Assertion: n-Propylamine has higher boiling point than trimethylamine.
Reason : Among n-propylamine molecules, there is hydrogen bonding but there is no hydrogen bonding in trimethylamine.

Answer

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

**Assertion:** n-Propylamine has a higher boiling point than trimethylamine.
**Reason:** Among n-propylamine molecules, there is hydrogen bonding but there is no hydrogen bonding in trimethylamine.

### Step-by-Step Solution:

1. **Identify the Structures:**
- n-Propylamine (C3H9N) has the structure: CH3-CH2-CH2-NH2.
- Trimethylamine (C3H9N) has the structure: (CH3)3N.

2. **Understand Boiling Points:**
- The boiling point of a substance is influenced by the types of intermolecular forces present. Stronger intermolecular forces typically lead to higher boiling points.

3. **Analyze Intermolecular Forces:**
- n-Propylamine can form hydrogen bonds due to the presence of the -NH2 group. Hydrogen bonding occurs when a hydrogen atom is bonded to a highly electronegative atom (like nitrogen) and is attracted to another electronegative atom.
- Trimethylamine, on the other hand, does not have hydrogen bonding because the nitrogen is bonded to three carbon atoms and does not have a hydrogen atom available for bonding.

4. **Compare the Forces:**
- In n-Propylamine, the presence of hydrogen bonding leads to stronger intermolecular attractions compared to the weak Van der Waals forces present in trimethylamine.

5. **Conclusion:**
- Since n-Propylamine has stronger hydrogen bonding, it will have a higher boiling point than trimethylamine, which lacks hydrogen bonding.

6. **Evaluate Assertion and Reason:**
- Both the assertion and the reason are true. The reason correctly explains why n-Propylamine has a higher boiling point than trimethylamine.

### Final Answer:
Both the assertion and reason are true, and the reason correctly explains the assertion.