Question

Match the following:

(1)HCl (i) Polar Molecular solid

(2)Ice (ii) Non-polar Molecular solid

(3)CCl${}_4$ (iii) H-bonded Molecular solid

• A. (1)-(i), (2)-(iii), (3)-(ii)
• B. (1)-(ii), (2)-(iii), (3)-(i)
• C. (1)-(iii), (2)-(ii), (3)-(i)
• D. (1)-(i), (2)-(ii), (3)-(iii)

Answer 1

The correct option is A

(1)-(i), (2)-(iii), (3)-(ii)

For this, first we need to know the definitions of polar, non-polar and H-bonded molecular solids.

In some solids, the molecules contain polar covalent bonds between H and F, O, or N atoms.

There is electronegativity difference between H and F,O or N. So there is strong electrostatic force of attraction between Hydrogen from one molecule with O,N or F of another molecule. This is known as hydrogen bond.

Hence, the intermolecular forces of attraction in these molecules are the strong hydrogen bonds.

Polar molecular solids: The intra – molecular forces of attraction are formed by polar covalent bonds. The molecules are held by relatively stronger dipole-dipole interactions.

Dipole-dipole force of attraction

Non-polar molecular solids: They are formed by either atoms (e.g., He and Ar) or molecules formed by non polar covalent bonds (e.g., $H_2$, $C{l}_2$, and $I_2$). The atoms or molecules are held by weak dispersion forces or London forces.

Here in HCl, There is dipole dipole interaction between molecules of HCl. Therefore, it is a polar molecular solid.

You might be wondering why dipole-dipole interaction?

The electronegativity difference is very high between H and Cl. Therefore a partial charge exists in H and Cl which leads to dipole-dipole interaction between these molecules.

Now, if we look at Ice, we know that if there is bonding between H and F, O or N atoms, it leads to hydrogen bonding. This is the case in ice too. There is intermolecular H-bonding between $H_{2}O$ molecules.

In case of $CC{l}_4$, since it is non-polar. These molecules will be held by weak dispersion forces.