Which of the following molecules have the lowest boiling point?
HF
HBr
HCl
HI
Vander Waal forces of attraction and molecular weights determine the boiling points. The Vander Waal force is stronger for molecules with higher molecular masses and also for molecules having greater polarity. These two factors are sometimes opposing in nature and the boiling points of species are often factual.
Among the given species, the order of boiling points follow the order
HF > HI > HBr > HCl
Option (c) is correct