why the boiling point of HI is higher than HCl despite HCl b

why the boiling point of HI is higher than HCl despite HCl being more polar than HI.

Solution

HI has the highest boiling point because it has the strongest van der waals attractions.

Larger species have stronger van der waals attractions because they are more polarizable i.e. a fraction of their charge can more easily be localized to a specific spot when it encounters another charge. Iodine is gigantic. An iodine atom is roughly the size of an entire benzene ring, for reference. It is extremely polarizable. Chlorine is not as polarizable.

Hence, here vanderwalls force is more dominant than the dipole-dipole interaction.