To determine which of the following precipitates is soluble in excess ammonia (NH₃) solution, we need to analyze the behavior of different metal ions when they react with excess ammonia. Here are the steps to solve the problem:
### Step 1: Identify the Metal Ions
List the metal ions provided in the question. For this solution, we will consider the following ions:
- Zn²⁺
- Cd²⁺
- Hg²⁺
- Ag⁺
- Pb²⁺
- Ni²⁺
- Cu²⁺
### Step 2: Analyze Each Metal Ion's Reaction with Excess NH₃
- **Zn²⁺**: When Zn²⁺ reacts with excess NH₃, it forms a soluble complex, [Zn(NH₃)₄]²⁺, which is colorless.
- **Cd²⁺**: Similarly, Cd²⁺ also forms a soluble complex with excess NH₃, which is [Cd(NH₃)₄]²⁺, and is colorless.
- **Hg²⁺**: Hg²⁺ does not form a soluble complex with excess NH₃; instead, it forms an insoluble precipitate.
- **Ag⁺**: Ag⁺ reacts with excess NH₃ to form a soluble complex, [Ag(NH₃)₂]⁺, which is colorless.
- **Pb²⁺**: Pb²⁺ does not form a soluble complex with excess NH₃; it leads to the formation of an insoluble precipitate.
- **Ni²⁺**: Ni²⁺ reacts with excess NH₃ to form a soluble complex, [Ni(NH₃)₄]²⁺, which is colorless.
- **Cu²⁺**: Cu²⁺ also forms a soluble complex with excess NH₃, which is [Cu(NH₃)₄]²⁺, and is colorless.
### Step 3: Summarize the Results
From the analysis:
- Soluble in excess NH₃: Zn²⁺, Cd²⁺, Ag⁺, Ni²⁺, Cu²⁺
- Not soluble in excess NH₃: Hg²⁺, Pb²⁺
### Step 4: Identify the Correct Answer
The question asks for the precipitates that are soluble in excess NH₃. The metal ions that form soluble complexes in excess NH₃ are:
1. Zn²⁺
2. Cd²⁺
3. Ag⁺
4. Ni²⁺
5. Cu²⁺
### Conclusion
The correct answer is that the precipitates formed by Zn²⁺ and Cd²⁺ are soluble in excess ammonia.
