What quantity of heat energy transfer is required to vaporize 0.500 mL of mercury at 357 °C, its normal boiling point? The density of Hg (l ) is 13.6 g/mL. Compare this heat energy transfer with the amount needed to vaporize 0.500 mL water. See Table 11.2 for the molar enthalpy of vaporization of H2O.