Question

Hydrogen fluoride is a low boiling liquid, while all other hydrogen halides are gases at room temperature. Comment and explain.

Answer 1

1. Hydrogen fluoride (HF) exists as a liquid at room temperature with a relatively low boiling point (292 K).
2. This is because HF molecules form strong intermolecular hydrogen bonds.
3. Hydrogen bonding occurs due to the small size and high electronegativity of fluorine.
4. These hydrogen bonds cause HF molecules to associate, increasing intermolecular forces and boiling point.
5. Other hydrogen halides (HCl, HBr, HI) do not exhibit hydrogen bonding significantly because their halogen atoms are larger and less electronegative.
6. Due to weaker intermolecular forces (mainly van der Waals forces), other hydrogen halides remain gases at room temperature.

Hence, hydrogen bonding in HF makes it a low-boiling liquid, unlike the gaseous nature of other hydrogen halides.