$(a)$ Discuss the significance/applications of dipole moment.
$(b)$ Represent diagrammatically the bond moments and the resultant dipole moment in $CO_2, NF_3$ and $CHCl_3$.

(N/A) The applications of dipole moment are:
$(i)$ The dipole moment helps to predict whether a molecule is polar or non-polar. As $\mu = q \times d$,greater is the magnitude of dipole moment,higher will be the polarity of the bond. For nonpolar molecules,the dipole moment is zero.
$(ii)$ The percentage of ionic character can be calculated as: $\text{Percentage of ionic character} = \frac{\mu_{\text{observed}}}{\mu_{\text{ionic}}} \times 100$.
$(iii)$ Symmetrical molecules have zero dipole moment although they have two or more polar bonds (in determination of symmetry).
$(iv)$ It helps to distinguish between $cis$ and $trans$ isomers. Usually $cis$-isomer has higher dipole moment than $trans$ isomer.
$(v)$ It helps to distinguish between $ortho$,$meta$ and $para$ isomers. Dipole moment of $para$ isomer is zero. Dipole moment of $ortho$ isomer is greater than that of $meta$ isomer.
$(b)$ The diagrammatic representation is as follows:
$O=C=O$ $(m=0)$
$NF_3$ $(m=0.24 \ D)$
$CHCl_3$ $(m=1.03 \ D)$