JEE Advanced levelSingle correct optionDifficulty 3 of 3cb153
Assertion (A): NFX3 has a smaller dipole moment than NHX3 although fluorine is more electronegative than hydrogen. Reason (R): In NFX3 the resultant of the N-F bond dipoles opposes the dipole due to the lone pair on nitrogen.
ABoth A and R are true and R is the correct explanation of A
BBoth A and R are true but R is not the correct explanation of A
CA is true but R is false
DA is false but R is true
Answer: A
In NHX3, the N-H bond dipoles (towards N) and the lone pair dipole point the same way and add. In NFX3 the N-F dipoles point towards F, opposing the lone pair dipole, so the net moment is small. Both statements are true and R explains A.