Which of the following statement(s) is/are with true ?

Options

A. `Cu^(2+)` salt form soluble complex with excess `KCN`
B. `Cu^(2+)` salt form soluble complex with aqueous ammonia
C. `Cu^(2+)` salt form soluble complex with `KI`
D. A pieces of iron or zine when placed in `Cu^(2+)` salt solution , precipitate copper

Explanation

To determine which of the given statements about copper(II) salts are true, we will analyze each statement step by step.

### Step-by-Step Solution:

1. **Analyzing Statement 1:**
- **Statement:** Copper(II) salt forms a soluble complex with excess KCN.
- **Analysis:** When copper(II) ions (Cu²⁺) react with potassium cyanide (KCN), they form cupric cyanide (Cu₂CN₂). When excess KCN is added, this further reacts to form a soluble complex, K₃Cu(CN)₄.
- **Conclusion:** This statement is **true**.

2. **Analyzing Statement 2:**
- **Statement:** Copper(II) salt forms a soluble complex with aqueous ammonia.
- **Analysis:** Aqueous ammonia (NH₃) acts as a ligand and forms a square planar complex with copper(II) ions, specifically [Cu(NH₃)₄]²⁺. This complex is soluble in water.
- **Conclusion:** This statement is **true**.

3. **Analyzing Statement 3:**
- **Statement:** Copper(II) salt forms a soluble complex with KI.
- **Analysis:** Copper(II) ions can react with potassium iodide (KI) to form Cu₂I₂, which is a brown precipitate. This compound is not soluble in water.
- **Conclusion:** This statement is **false**.

4. **Analyzing Statement 4:**
- **Statement:** A piece of iron or zinc placed in a copper(II) salt solution will precipitate copper.
- **Analysis:** Zinc is more reactive than copper and can displace copper from copper(II) sulfate solution. This results in the formation of zinc sulfate and precipitated copper.
- **Conclusion:** This statement is **true**.

### Final Conclusion:
The true statements are:
- Statement 1: True
- Statement 2: True
- Statement 3: False
- Statement 4: True

Thus, the correct options are **1, 2, and 4**.

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