JEE Main 2024 — 5 April, Shift 2 — Question 64

Assertion (A) is True: Both $\mathrm{NH_3}$ and $\mathrm{NF_3}$ are trigonal pyramidal molecules with alone pair of electrons on the nitrogen atom. The resultant dipole moment of $\mathrm{NH_3}$ is greater than that of $\mathrm{NF_3}$.

Reason (R) is True and correct explanation: In $\mathrm{NH_3}$, the dipole moment due to the lone pair is in the same direction as the resultant dipole moment of the $N-H$ bonds, leading to a larger net dipole moment. In $\mathrm{NF_3}$, because fluorine is highlyelectronegative, the $N-F$ bond dipoles oppose the lone-pair dipole, resulting in a smaller net dipole moment.

Therefore, both (A) and (R) are true and (R) is the correct explanation of (A).

 Resultant dipole moment $=0.80\times {{10}^{-30}}\text{Cm}$

 Resultant dipole moment $=4.90\times {{10}^{-30}}\text{Cm}$