In analysis of third contains of mixture analysis, solid `NH_(4)Cl` is added prior to `NH_(4)OH` for the following

Options

A. Availability of `Cl^(-)` ions
B. Availability of `NH_(4)^(+)` ions
C. Complete dissociation of `NH_(4)OH`
D. Controlled dissociation of `NH_(4)OH`

Answer

To solve the question regarding the addition of solid \( NH_4Cl \) prior to \( NH_4OH \) in the analysis of a mixture, we can break down the process step by step:

### Step 1: Understanding the Components
- **Identify the compounds**: We have \( NH_4Cl \) (ammonium chloride) and \( NH_4OH \) (ammonium hydroxide).
- **Dissociation in solution**:
- \( NH_4Cl \) dissociates into \( NH_4^+ \) and \( Cl^- \).
- \( NH_4OH \) dissociates into \( NH_4^+ \) and \( OH^- \).

### Step 2: Effect of Adding \( NH_4Cl \)
- When solid \( NH_4Cl \) is added to the solution, it increases the concentration of \( NH_4^+ \) ions in the solution.
- The increased concentration of \( NH_4^+ \) will shift the equilibrium of the dissociation of \( NH_4OH \) according to Le Chatelier's Principle.

### Step 3: Shifting the Equilibrium
- The dissociation of \( NH_4OH \) can be represented as:
\[ NH_4OH \rightleftharpoons NH_4^+ + OH^- \]
- With the addition of \( NH_4Cl \), the concentration of \( NH_4^+ \) increases, causing the equilibrium to shift to the left (backward direction).
- This shift reduces the concentration of \( OH^- \) ions because they are being consumed to form \( NH_4OH \).

### Step 4: Implications for Precipitation
- The decrease in \( OH^- \) concentration affects the solubility product constant (\( K_{sp} \)) of certain compounds that may precipitate in the presence of hydroxide ions.
- By controlling the concentration of \( NH_4OH \) through the addition of \( NH_4Cl \), we can manage the precipitation of certain metal hydroxides that depend on \( OH^- \) concentration.

### Conclusion
- The addition of solid \( NH_4Cl \) prior to \( NH_4OH \) helps control the concentration of \( NH_4OH \) and \( OH^- \) ions, which is crucial for the analysis of the third component in the mixture.