Write the significance/applications of dipole moment

cbse
chemicalbonding

#1

Applications of Dipole moment:
(1) In determining the polarity of bonds : As $\mu $=e x d, obviously greater is the magnitude of dipole moment, higher will be the polarity of the bond. This is applicable to molecules containing only one polar bond like HCl, HBr etc. In non-polar molecules like ${{H}{2}}$,${{O}{2}}$,${{N}{2}}$,the dipole moment is zero. It is because there is no charge separations in these molecules [e = 0]. Thus dipole moment can also be used to distinguish between polar non-polar molecules.
(2) In the calculation of percentage ionic character.
Take the example of HCl Its $\mu $ = 1.03 D
If HCl is 100% ionic, each end would carry charge = one unit i.e. 4.8 x ${{10}^{-10}}$ e.s.u.
d (bond lenghth) in H - Cl = 1.275 $A\overset{0}{\mathop{{}}},$
for 100% ionic character, dipole moment will be
${{\mu }
{ionic}}$ =e X d
= 48 x ${{10}^{-10}}$ e.s.u. x 1.275 x ${{10}^{-8}}$ cm = 6.12 x ${{10}^{-18}}$ e.s.u. cm = 6.12 D
-----> % ionic characte= ${{\mu }{observed}}$/${{\mu }{ionic}}$x100=1.03/6.12x100=16.83
(3) In determining the symmetry (or shape) of the molecules :
Dipole moment is an important property in determining the shape of molecules containing 3 or more atoms. For instant if any molecule possesses two or more polar bonds, it will not be symmetric if it possesses some net molecular dipole moment as in case of water $\mu $ = 1.84 D and ammonia But if a molecule contains a number of similar atoms linked to a central atom the overall dipole moment of the molecule is found out to be zero.