Assertion : p-nitroaniline is a weaker base than p-toluidine.
Reason: The electron donating `-NO_(2)` group in p-nitroaniline makes it a weaker base.

Answer

To solve the assertion and reason question regarding p-nitroaniline and p-toluidine, we need to analyze the basicity of both compounds based on their structures and the effects of their substituents.

### Step 1: Understand the Structures
- **p-Nitroaniline** has a nitro group (-NO2) and an amino group (-NH2) attached to a benzene ring.
- **p-Toluidine** has a methyl group (-CH3) and an amino group (-NH2) attached to a benzene ring.

### Step 2: Identify the Nature of the Groups
- The **nitro group** is an electron-withdrawing group due to its strong -I (inductive) and -M (mesomeric) effects. This means it pulls electron density away from the benzene ring and the amino group.
- The **methyl group** is an electron-donating group due to its +I (inductive) effect, which pushes electron density towards the benzene ring and the amino group.

### Step 3: Analyze Basicity
- Basicity in amines is largely determined by the availability of the lone pair of electrons on the nitrogen atom. The more electron density on the nitrogen, the more readily it can donate its lone pair, thus acting as a stronger base.
- In p-nitroaniline, the electron-withdrawing effect of the nitro group decreases the electron density on the nitrogen atom, making it less able to donate its lone pair. Therefore, it is a weaker base.
- In p-toluidine, the electron-donating effect of the methyl group increases the electron density on the nitrogen atom, making it more capable of donating its lone pair. Thus, it is a stronger base.

### Step 4: Conclusion
- The assertion that p-nitroaniline is a weaker base than p-toluidine is **true**.
- The reason given states that the electron-donating -NO2 group in p-nitroaniline makes it a weaker base, which is **false** because the nitro group is actually electron-withdrawing.

### Final Answer
- Assertion: True
- Reason: False