Question

A certain substance A has a boiling point of 78 degrees celcius and substance B has boiling point of 110 degrees celcius.

Which substance has a higher heat of vaporization?

Answer 1

As the strength of the IMFs in a series of liquids increases, the vapor pressures of the liquids decrease. That's why substance A (TB = 78 °C) has a higher heat of vaporization than that of substance B. Strong IMFs result in high viscosity for a liquid. Substance B (TB = 110 °C) will have a higher viscosity.