Question

Which of the following conversions involves change in both shape and hybridisation?

• A. $NH _{3} \rightarrow NH _{4}^{+}$
• B. $CH _{4} \rightarrow C _{2} H _{6}$
• C. $H _{2} O \rightarrow H _{3} O ^{+}$
• D. $BF _{3} \rightarrow BF _{4}^{-}$

Answer 1

Answer: (D)

$BF _{3} \rightarrow BF _{4}^{-}$

Answer 2

$BF _{3}$ combines with $F ^{-}$ ion to form $BF _{4}^{-}$.

The shape of the $BF _{3}$ molecule is a planar triangle with bond angles of $120^{\circ}$ and $s p^{2}$ hybridisation.
The shape of the $BF _{4}^{-1}$ molecule is a tetrahedral with bond angles of $108^{\circ}$ and $s p^{3}$ hybridisation.

So, the correct option is (D): $BF _{3} \rightarrow BF _{4}^{-}$