Assertion: Aniline is a weaker base than ammonia.
Reason : Aniline is resonance stabilized.

Answer

To solve the question regarding the assertion and reason provided, we will analyze both statements step by step.

### Step 1: Understand the Assertion
**Assertion:** Aniline is a weaker base than ammonia.

- **Explanation:** Aniline (C6H5NH2) has an amino group (-NH2) attached to a benzene ring. Ammonia (NH3), on the other hand, does not have any such substituent. The basicity of a compound is determined by its ability to donate a lone pair of electrons.

### Step 2: Compare Basicity of Aniline and Ammonia
- **Ammonia:** In ammonia, the lone pair of electrons on the nitrogen atom is readily available for donation, making it a good base.

- **Aniline:** In aniline, the lone pair of electrons on the nitrogen can participate in resonance with the benzene ring. This resonance delocalizes the electron density, making the lone pair less available for donation compared to ammonia.

### Step 3: Conclusion on Basicity
- Since the lone pair in aniline is less available due to resonance stabilization, aniline is indeed a weaker base than ammonia. Thus, the assertion is **true**.

### Step 4: Understand the Reason
**Reason:** Aniline is resonance stabilized.

- **Explanation:** The presence of the benzene ring allows for resonance, which stabilizes the aniline molecule. This stabilization reduces the electron density on the nitrogen atom, making it less basic.

### Step 5: Conclusion on Reason
- The reason provided is also **true**, as resonance does stabilize aniline, but it does not serve as the correct explanation for why aniline is a weaker base than ammonia. The basicity comparison is primarily due to the availability of the lone pair of electrons.

### Final Conclusion
- Both the assertion and reason are true, but the reason is not the correct explanation for the assertion. Therefore, the answer to the question is that both statements are true, but the reason is not the right explanation for the assertion.