In which of the following salts only cationic hydrolysis is involved ?

Options

A. `CH_3COONH_4`
B. `CH_3COONa`
C. `NH_4Cl`
D. `Na_2SO_4`

Answer

To determine which of the given salts undergoes only cationic hydrolysis, we need to analyze the hydrolysis behavior of the cations and anions present in each salt.

### Step-by-Step Solution:

1. **Understanding Hydrolysis**: Hydrolysis is the reaction of a salt with water. It can involve either the cation or the anion or both. Cationic hydrolysis occurs when the cation of the salt reacts with water to produce an acidic solution, while anionic hydrolysis occurs when the anion reacts with water to produce a basic solution.

2. **Identifying the Salts**: The salts to be analyzed are:
- CH3COONH4 (Ammonium acetate)
- NH4Cl (Ammonium chloride)
- Na2SO4 (Sodium sulfate)
- KNO3 (Potassium nitrate)

3. **Analyzing Each Salt**:
- **CH3COONH4**:
- Cation: NH4+ (Ammonium ion)
- Anion: CH3COO- (Acetate ion)
- NH4+ can undergo hydrolysis to form NH3 and H3O+, while CH3COO- can undergo hydrolysis to form CH3COOH and OH-. Therefore, both cationic and anionic hydrolysis occur.

- **NH4Cl**:
- Cation: NH4+
- Anion: Cl-
- NH4+ can hydrolyze to produce NH3 and H3O+, while Cl- does not hydrolyze because it is the conjugate base of a strong acid (HCl). Thus, only cationic hydrolysis occurs.

- **Na2SO4**:
- Cation: Na+
- Anion: SO4^2-
- Na+ does not hydrolyze because it is the conjugate base of a strong acid (NaOH). SO4^2- does not hydrolyze significantly either, as it is the conjugate base of a strong acid (H2SO4). Therefore, no hydrolysis occurs.

- **KNO3**:
- Cation: K+
- Anion: NO3-
- Similar to Na+, K+ does not hydrolyze, and NO3- does not hydrolyze significantly as it is the conjugate base of a strong acid (HNO3). Therefore, no hydrolysis occurs.

4. **Conclusion**: Among the salts analyzed, only **NH4Cl** undergoes cationic hydrolysis exclusively.

### Final Answer:
The salt in which only cationic hydrolysis is involved is **NH4Cl**.