Question

The dipole moments of the given species are such that

• A. $B{F}_3>N{F}_3>N{H}_3$
• B. $N{F}_3>B{F}_3>N{H}_3$
• C. $N{H}_3>N{F}_3>B{F}_3$
• D. $N{H}_3>B{F}_3>N{F}_3$

Answer 1

Answer: (C)

The dipole moments of the given species are as follows

$N{H}_3>N{F}_3>B{F}_3$

$B{F}_3$ is a planar molecule, so it has zero dipole moment. $N{H}_3$ has more dipole moment than $N{F}_3$ . The resultant dipole moment of three $N-H$ bonds and dipole moment due to lone pair of electrons are acting in the same direction, but in case of $N{F}_3$ the resultant dipole moment of the three $N-F$ bonds is acting opposite to the direction of dipole moment due to lone pair of electrons.