The number of amines having `pK_(b)` less than `C_(6)H_(5)NH_(2)` among the following is
`P-CH_(3) C_(6)H_(5)NH_(2), o-CH_(3)C_(6)H_(4)NH_(2), m-CH_(3)C_(6)H_(4)NH_(2), C_(6)H_(5)N (CH_(3)) _(2), C_(6)H_(5)NHCH_(3), p-NO_(2)C_(6)H_(4)NH_(2), p-CIC_(6)H_(4)NH_(2), C_(6)H_(5)CH_(2)NH_(2)`

Explanation

To determine the number of amines with a `pK_b` value less than that of aniline (`C6H5NH2`), we need to analyze the basic strength of each amine listed. The basic strength of an amine is influenced by the presence of electron-donating or electron-withdrawing groups, as well as the localization of the lone pair on the nitrogen atom.

### Step-by-step Solution:

1. **Identify the reference compound**: The reference compound is aniline (`C6H5NH2`). We need to find out which of the listed amines have a higher basic strength than aniline, as those will have a `pK_b` value less than that of aniline.

2. **Analyze each compound**:
- **P-CH3C6H5NH2**: The presence of a methyl group (CH3) at the para position is an electron-donating group. This increases the electron density on the nitrogen, making it more basic than aniline. **(More basic)**

- **o-CH3C6H4NH2**: The methyl group is in the ortho position. While it is an electron-donating group, the ortho effect reduces the basicity of this amine compared to aniline. **(Less basic)**

- **m-CH3C6H4NH2**: The methyl group is in the meta position, which does not have the ortho effect. This compound is more basic than aniline due to the electron-donating effect of the methyl group. **(More basic)**

- **C6H5N(CH3)2**: This compound has two methyl groups attached to nitrogen. The electron-donating effect of both methyl groups significantly increases the basicity, making it more basic than aniline. **(More basic)**

- **C6H5NHCH3**: This compound has a methyl group attached to the nitrogen. The electron-donating effect of the methyl group increases the basicity, making it more basic than aniline. **(More basic)**

- **p-NO2C6H4NH2**: The nitro group (NO2) is a strong electron-withdrawing group, which decreases the basicity of the amine. Therefore, this compound is less basic than aniline. **(Less basic)**

- **p-ClC6H4NH2**: The chloro group (Cl) is also an electron-withdrawing group, which decreases the basicity of the amine. This compound is less basic than aniline. **(Less basic)**

- **C6H5CH2NH2**: The benzylamine has the nitrogen lone pair localized and is not involved in resonance with the aromatic ring, making it more basic than aniline. **(More basic)**

3. **Count the compounds**: From the analysis, the compounds that are more basic than aniline are:
- P-CH3C6H5NH2
- m-CH3C6H4NH2
- C6H5N(CH3)2
- C6H5NHCH3
- C6H5CH2NH2

Thus, there are **5 compounds** with a `pK_b` less than that of aniline.

### Final Answer:
The number of amines having `pK_b` less than `C6H5NH2` is **5**.