Question

Which out of NH3 and NF3 has higher dipole moment and why​

Answer 1

Here you go:

In each molecule, N atom has one lone pair.

F is more electronegative than H and N−F bond is more polar than N−H bond.

Hence, NF₃ is expected to have much larger dipole moment than NH₃

Answer 2

The dipole moment of ammonia (1.47D) is higher than the dipole moment of NF3 (0.24D). the molecular geometry is pyramidal for both the molecules. In each molecule, N atom has one lone pair. F is more electronegative than H and N-F bond is more Polar than N-H bond. Hence, NF3 is expected to have much larger dipole moment than NH3. However reverse is true as in case of ammonia, the direction of the lone pair dipole moment and the bond pair dipole moment is same whereas in case of NF3 it is opposite. Thus, in ammonia molecules, individual dipole moment vectors add whereas in NF3, they cancel each other.