Which of the following ions dissolve in excess of aq. `NH_(3)`

Options

A. `Al^(3+)`
B. `Cu^(2+)`
C. `Ag^(+)`
D. `Zn^(2+)`

Answer

To determine which of the given ions dissolve in excess aqueous ammonia, we will analyze each ion and its reaction with ammonia. The ions provided are Al³⁺, Cu²⁺, Ag⁺, and Zn²⁺.

### Step-by-Step Solution:

1. **Analyze Al³⁺ Ion:**
- When Al³⁺ reacts with ammonia (NH₃) and water, it forms aluminum hydroxide (Al(OH)₃).
- The balanced reaction is:
\[ Al^{3+} + 3H_2O + 3NH_3 \rightarrow Al(OH)_3 + 3NH_4^+ \]
- Aluminum hydroxide is insoluble in excess ammonia, meaning no soluble salt is formed.
- **Conclusion:** Al³⁺ does not dissolve in excess aqueous ammonia.

2. **Analyze Cu²⁺ Ion:**
- When Cu²⁺ reacts with ammonia and water, it forms copper(II) hydroxide (Cu(OH)₂).
- The balanced reaction is:
\[ Cu^{2+} + 2H_2O + 2NH_3 \rightarrow Cu(OH)_2 + 2NH_4^+ \]
- Copper(II) hydroxide is insoluble in water, but it dissolves in excess ammonia to form a soluble complex:
\[ Cu(OH)_2 + 4NH_3 \rightarrow [Cu(NH_3)_4]^{2+} + 2OH^- \]
- **Conclusion:** Cu²⁺ dissolves in excess aqueous ammonia.

3. **Analyze Ag⁺ Ion:**
- When Ag⁺ reacts with ammonia and water, it forms silver hydroxide (AgOH).
- The balanced reaction is:
\[ Ag^{+} + H_2O + NH_3 \rightarrow AgOH + NH_4^+ \]
- Silver hydroxide is also insoluble in water, but it dissolves in excess ammonia to form a soluble complex:
\[ AgOH + 2NH_3 \rightarrow [Ag(NH_3)_2]^+ + OH^- \]
- **Conclusion:** Ag⁺ dissolves in excess aqueous ammonia.

4. **Analyze Zn²⁺ Ion:**
- When Zn²⁺ reacts with ammonia, it forms zinc hydroxide (Zn(OH)₂).
- The balanced reaction is:
\[ Zn^{2+} + 2H_2O + 2NH_3 \rightarrow Zn(OH)_2 + 2NH_4^+ \]
- Zinc hydroxide is insoluble in water, but it dissolves in excess ammonia to form a soluble complex:
\[ Zn(OH)_2 + 4NH_3 \rightarrow [Zn(NH_3)_4]^{2+} + 2OH^- \]
- **Conclusion:** Zn²⁺ dissolves in excess aqueous ammonia.

### Final Answer:
The ions that dissolve in excess aqueous ammonia are **Cu²⁺, Ag⁺, and Zn²⁺**.