Question

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

Answer 1

Comparison of dipole moments of NH₃ and NF₃:

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Between NH₃ and NF₃, NH₃ has a higher dipole moment.

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Explanation:

Both NH₃ and NF₃ have a trigonal pyramidal geometry due to the presence of a lone pair on the nitrogen atom.

In NH₃:
• The N–H bond dipoles are directed towards nitrogen because nitrogen is more electronegative than hydrogen.
• The bond dipoles and the lone pair dipole act in the same direction.
• As a result, the dipole moments add up, giving a higher net dipole moment.

In NF₃:
• The N–F bond dipoles are directed away from nitrogen because fluorine is more electronegative than nitrogen.
• The bond dipoles are opposite in direction to the lone pair dipole.
• This leads to partial cancellation of dipole moments, resulting in a lower net dipole moment.

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Conclusion:

NH₃ has a higher dipole moment than NF₃ because in NH₃ the bond dipoles and lone pair dipole reinforce each other, whereas in NF₃ they partially cancel.