Question

Boiling point of HCl is -85⁰C and boiling point of HF is 85. How can you accounts this big difference (~100⁰C) in boiling points between these two similar acids?

Answer 1

Answer:

The big difference in boiling point between HF and HCl is due to greater intermolecular hydrogen bonding in HF.

Explanation:

Intermolecular Hydrogen bonding is possible in any molecule that has a hydrogen atom directly connected to an electronegative atom. Molecules with an electronegative atom attached to a hydrogen atom will have a higher boiling point compared to molecules of similar sizes.

Here F is more electronegative than Cl. So HF can form extensive intermolecular hydrogen bonding compared to HCl which is less polarized. Thus HF will have a greater boiling point compared to HCl.