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(A) Calculate the specific heat capacity at constant volume of water vapor, assuming the nonlinear tri-atomic molecules has three translational and three rotational degree of freedom and that vibrational motion does not contribute. The molar mass of water is 18 g/mol.(B) The actual specific heat capacity of water vapor at low pressure is about 2000 J/kg*K. Compare this with your calculation and comment on the actual role of vibrational motion.he molar mass of water is 18 g/mol. (B) The actual specific heat capacity of water vapor at low pressure is about 2000 J/kg*K. Compare this with your calculation and comment on the actual role of vibrational motion.
Boiling occurs when the vapor pressure reaches or exceeds the surrounding pressure from the atmosphere or whatever else is in contact with the liquid. At standard atmospheric pressure (1 atmosphere = 0.101325 MPa), water boils at approximately 100 degrees Celsius. That is simply another way of saying that the vapor pressure of water at that temperature is 1 atmosphere. At higher pressures (such as the pressure generated in a pressure cooker), the temperature must be higher before the vapor pressure reaches the surrounding pressure, so water under pressure boils at a higher temperature.