Question

A molecule possessing dipole moment is:

• A. $C{H}_4$
• B. $H_{2}O$
• C. $B{F}_3$
• D. $C{O}_2$

Answer 1

The correct option is B $H_{2}O$

a) Dipole moment of $C{H}_4$ is zero. $C{H}_4$ is tetrahedral in shape and symmetrical. Hence, the resultant dipole moment vectors cancel out and is zero.


b) In a water molecule, the electrons are more localized around the $O$ atom since it is much more electronegative than the $H$ atom. $H_{2}O$ has a bent shape and the lone pairs of electrons have dipole moment vectors upward. Therefore, the individual bond dipole moments do not cancel each other out and the resultant $\mu$ is in the upward direction as shown.



c) Boron trifluoride has zero dipole moment although it has three polar $B—F$ bonds. This is because, $B{F}_3$ has $s{p}^2$ hybridisation and trigonal planal geometry. And hence, the resultant dipole moment vectors get cancelled and the overall dipole moment is zero.

d) Due to the linear shape of $C{O}_2$, the dipole moment gets cancelled. Hence, its dipole moment is zero.