Question

why HF (hydrogen fluoride) has higher boiling temperature than HCl (hydrogen chloride), even thought HF has lower molecular weight?

Answer 1

Answer:

Boiling point of HF is higher as compared to HCl because of presence of hydrogen bonding in it.

Explanation:

In HF, intermolecular force of attraction is hydrogen bonding.

Hydrogen bonding is a type of electrostatic force of attraction existing between H atom and electronegative atom.

For a molecule to have hydrogen bonding, H atom must be bonded to electronegative atom, O, N and F.

Hydrogen bonding can be intermolecular and intramolecular.

So, in HF hydrogen bonding present.

In HCl, only van der Waals force exists. van der Waals forces are weak as compared to hydrogen bonding.

Because of presence of hydrogen bonding, HF molecules are held tightly and so requires more heat to boil.

Therefore, boiling point of HF is more as compared to HCl.