Question

Which of the following set of molecules will have zero dipole moment?

• A. Ammonia, beryllium difluoride, water, 1,4-dichlorobenzene
• B. Boron trifluoride, hydrogen fluoride, carbon dioxide, 1,3-dichlorobenzene
• C. Nitrogen trifluoride, beryllium difluoride, water, 1,3-dichlorobenzene
• D. Boron trifluoride, beryllium difluoride, carbon dioxide, 1,4-dichlorobenzene

Answer 1

The Correct Option is D

To determine which set of molecules will have a zero dipole moment, it's essential to understand what a dipole moment is and how molecular geometry affects it.

The dipole moment is a measure of the separation of positive and negative charges in a molecule. Molecules with a symmetrical distribution of charge have a zero dipole moment because the individual bond dipoles cancel each other out. Let’s analyze each option provided:

1. Ammonia, beryllium difluoride, water, 1,4-dichlorobenzene:
   • Ammonia (NH₃) has a trigonal pyramidal shape, causing a net dipole moment due to its lone pair.
   • Beryllium difluoride (BeF₂) is linear and thus has a zero dipole moment.
   • Water (H₂O) has a bent shape, resulting in a non-zero dipole moment.
   • 1,4-Dichlorobenzene is symmetrical and thus has a zero dipole moment.
   This set includes molecules with non-zero dipole moments.
2. Boron trifluoride, hydrogen fluoride, carbon dioxide, 1,3-dichlorobenzene:
   • Boron trifluoride (BF₃) has a symmetrical trigonal planar shape, leading to a zero dipole moment.
   • Hydrogen fluoride (HF) is a polar molecule with a non-zero dipole moment.
   • Carbon dioxide (CO₂) is linear and symmetrical, resulting in a zero dipole moment.
   • 1,3-Dichlorobenzene is not symmetrical, so it has a non-zero dipole moment.
   Some molecules have non-zero dipole moments.
3. Nitrogen trifluoride, beryllium difluoride, water, 1,3-dichlorobenzene:
   • Nitrogen trifluoride (NF₃) has a trigonal pyramidal shape, causing a non-zero dipole moment.
   • Water (H₂O) has a bent shape and thus a non-zero dipole moment.
   • 1,3-Dichlorobenzene is not symmetrical, so it has a non-zero dipole moment.
   • Beryllium difluoride (BeF₂) is linear and has a zero dipole moment.
   Many molecules in this set have non-zero dipole moments.
4. Boron trifluoride, beryllium difluoride, carbon dioxide, 1,4-dichlorobenzene:
   • Boron trifluoride (BF₃) has a symmetrical shape (trigonal planar), leading to a zero dipole moment.
   • Beryllium difluoride (BeF₂) is linear and symmetrical, hence has a zero dipole moment.
   • Carbon dioxide (CO₂) is also linear and has a zero dipole moment.
   • 1,4-Dichlorobenzene is symmetrical, so it has a zero dipole moment.
   All molecules in this set have zero dipole moments.

Hence, the correct answer is: Boron trifluoride, beryllium difluoride, carbon dioxide, 1,4-dichlorobenzene, as all the molecules in this set have symmetrical shapes that lead to zero dipole moments.