Question

(i) Discuss the significance/applications of dipole moment.
(ii) Represent diagrammatically the bond moments and the resultant dipole moment in C02, NF3
and CHCl3.

Answer 1

(i) Dipole moment plays very important role in understanding the nature of chemical bond. A
few applications are given below:
(a) Distinction between, polar and non-polar molecules. The measurement of dipole moment can
help us to distinguish between polar and non-polar molecules. Non-polar molecules have zero dipole
moment while polar molecules have some value of dipole moment.
(b) Degree of polarity in a molecule. Dipole moment measurement also gives an idea about the
degree of polarity specially in a diatomic molecule. The greater the dipole moment, the greater is
the polarity in such a molecule.
(c) Shape of molecules. In case of molecules containing more than two atoms, the dipole moment
not only depends upon the individual dipole moments of the bonds but also on the arrangement of
bonds.
.Thus, dipole moment is used to find the shapes of molecules.
(d) Ionic character in a molecule. Knowing the electronegativities of atoms involved in a molecule, it
is possible to predict the nature of chemical bond formed. If the difference in electronegativities of
two atoms is large, the bond will be highly polar. As an extreme case, when the electron is
completely transferred from one atom to another, an ionic bond is formed. Therefore, the ionic
bond is regarded as an extreme case of covalent bond. The greater the difference in
electronegativities of the bonded atoms, the higher is the ionic character
(e) Distinguish between cis- and trans- isomers. Dipole moment measurements help to distinguish
between cis- and trans- isomers because ds-isomer has usually higher dipole moment than trans
isomer.
(f) Distinguish between ortho, meta and para isomers. Dipole moment measurements help to
distinguish between o-, m- and p-isomers because the dipole moment of p-isomer is zero and that of
o-isomers is more than that of m-isomer.