Question

Which of the following has a dipole moment as zero?
A.$C{H_2}C{l_2}$
B.$B{F_3}$
C.$N{F_3}$
D.$Cl{O_2}$

Answer 1

Hint:The compounds which have regular geometry and have the same type of atoms. Then, the dipole moment of that compound is zero. The dipole is the vector quantity whose direction is parallel to the bond axis.

Complete step by step answer:
The dipole moment can be defined as the moment which arises when there is a separation of charge in the system. This can exist in ionic bonds and covalent bonds both. This occurs due to the difference in electronegativity between two chemically bonded atoms.
The dipole moment can be calculated by multiplying the magnitude of charge and distance between the centres of the positive and negative charges. It is denoted by $\mu $. We can represent mathematically by –
$\mu = Q \times r$
where, $Q$ is the magnitude of charge and $r$ is the distance of separation.
The S.I unit is Debye which is denoted by $D$.
$1D = 3.336 \times {10^{ - 30}}C.m$
The value of the dipole moment of a compound is zero, if they have regular geometry and have the same type of atoms. Therefore, according to the question –
The dipole moment of $B{F_3}$ is zero because it has triangular planar structure, so it is symmetrical. In the structure of $B{F_3}$, the boron is at centre which is surrounded by the fluorine atoms which lie at the corners of an equilateral triangle.
When the dipole moment of the three bonds are vectorially added they give the net sum as zero because the resultant of any two dipole moments is equal and opposite to the third. The structure of $N{F_3}$ is unsymmetrical so, the dipole moment cannot be zero and the molecule $C{H_2}C{l_2}$ is also unsymmetrical so, its dipole moment cannot be zero.
Therefore, $B{F_3}$ has dipole moment equal to zero.

Hence, the correct option is (B).

Note:The application of dipole moment is to find out the difference between polar and non – polar molecules. It can be used for the determination of the ionic character of a molecule and can also be used for deciding the geometry of a molecule.