Question

Statement $1$: Paradichlorobenzene has higher melting point and solubility than that of ortho and meta forms.

Statement $2$: Para isomer has symmetrical structure and can easily pack closely in crystal structure.

• A. Both Statement $1$ and Statement $2$ are correct and Statement $2$ is correct explanation for Statement $1$.
• B. Both Statement $1$ and Statement $2$ are correct and Statement $2$ is not correct explanation for Statement $1$.
• C. Statement $1$ is correct and statement $2$ is wrong.
• D. Statement $1$ is wrong and statement $2$ is correct.

Answer 1

Answer: (A)

Both Statement $1$ and Statement $2$ are correct and Statement $2$ is correct explanation for Statement $1$.

Generally, the melting point of para isomer is quite higher than that of ortho or meta isomers. This is due to the fact that it has a symmetrical structure and therefore, its molecules can easily pack closely in the crystal lattice. As a result, intermolecular forces of attraction are stronger and therefore, greater energy is required to break its lattice and it melts at a higher temperature.
p-dichlorobenzene has zero dipole moment and thus is more non-polar than o- and m- dichlorobenzene which have dipole moments. So, non-polar p-dichlorobenzene dissolves more readily than o-& m-dichlorobenzene in non-polar (organic) solvents.