Question

Water boil at 100oC at a pressure of 1 atm. Calculate the vapour pressure of a water

at 50oC . The heat of vaporization of water is 9.80 Kcal/mol.
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Answer 1

from the thermodynamic point of view, there is an equilibrium between liquid and vapor phase. The vapor pressure is related to temperature (e.g. by Antoine's equations). in MD the driving force is created by the difference in vapor pressures in between two sides of the membrane. Interestingly, you can create the same driving force e.g. 100 hPa using various temperature differences. Please refer to my recent work on driving force in MD, published in Chemical Papers.

NB - even water in the solid state will evaporate - this is a sublimation process.