Final answer:
The higher boiling point of HBr compared to HCl is due to stronger intermolecular forces, specifically dipole-dipole interactions, which are stronger in HBr. However, HF has an even higher boiling point because of its ability to form strong hydrogen bonds owing to the high electronegativity of fluorine.
Step-by-step explanation:
The normal boiling point for hydrogen bromide (HBr) is higher than that for hydrogen chloride (HCl), which can be explained by the stronger intermolecular forces in HBr. The boiling points of hydrogen halides differ mainly due to variations in the strength of these forces. Hydrogen fluoride (HF), in particular, has an anomalously high boiling point due to its ability to form hydrogen bonds. These bonds are much stronger than the other types of intermolecular forces, like London dispersion forces or dipole-dipole interactions, which are present in other hydrogen halides such as HCl, HBr, and HI. The ability of HF to undergo hydrogen bonding is due to the high electronegativity of fluorine, creating a large dipole that enables these strong interactions. In comparison, while HBr also exhibits dipole-dipole interactions due to the difference in electronegativity between hydrogen and bromine, these forces are less powerful than the hydrogen bonds in HF, yet stronger than in HCl, leading to a higher boiling point than HCl but lower compared to HF.