Consider the coordination compound , `[Co(NH_(3))_(6)]Cl_(3)`. In the formation of the complex, the species which acts as the Lewis acid is :

Options

A. `[Co(NH_(3))_(6)]^(3+)`
B. `Cl^(-)`
C. `Co^(3+)`
D. `NH_(3)`

Answer

To determine which species acts as the Lewis acid in the coordination compound `[Co(NH₃)₆]Cl₃`, we will analyze the components of the compound step by step.

### Step-by-Step Solution:

1. **Understanding Lewis Acids and Bases**:
- A Lewis acid is defined as a species that can accept an electron pair.
- A Lewis base is defined as a species that can donate an electron pair.

2. **Identifying the Components of the Coordination Compound**:
- The coordination compound `[Co(NH₃)₆]Cl₃` consists of a central metal ion (cobalt) surrounded by six ammonia (NH₃) ligands and three chloride ions (Cl⁻).

3. **Analyzing the Coordination Compound**:
- The entire coordination compound cannot act as a Lewis acid. It is the central metal ion that plays a crucial role in this context.
- The ligands (NH₃) are neutral molecules that can donate their lone pair of electrons to the central metal ion.

4. **Identifying the Central Metal Ion**:
- In this compound, cobalt is in the +3 oxidation state, denoted as Co³⁺. This positive charge indicates that cobalt has a deficiency of electrons.

5. **Determining the Role of Cobalt**:
- Since Co³⁺ has a positive charge, it can accept electron pairs from the ligands (NH₃). Therefore, cobalt acts as a Lewis acid.

6. **Analyzing the Other Species**:
- The chloride ion (Cl⁻) has a negative charge, which means it has extra electrons and can donate them. Thus, Cl⁻ acts as a Lewis base.
- Ammonia (NH₃) has a lone pair of electrons on nitrogen, which it can donate, making it a Lewis base as well.

7. **Conclusion**:
- The species that acts as the Lewis acid in the formation of the complex `[Co(NH₃)₆]Cl₃` is the cobalt ion in the +3 oxidation state (Co³⁺).

### Final Answer:
The species which acts as the Lewis acid is **Cobalt in the +3 state (Co³⁺)**.

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