Which of the following is copper (I) compound ?

Options

A. `[Cu(H_(2)O)_(4)]^(2+)`
B. `[Cu(CN)_(4)]^(3-)`
C. `[Cu(NH_(3))_(4)]^(2+)`
D. All of these

Answer

To determine which of the given compounds is a copper (I) compound, we need to analyze the oxidation state of copper in each compound.

### Step-by-Step Solution:

1. **Identify the Compounds**: We have three compounds to analyze:
- Compound 1: \( \text{[Cu(H}_2\text{O)}_4]^{2+} \)
- Compound 2: \( \text{[Cu(CN)}_4]^{3-} \)
- Compound 3: \( \text{[Cu(NH}_3)_4]^{2+} \)

2. **Analyze Compound 1**:
- The oxidation state of copper (Cu) is denoted as \( x \).
- Water (H₂O) is a neutral ligand, contributing 0 to the charge.
- The overall charge on the coordination sphere is +2.
- Therefore, we set up the equation:
\[ x + 0 = +2 \implies x = +2 \]
- Conclusion: Copper in this compound is in the +2 oxidation state.

3. **Analyze Compound 2**:
- Again, let the oxidation state of copper be \( x \).
- Each cyanide ion (CN) has a charge of -1, and there are 4 cyanide ions, contributing -4 to the charge.
- The overall charge on the coordination sphere is -3.
- Set up the equation:
\[ x + (-4) = -3 \implies x - 4 = -3 \implies x = +1 \]
- Conclusion: Copper in this compound is in the +1 oxidation state.

4. **Analyze Compound 3**:
- Let the oxidation state of copper be \( x \).
- Ammonia (NH₃) is also a neutral ligand, contributing 0 to the charge.
- The overall charge on the coordination sphere is +2.
- Set up the equation:
\[ x + 0 = +2 \implies x = +2 \]
- Conclusion: Copper in this compound is in the +2 oxidation state.

5. **Final Conclusion**:
- From the analysis, we find that only Compound 2 (\( \text{[Cu(CN)}_4]^{3-} \)) has copper in the +1 oxidation state. Therefore, the correct answer is:
- **Copper (I) compound is \( \text{[Cu(CN)}_4]^{3-} \)**.