Halliday, Resnick & Walker — The Kinetic Theory of Gases: Problem 27

Water standing in the open at 32.0°C evaporates because of the escape of some of the surface molecules. The heat of vaporization (539 cal/g) is approximately equal to \(\epsilon n\), where \(\epsilon\) is the average energy of the escaping molecules and \(n\) is the number of molecules per gram. (a) Find \(\epsilon\). (b) What is the ratio of \(\epsilon\) to the average kinetic energy of \(H_2O\) molecules, assuming the latter is related to temperature in the same way as it is for gases?