molecular structures and bonding present in both compounds.

2. **Analyzing the Structures**:
- **p-Nitrophenol**: In p-nitrophenol, the nitro group (-NO2) is positioned at the para position relative to the hydroxyl group (-OH) on the benzene ring.
- **o-Nitrophenol**: In o-nitrophenol, the nitro group is at the ortho position relative to the hydroxyl group.

3. **Hydrogen Bonding**:
- **p-Nitrophenol**: The distance between the -OH group and the -NO2 group is larger, which allows for intermolecular hydrogen bonding between different p-nitrophenol molecules. This type of bonding is generally strong and contributes to a higher boiling point.
- **o-Nitrophenol**: The -OH group and the -NO2 group are closer together, allowing for intramolecular hydrogen bonding. This means that the hydrogen bond forms within the same molecule, which is typically weaker than intermolecular hydrogen bonds.

4. **Comparing Boiling Points**:
- Since p-nitrophenol has strong intermolecular hydrogen bonds, it requires more energy (higher temperature) to break these bonds during boiling, resulting in a higher boiling point.
- Conversely, o-nitrophenol, with its weaker intramolecular hydrogen bonding, has a lower boiling point because less energy is needed to separate the molecules.

5. **Evaluating the Reason**:
- The reason states that there is intramolecular hydrogen bonding in p-nitrophenol and intermolecular hydrogen bonding in o-nitrophenol.
- This statement is incorrect because, as established, p-nitrophenol has intermolecular hydrogen bonding, while o-nitrophenol has intramolecular hydrogen bonding.

6. **Conclusion**:
- The assertion is true: the boiling point of p-nitrophenol is indeed greater than that of o-nitrophenol.
- The reason is false: the bonding types are incorrectly assigned.
- Therefore, the correct answer is that the assertion is true, but the reason is false.

### Final Answer:
- The assertion is true, and the reason is false.