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 substances the dissociation of ammonium hydroxide (NH₄OH) will be minimum, we need to consider the common ion effect and the nature of the substances given in the options.

### Step 1: Understand the dissociation of NH₄OH
Ammonium hydroxide (NH₄OH) is a weak base and dissociates in water as follows:
\[ \text{NH}_4\text{OH} \rightleftharpoons \text{NH}_4^+ + \text{OH}^- \]

### Step 2: Identify the common ion effect
The common ion effect states that the dissociation of a weak electrolyte is suppressed when a strong electrolyte that provides a common ion is added to the solution. In this case, the common ion is either NH₄⁺ or OH⁻.

### Step 3: Analyze each option
1. **Sodium Hydroxide (NaOH)**:
- NaOH is a strong base and dissociates completely into Na⁺ and OH⁻ ions.
- The presence of OH⁻ from NaOH will suppress the dissociation of NH₄OH due to the common ion effect.

2. **Water (H₂O)**:
- Water is a very weak electrolyte and does not provide any significant concentration of ions.
- Therefore, it does not exhibit a common ion effect on NH₄OH.

3. **Ammonium Chloride (NH₄Cl)**:
- NH₄Cl dissociates into NH₄⁺ and Cl⁻ ions.
- The NH₄⁺ ion is a common ion with NH₄OH, which will suppress its dissociation due to the common ion effect.

4. **Sodium Chloride (NaCl)**:
- NaCl dissociates into Na⁺ and Cl⁻ ions.
- There is no common ion with NH₄OH, so it does not suppress its dissociation.

### Step 4: Conclusion
From the analysis:
- The dissociation of NH₄OH will be minimum in the presence of **Sodium Hydroxide (NaOH)** and **Ammonium Chloride (NH₄Cl)** due to the common ion effect.

Thus, the correct answers are:
- **Sodium Hydroxide (NaOH)** and **Ammonium Chloride (NH₄Cl)**.