JEE Chemistry 2023 Question with Solution

Given: Boric acid is solid at room temperature, whereas $BF_3$ is a gas.

Find: The reason for the difference in physical state.

Boric acid has strong hydrogen bonding between its molecules, which increases intermolecular attraction and makes it solid at room temperature. $BF_3$ has covalent bonds but does not show strong hydrogen bonding, so it remains a gas.

Therefore, the correct option is C: Strong hydrogen bond in Boric acid.

The solution shows option A, but the explanation clearly concludes that the correct answer is (3) Strong hydrogen bond in Boric acid. Hence the answer is taken as C from the solution working.

Given: Compare boric acid and $BF_3$ at room temperature.

Find: Which interaction explains why boric acid is solid.

The key distinction is intermolecular force, not merely the presence of covalent bonds. In boric acid, strong hydrogen bonding holds the molecules together in the solid state. In $BF_3$, although the molecule contains covalent bonds internally, it lacks strong intermolecular hydrogen bonding.

So the stronger intermolecular attraction in boric acid is due to hydrogen bonding, which makes it solid at room temperature.