In which of the following, dissociation of `NH_(4)OH` will be minimum?

Options

A. NaOH
B. `H_(2)O`
C. `NH_(4)Cl`
D. NaCl

Explanation

To determine in which of the following options the dissociation of `NH4OH` (ammonium hydroxide) will be minimum, we need to analyze the common ion effect. The common ion effect states that the dissociation of a weak electrolyte is suppressed when a strong electrolyte that shares a common ion is added to the solution.

### Step-by-Step Solution:

1. **Identify the Options**: The options given are:
- (1) Sodium Hydroxide (NaOH)
- (2) Water (H2O)
- (3) Ammonium Chloride (NH4Cl)
- (4) Sodium Chloride (NaCl)

2. **Understand the Dissociation of NH4OH**:
- Ammonium hydroxide dissociates in water as follows:
\[ NH_4OH \rightleftharpoons NH_4^+ + OH^- \]

3. **Analyze Each Option**:
- **Sodium Hydroxide (NaOH)**: When NaOH is added, it dissociates completely to give Na+ and OH-. The increase in OH- concentration will shift the equilibrium to the left, but it does not introduce a common ion with NH4OH.
- **Water (H2O)**: Adding water does not affect the dissociation of NH4OH as it does not introduce any ions.
- **Ammonium Chloride (NH4Cl)**: NH4Cl dissociates to give NH4+ and Cl-. The presence of NH4+ (a common ion) will suppress the dissociation of NH4OH due to the common ion effect.
- **Sodium Chloride (NaCl)**: NaCl dissociates into Na+ and Cl-. Neither of these ions is a common ion with NH4OH, so it will not significantly affect its dissociation.

4. **Conclusion**: Among the options, the addition of **Ammonium Chloride (NH4Cl)** introduces a common ion (NH4+), which will minimize the dissociation of NH4OH due to the common ion effect.

### Final Answer:
The dissociation of `NH4OH` will be minimum in the presence of **Ammonium Chloride (NH4Cl)**.