P PA Lvap k Relative humidity = 17 - 21/) = 50% T mass of air molecules m = 28.8 x 10- kg/mole P PA 1 the heat of evaporation of water Lvap = 40.65 Avogadro number = 6.02 x 1023 mole-1 Boltzmann constant k = 1.38 10-2J K- calculate the temperature at the dew point. k Lvap the ambient temperature T = 27 degree C (= 300 K) In (2), and the following data kJ 40.65103 mole 6.021023 = J/molecule