JEE Chemistry 2023 Question with Solution

Given: We need to identify which pair consists of polar molecular solids.

Find: The correct option containing two substances that are polar molecules and form molecular solids.

Polar molecular solids are formed by polar molecules held together by dipole-dipole interactions.

• $SO_2$ has a bent structure and a net dipole moment, so it is polar.
• $NH_3$ has a trigonal pyramidal structure and a net dipole moment, so it is polar.
• $CO_2$ is linear and nonpolar.
• $MgO$ is an ionic solid.
• $HCl$ is polar, but $AlN$ is not a polar molecular solid; it is ionic.
• $AlN$ is an ionic solid.

Therefore, the pair $SO_2(s), NH_3(s)$ is an example of polar molecular solids. The correct option is B.

Given: Four pairs of solids are listed.

Find: Which pair contains only polar molecular solids.

Check each option:

1. $SO_2(s), CO_2(s)$: $SO_2$ is polar, but $CO_2$ is nonpolar. Reject.
2. $SO_2(s), NH_3(s)$: both $SO_2$ and $NH_3$ are polar molecules. Accept.
3. $MgO(s), SO_2(s)$: $MgO$ is ionic, so the pair is not a molecular solid pair. Reject.
4. $HCl(s), AlN(s)$: $HCl$ is polar, but $AlN$ is ionic. Reject.

Hence, only option B satisfies the condition.