In the reaction `BCl_(3) + PH_(3) rarr Cl_(3)B rarr PH_(3)`, Lewis base is

Options

A. `BCl_(3)`
B. `PH_(3)`
C. `Cl_(3)B rarr PH_(3)`
D. None of these

Explanation

To determine the Lewis base in the reaction \( BCl_3 + PH_3 \rightarrow BCl_3 \cdot PH_3 \), we can follow these steps:

### Step 1: Identify the reactants
We have two reactants in this reaction: \( BCl_3 \) (Boron trichloride) and \( PH_3 \) (Phosphine).

### Step 2: Understand the definitions
- A **Lewis acid** is a species that can accept a pair of electrons.
- A **Lewis base** is a species that can donate a pair of electrons.

### Step 3: Analyze the structure of \( BCl_3 \)
Boron trichloride (\( BCl_3 \)) has an incomplete octet and possesses vacant orbitals. This allows it to accept electron pairs, making it a Lewis acid.

### Step 4: Analyze the structure of \( PH_3 \)
Phosphine (\( PH_3 \)) has a lone pair of electrons on the phosphorus atom. This lone pair can be donated to another atom, making it a potential Lewis base.

### Step 5: Determine the interaction
In the reaction, \( PH_3 \) donates its lone pair of electrons to the vacant orbitals of \( BCl_3 \). This forms an adduct \( BCl_3 \cdot PH_3 \).

### Step 6: Conclusion
Since \( PH_3 \) donates the lone pair and \( BCl_3 \) accepts it, we can conclude that:
- **Lewis base**: \( PH_3 \)
- **Lewis acid**: \( BCl_3 \)

Thus, the Lewis base in the reaction is \( PH_3 \).

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