If B-Cl bond has a dipole moment, explain why `BCl_3` molecule has zero dipole moment.

Explanation

The B-atom in `BCl_3` molecule is `sp^2` -hybridised and the molecule posses trigonal planar geometry. As the molecule is symmetrical, the resultant dipole moment of the three B-Cl bonds is zero. Thus `BCl_3` molecule has zero dipole moment.