In `Cr(CO)_(6)`, how many CO ligands can be replaced by NO?

Options

A. 3
B. 5
C. 6
D. 4

Answer

To solve the question of how many CO ligands in Cr(CO)₆ can be replaced by NO, we can follow these steps:

### Step-by-Step Solution:

1. **Identify the Electron Donating Capacity of CO and NO**:
- Each CO ligand donates 2 electrons.
- Each NO ligand donates 3 electrons.

2. **Calculate the Total Electron Donation from CO Ligands**:
- In Cr(CO)₆, there are 6 CO ligands.
- Total electrons donated by CO ligands = Number of CO ligands × Electrons donated by each CO
- Total electrons = 6 × 2 = 12 electrons.

3. **Set Up the Equation for NO Ligands**:
- Let \( X \) be the number of NO ligands that will replace the CO ligands.
- The total electrons donated by \( X \) NO ligands = Number of NO ligands × Electrons donated by each NO
- Total electrons = \( X \times 3 \).

4. **Equate the Total Electron Donation**:
- Since the total electron donation must remain the same when replacing CO with NO, we set up the equation:
\[ X \times 3 = 12 \]

5. **Solve for \( X \)**:
- To find \( X \), divide both sides of the equation by 3:
\[ X = \frac{12}{3} = 4 \]

6. **Conclusion**:
- Therefore, 4 CO ligands can be replaced by 4 NO ligands in Cr(CO)₆.

### Final Answer:
4 CO ligands can be replaced by NO in Cr(CO)₆.