Question

Arrange the following compounds in increasing order of their dipole moment:
HBr, H\(_2\)S, NF\(_3\), and CCl\(_3\)

• A. CCl\(_3\) < NF\(_3\) < HBr < H\(_2\)S
• B. NF\(_3\) < HBr < H\(_2\)S < CCl\(_3\)
• C. H\(_2\)S < HBr < NF\(_3\) < CCl\(_3\)
• D. HBr < H\(_2\)S < NF\(_3\) < CCl\(_3\)

Hint:

When comparing dipole moments, remember that molecular geometry plays a crucial role in determining whether individual bond dipoles cancel each other out or contribute to the overall dipole moment.

Answer 1

The Correct Option is C

To rank the compounds HBr, H₂S, NF₃, and CCl₃ by increasing dipole moment, an understanding of dipole moments is required.

Dipole Moment Definition: A dipole moment (μ) quantifies the separation of opposing electrical charges. It is a vector quantity with both magnitude and direction. The formula is:

\[\mu = \delta \times d\]

Here, \( \delta \) represents the charge and \( d \) is the distance between the charges. Molecular dipole moments arise from differences in electronegativity between bonded atoms and the molecule's three-dimensional structure. The standard unit for dipole moment is the Debye (D).

Analysis of each compound:

1. HBr:

Hydrogen bromide is a diatomic molecule. Bromine's higher electronegativity than hydrogen creates a dipole moment, which is relatively small for a simple diatomic molecule.

1. H₂S:

The bent molecular geometry, similar to water, and a slight electronegativity difference between hydrogen and sulfur result in a small dipole moment.

1. NF₃:

Nitrogen trifluoride exhibits a dipole moment due to electronegativity disparities and its pyramidal structure. However, the lone pair of electrons on the nitrogen atom partially counteracts the overall dipole moment.

1. CCl₃:

While CCl₃ might be considered nearly nonpolar due to its symmetry, in this context, the electronegative chlorine atoms induce polarization, leading to a significant dipole moment exceeding that of the other compounds.

The order of increasing dipole moment is as follows:

1. H₂S - exhibits the least dipole moment due to its symmetrical structure and a smaller electronegativity difference.
2. HBr - shows a slight increase in dipole moment compared to H₂S.
3. NF₃ - possesses a moderate dipole moment owing to its pyramidal geometry.
4. CCl₃ - has the largest dipole moment among the given compounds, attributed to the polarity of the C-Cl bonds.

Therefore, the increasing order of dipole moment is: H₂S < HBr < NF₃ < CCl₃.