Question

Given the electronegativities of $B=2.0$ and $Cl=3.0$
$I$. It is possible to determine that $B{Cl}_3$ is a polar molecule.
$II$. The electronegativity difference between boron and chlorine creates an uneven sharing of electrons in a $B-Cl$ covalent bond.

• A. Statement $I$ is true, Statement $II$ is true
• B. Statement $I$ is true, Statement $II$ is false
• C. Statement $I$ is false, Statement $II$ is true
• D. Statement $I$ is false, Statement $II$ is false

Answer 1

The correct option is C Statement $I$ is false, Statement $II$ is true

B and Cl have different electronegativities and chlorine (E.N. = 3.00) is more electronegative than B(E.N. = 2.00). As a result $B–Cl$ bond is polar and hence has a finite dipole moment. Now $BC{l}_3$ is a planar molecule in which the three B – Cl bonds are inclined at an angle of ${120}^0$. Therefore, the resultant of two B – Cl bonds in cancelled by equal and opposite dipole moment of the bond $B–Cl$ bond as shown.