If `B-Cl` bond has a dipole moment, explain why `BCl_(3)` molecule has zero dipole moment.

Explanation

`Cl` is more electronegative than `B`, hence due to electronegativity defference between `B` and `Cl`,`B-Cl` bond is polar and has a finite dipole moment. But the dipole moment of the molecule depends on its geometry. `BCl_(3)` is a polar molecular is which the three `B-Cl` bonds are present at an angle of `120^(@)`.Therefore, the resultant of two `B-Cl` bonds is cancelled by equal and opposite dipole moment of `BCl_(3)`. Hence, the overall dipole moment of `BCl_(3)` is zero.