Given below are two statements : one is labelled as Assertion (A) and the other is labelled as Reason (R). Assertion (A) : \(\mathrm{NH}_3\) and \(\mathrm{NF}_3\) molecule have pyramidal shape with a lone pair of electrons on nitrogen atom. The resultant dipole moment of \(\mathrm{NH}_3\) is greater than that of \(\mathrm{NF}_3\). Reason (R) : In \(\mathrm{NH}_3\), the orbital dipole due to lone pair is in the same direction as the resultant dipole moment of the \(\mathrm{N}-\mathrm{H}\) bonds. \(\mathrm{F}\) is the most electronegative element. In the light of the above statements, choose the correct answer from the options given below :

• Correct answer
  A

  Both (A) and (R) are true and (R) is the correct explanation of (A)
• B

  (A) is false but (R) is true
• C

  Both (A) and (R) are true but \((\mathbf{R})\) is NOT the correct explanation of (A)
• D

  (A) is true but \((\mathbf{R})\) is false

Solution

Resultant dipole moment $=0.80 \times 10^{-30} \mathrm{Cm}$
Resultant dipole moment $=4.90 \times 10^{-30} \mathrm{~cm}$

Hence, the correct answer is option: 'A'.