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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.
How does water pressure change with increasing temperature? With air inside, assuming for simplicity constant volume and ideal gas, its pressure variation from 50F to 212F can be computed from T in K: P2/P1 = T2/T1 = 373.15/283.15 = 1.32. Adding the vapour pressure, at 100C the pressure inside is 1.37 + 1.00 = 2.37 atm. This doesn't consider however the volume variation. Since some liquid water becomes vapour, the volume available for the gases increases and this reduces the air pressure, so the final result would be less than 2.37 atm.