JEE MAIN - Chemistry (2025 - 22nd January Evening Shift - No. 9)

Arrange the following compounds in increasing order of their dipole moment :

$\mathrm{HBr}, \mathrm{H}_2 \mathrm{~S}, \mathrm{NF}_3$ and $\mathrm{CHCl}_3$
$\mathrm{HBr}<\mathrm{H}_2 \mathrm{~S}<\mathrm{NF}_3<\mathrm{CHCl}_3$
$\mathrm{H}_2 \mathrm{~S}<\mathrm{HBr}<\mathrm{NF}_3<\mathrm{CHCl}_3$
$\mathrm{NF}_3<\mathrm{HBr}<\mathrm{H}_2 \mathrm{~S}<\mathrm{CHCl}_3$
$\mathrm{CHCl}_3<\mathrm{NF}_3<\mathrm{HBr}<\mathrm{H}_2 \mathrm{S}$

Explanation

We need to compare the experimental (or well‐established) dipole moments of the given molecules: $\mathrm{HBr}, \mathrm{H_2S}, \mathrm{NF_3},$ and $\mathrm{CHCl_3}$.


1. $\mathbf{NF_3}$

Structure: Trigonal pyramidal (like $\mathrm{NH_3}$), but each bond is more polar toward fluorine.

Net dipole moment: Quite small, about $0.23\text{–}0.24\,D$ (the bond dipoles partly oppose the lone‐pair contribution).

2. $\mathbf{HBr}$

Structure: Simple diatomic.

Dipole moment: About $0.78\,D$.

3. $\mathbf{H_2S}$

Structure: Bent (like $\mathrm{H_2O}$) but S is less electronegative than O, and the S–H bond angle is wider than the O–H angle in water.

Dipole moment: About $0.95\,D$.

4. $\mathbf{CHCl_3}$ (chloroform)

Structure: Tetrahedral around carbon with three Cl and one H.

Dipole moment: About $1.01\,D$.


Ordering from smallest to largest dipole moment

$ \boxed{\mathrm{NF_3} \;<\; \mathrm{HBr} \;<\; \mathrm{H_2S} \;<\; \mathrm{CHCl_3}.} $

Hence, the correct choice is:

$ \boxed{\text{Option (C)}\quad NF_3 < HBr < H_2S < CHCl_3.} $

Comments (0)

Advertisement