Which of the following statements is /are true?
I. `Cu^(2+)` salts form soluble complex with excess KCN
II.`Cu^(2+)` salts form soluble complex with aqueous ammonia
III. `Cu^(2+)` salts form soluble complex with KI.
IV. A piece of iron or zinc when placed in `Cu^(2+)` salt solution, precipitates copper.

Options

A. I, III, IV
B. I, II,III
C. I,II,IV
D. None

Answer

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

### Step 1: Analyze Statement I
**Statement I:** `Cu^(2+)` salts form soluble complex with excess KCN.

- When `Cu^(2+)` reacts with KCN, it forms a complex. The reaction is:
\[ \text{Cu}^{2+} + 2 \text{CN}^- \rightarrow \text{Cu(CN)}_2^{2-} \]
- In the presence of excess KCN, the soluble complex formed is:
\[ \text{K}_3\text{Cu(CN)}_4 \]
- Since this complex is soluble, **Statement I is true**.

### Step 2: Analyze Statement II
**Statement II:** `Cu^(2+)` salts form soluble complex with aqueous ammonia.

- When `Cu^(2+)` reacts with aqueous ammonia, it forms a complex:
\[ \text{Cu}^{2+} + 4 \text{NH}_3 \rightarrow \text{Cu(NH}_3)_4^{2+} \]
- This complex is also soluble in water. Therefore, **Statement II is true**.

### Step 3: Analyze Statement III
**Statement III:** `Cu^(2+)` salts form soluble complex with KI.

- When `Cu^(2+)` is mixed with KI, it forms a precipitate:
\[ 2 \text{Cu}^{2+} + 4 \text{I}^- \rightarrow \text{Cu}_2\text{I}_2 \text{ (s)} \]
- The precipitate of copper(I) iodide (CuI) is brown and is not soluble in water. Thus, **Statement III is false**.

### Step 4: Analyze Statement IV
**Statement IV:** A piece of iron or zinc when placed in `Cu^(2+)` salt solution, precipitates copper.

- According to the reactivity series, zinc is more reactive than copper. When zinc is placed in a solution of copper(II) sulfate, the reaction is:
\[ \text{Zn} + \text{CuSO}_4 \rightarrow \text{Cu} + \text{ZnSO}_4 \]
- This shows that zinc displaces copper from the solution, resulting in the precipitation of copper. Therefore, **Statement IV is true**.

### Conclusion
The true statements are:
- Statement I: True
- Statement II: True
- Statement III: False
- Statement IV: True

Thus, the correct answer includes Statements I, II, and IV.

### Final Answer
The true statements are I, II, and IV.

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