Question

Which among the following is NOT a polar molecular solid?

• A. \(\mathrm{CH_4}\)
• B. \(\mathrm{SO_2}\)
• C. \(\mathrm{HCl}\)
• D. \(\mathrm{H_2S}\)

Hint:

Symmetrical molecules usually have zero dipole moment and form non-polar molecular solids.

Answer 1

The Correct Option is A

Step 1: Understand polar molecular solids.
Polar molecular solids are composed of polar molecules held together by dipole–dipole interactions. These molecules have a permanent dipole moment.

Step 2: Analyse methane (\(\mathrm{CH_4}\)).
Methane is a symmetrical tetrahedral molecule. Although the C–H bonds are slightly polar, their dipole moments cancel out due to symmetry. Hence, methane is a non-polar molecule.

Step 3: Analyse other options.
(B) \(\mathrm{SO_2}\): Bent molecule with a net dipole moment → polar.
(C) \(\mathrm{HCl}\): Polar covalent molecule → polar.
(D) \(\mathrm{H_2S}\): Bent shape with net dipole moment → polar.

Step 4: Conclusion.
Methane does not form a polar molecular solid.