JEE Chemistry 2025 Question with Solution

Given: The compounds are $\text{HBr}$, $\text{H}_2\text{S}$, $\text{NF}_3$, and $\text{CCl}_3$.

Find: The increasing order of their dipole moments.

Principle: Dipole moment depends on both bond polarity and molecular geometry. It is given by

where $\delta$ is the charge separation and $d$ is the distance between charges.

From the solution discussion:

1. $\text{HBr}$ is a polar diatomic molecule with a small dipole moment.
2. $\text{H}_2\text{S}$ has a small dipole moment.
3. $\text{NF}_3$ has a moderate dipole moment because of its pyramidal shape, though lone pair effects partially cancel the bond dipoles.
4. $\text{CCl}_3$ is taken here to have the highest dipole moment among the given compounds.

Therefore, the increasing order is

So, the correct option is C.

Given: We compare molecular dipole moments using bond polarity and shape.

Find: Which sequence arranges the compounds in increasing dipole moment.

The solution states that molecular geometry plays a crucial role because individual bond dipoles may cancel or reinforce each other. Using that comparison:

• $\text{H}_2\text{S}$ is taken as the least among the given compounds.
• $\text{HBr}$ is slightly greater than $\text{H}_2\text{S}$.
• $\text{NF}_3$ has a larger dipole moment due to its trigonal pyramidal geometry.
• $\text{CCl}_3$ is considered the largest in the provided solution.

Hence,

This matches option C. The provided explanation contains some wording inconsistencies about symmetry, but the final conclusion and marked correct option are both C.