Question

Write the significance/applications of dipole moment.

Answer 1

In heteronuclear molecules, polarization arises due to a difference in the electronegativities of the constituents of atoms. As a result, one end of the molecule acquires a positive charge while the other end becomes negative. Hence, a molecule is said to possess a dipole.

The product of the magnitude of the charge and the distance between the centres of positive-negative charges is called the dipole moment $(\mu)$ of the molecule. It is a vector quantity and is represented by an arrow with its tail at the positive centre and head pointing towards a negative centre.
Dipole moment $(\mu)$ = charge $(Q)$ x distance of separation $(r)$
The SI unit of a dipole moment is '$esu$'.
$1 \;esu$ = $3.335 \times 10^{ -30}\; cm$

Dipole moment is the measure of the polarity of a bond. It is used to differentiate between polar and non-polar bonds since all non-polar molecules (e.g. $H_2$, $O_2$) have zero dipole moments. It is also helpful in calculating the percentage ionic character of a molecule.