Question

In a polar molecule, the ionic charge is$4.8\times {{10}^{-10}}e.s.u.$ If the inter-ionic distance is 1Å unit, then the dipole moment is
(A) $41.8D$
(B) $4.18D$
(C) $4.8D$
(D) $0.48D$

Answer 1

Hint: Dipole moment measures the electronegativity difference between two atoms of a bond. If the two atoms of a bond have differences in their electronegativities, then the bond is said to be polar. Ionic bonds are polar in nature and covalent bonds can be polar if the two atoms attached to the covalent bond have a difference in their electronegativities.

Formula Used: The dipole moment is a product of the magnitude of charge (q) and the distance between two atoms of a bond (d). It is denoted by $\mu $.
$\mu =q\times d$
The units of dipole moment are debye (D) or e.s.u.-cm.

Complete Step by Step Answer:
The given ionic charge = $4.8\times {{10}^{-10}}e.s.u.$
The given inter-ionic distance = 1Å

As the unit of dipole moment is ‘cm’, so we have to convert the inter-ionic distance from angstrom to centimetre.
\[1Å={{10}^{-8}}cm\]
So, the inter-ionic distance is \[{{10}^{-8}}cm\]
Thus, the dipole moment is given by

Dipole moment = ionic charge × inter-ionic distance
$\mu =q\times d$
$\mu =4.8\times {{10}^{-10}}\times {{10}^{-8}}$
\[\mu =(4.8\times {{10}^{-10}})\times {{10}^{-8}}\]
\[\mu =4.8\times {{10}^{-8}}e.s.u.-cm\]
$\mu =4.8D$
Correct Option: (C) $4.8D$.

Note: The dipole moment is a vector quantity that has both magnitude and direction. When a bond is polar, the two atoms of a bond have an unequal sharing of electrons; that is, one atom has a tendency to attract the shared pair of electrons. The dipole moment always occurs from a more electronegative element to a less electronegative element.