1. The problem statement, all variables and given/known data I'm given the molar enthalpy of a gas at various temperatures. For each temperature, the enthalpy at 1 bar and 100 bars of pressure is listed. The question: The gas moves through a tube. The pressure in the tube is 100 bar. When the gas exits the tube, the pressure is 1 bar. (Hint: the enthalpy is conserved). What is the lowest temperature at which some liquefaction takes place? 2. Relevant equations 3. The attempt at a solution The chart says that at 1 bar and 77 K (liquid), the gas' enthalpy is -3407 J. At 1 bar and 77 K (gas), the gas' enthalpy is 2161 J. I think I'm supposed to find the temperature in the 100 bar part at which some liquifaction takes place. I am just not sure whether to use the liquid enthalpy or the gas enthalpy. Once I know the enthalpy, I can get the temperature.