Question

The variation of the boiling points of the hydrogen halides is in the order HF > HI > HBr > HCl.

What explains the higher boiling point of hydrogen fluoride?

(a) There is strong hydrogen bonding between HF molecules.

(b) The bond energy of HF molecules is greater than in other hydrogen halides.

(c) The effect of nuclear shielding is much reduced in fluorine which polarises the HF molecule.

(d) The electronegativity of fluorine is much higher than for other elements in the group.

Answer 1

Correct option (a) There is strong hydrogen bonding between HF molecules.

Explanation :

HF forms strong intermolecular H-bonding due to high electronegativity of F. Hence, the boiling point of HF is abnormally high. Boiling points of other hydrogen halides graduaily increase from HCl to HI due to increase in size of halogen atoms from Cl to I which further increase the magnitude of van der Waals forces.