Which of the following options represent the change in the bond
angle in given reaction `:`
`BF_(3)rarrBF_(4)^(-)`

Options

A. `120^(@)`
B. `109^(@)98`
C. `10^(@)72`
D. `60^(@)`

Explanation

To solve the question regarding the change in bond angle during the reaction from BF3 to BF4^(-), we will follow these steps:

### Step 1: Determine the structure and hybridization of BF3
- BF3 (Boron Trifluoride) has a trigonal planar structure due to sp² hybridization.
- Boron has 3 valence electrons and forms three bonds with fluorine atoms.
- The bond angle in BF3 is approximately 120°.

### Step 2: Determine the structure and hybridization of BF4^(-)
- BF4^(-) (Tetrafluoroborate ion) is formed when an additional fluoride ion (F^-) is added to BF3.
- In BF4^(-), boron undergoes sp³ hybridization because it now forms four bonds with fluorine atoms.
- The bond angle in BF4^(-) is approximately 109.5° (or 109° 28').

### Step 3: Calculate the change in bond angle
- The change in bond angle can be calculated by subtracting the bond angle of BF4^(-) from that of BF3.
- Change in bond angle = Bond angle of BF3 - Bond angle of BF4^(-)
- Change in bond angle = 120° - 109.5° = 10.5° (or 10° 72').

### Step 4: Identify the correct option
- Based on the calculated change in bond angle, we can now identify the correct option from the provided choices. The correct answer is the one that matches the calculated change of approximately 10.5°.

### Summary
- The bond angle in BF3 is 120° and in BF4^(-) is approximately 109.5°.
- The change in bond angle when going from BF3 to BF4^(-) is approximately 10.5°.