Which of the following compound will not turn black on adding `NH_(4)OH` to it ?

Options

A. `ZnSO_(4)`
B. `Hg_(2)Cl_(2)`
C. `AgCl`
D. `CuSO_(4)`

Answer

To solve the question of which compound will not turn black on adding `NH₄OH`, we need to analyze the reactions of each compound with ammonium hydroxide (NH₄OH) and observe the products formed.

### Step-by-Step Solution:

1. **Identify the Compounds**: The compounds given in the question are:
- Zinc sulfate (ZnSO₄)
- Mercury(I) chloride (Hg₂Cl₂)
- Silver chloride (AgCl)
- Copper sulfate (CuSO₄)

2. **Reaction of Zinc Sulfate with NH₄OH**:
- The reaction is:
\[ \text{ZnSO}_4 + \text{NH}_4\text{OH} \rightarrow \text{Zn(OH)}_2 \downarrow + \text{(NH}_4)_2\text{SO}_4 \]
- Zinc hydroxide (Zn(OH)₂) forms a white precipitate and does not turn black.

3. **Reaction of Mercury(I) Chloride with NH₄OH**:
- The reaction is:
\[ \text{Hg}_2\text{Cl}_2 + \text{NH}_4\text{OH} \rightarrow \text{HgNH}_2 + \text{Hg} + \text{NH}_4\text{Cl} + 2\text{H}_2\text{O} \]
- This reaction produces mercury (Hg), which is black in color, indicating that this compound will turn black.

4. **Reaction of Silver Chloride with NH₄OH**:
- The reaction is:
\[ \text{AgCl} + 2\text{NH}_4\text{OH} \rightarrow \text{Ag(NH}_3)_2\text{Cl} + 2\text{H}_2\text{O} \]
- This reaction produces a complex ion (Ag(NH₃)₂Cl) and does not produce a black precipitate, remaining white.

5. **Reaction of Copper Sulfate with NH₄OH**:
- The reaction is:
\[ \text{CuSO}_4 + 4\text{NH}_4\text{OH} \rightarrow \text{Cu(NH}_3)_4\text{SO}_4 + 4\text{H}_2\text{O} \]
- This reaction leads to the formation of a deep blue solution, indicating that it does not turn black.

### Conclusion:
The compounds that do not turn black upon the addition of `NH₄OH` are:
- Zinc sulfate (ZnSO₄)
- Silver chloride (AgCl)
- Copper sulfate (CuSO₄)

Thus, the answer to the question is **Zinc sulfate (ZnSO₄)**, **Silver chloride (AgCl)**, and **Copper sulfate (CuSO₄)**.