# How many of the following molecules possess dipole moments : BH_3, CH_4, PCl_5, H_20, HF, H_2?

Sep 9, 2017

Only ${H}_{2}$ and $P C {l}_{5}$ possess no dipole moments....
The molecular dipole moment, is the VECTOR sum of the individual bond dipoles. For trigonal planar $B {H}_{3}$ (an hypothetical species), and $C {H}_{4}$, and $P C {l}_{5}$ the individual bond dipoles sum to ZERO. And of course there is no polarity to be considered in the the dihydrogen molecule....
For ${H}_{2} O$ and $H - F$ there is bond polarity, i.e. ""^(delta+)H-stackrel(delta-)O-H^(delta+), and ""^(delta+)H-F^(delta-), and because the individual bond dipoles do not SUM to ZERO...both the acid and the water are polar molecules.
$\text{Chloroform}$, $C H C {l}_{3}$, has some polarity, however, $\text{carbon tetrachloride}$ is a non-polar molecule given that the ""^(delta+)C-Cl^(delta-) dipoles sum to zero given a tetrahedral geometry.