Question

How many of the following have zero dipole moment $H_2S, CH_4, NH_3, BF_3, SO_2, NF_3$

Answer 1

Correct Answer: 2

To determine how many of these molecules have zero dipole moment, we must consider each molecule's shape and the distribution of its charges.

• $H_2S$: This molecule is bent, similar to water, due to the V-shaped structure from the lone pairs on sulfur. This results in a net dipole moment. Hence, $H_2S$ does not have zero dipole moment.
• $CH_4$: Methane is tetrahedral with symmetrical charge distribution, leading to a cancellation of dipole moments. Thus, $CH_4$ has zero dipole moment.
• $NH_3$: Ammonia has a trigonal pyramidal shape caused by a lone pair on the nitrogen, resulting in a net dipole moment. Therefore, $NH_3$ does not have zero dipole moment.
• $BF_3$: Boron trifluoride is a planar molecule with trigonal symmetry, resulting in the cancellation of dipole moments. Consequently, $BF_3$ has zero dipole moment.
• $SO_2$: Sulfur dioxide has a bent shape, which leads to a net dipole moment as the dipoles do not cancel out. Therefore, $SO_2$ does not have zero dipole moment.
• $NF_3$: Nitrogen trifluoride is pyramidal due to the lone pair on the nitrogen, giving it a net dipole moment. Thus, $NF_3$ does not have zero dipole moment.

After analyzing each molecule, we find that 2 of them have zero dipole moment: $CH_4$ and $BF_3$. The calculated result, \(2\), fits within the expected range provided, 2 to 2.