Question

Explain why hydrogen fluoride (HF) has a higher boiling temperature than hydrogen chloride (HCL) (19.4 degree C), even though HF has a lower molecular weight. a. The intermolecular bonding for HF is van der Waals, whereas for HCl, the intermolecular bonding is hydrogen. Since the van der Waals bond stronger than hydrogen, HF will have a higher boiling temperature. b. The intermolecular bonding for HF is covalent, whereas for HCl, the intermolecular bonding is van der Waals. Since the covalent bond is stronger than van der Waals, HF will have higher boiling temperature c. The intermolecular bonding for HF is hydrogen, whereas for HCl, the intermolecular bonding is van der Waals. Since the hydrogen bond is stronger than van der Waals, HF will have higher boiling temperature. d. The atomic number for Cl is greater than for F, so HF will have a higher boiling temperature. e. The atomic weight for Cl is greater than for F, so HF will have a higher boiling temperature.

Answer 1

Answer: c) The intermolecular bonding for HF is hydrogen, whereas for HCl, the intermolecular bonding is van der Waals. Since the hydrogen bond is stronger than van der Waals, HF will have higher boiling temperature.

Explanation:

Due to the high electronegativity of flourine, hydrogen bonds can be formed between HF molecules. Hydrogen bonds require more energy to break. The other halogens are not as electronegative and so other hydrogen halides cannot form hydrogen bonds between molecules. Only London Forces are formed.

Therefore more energy is required to break the intermolecular forces in HF than the other hydrogen halides and so it has a higher boiling point.