A residual property of a pure gas or gaseous mixture represents the value of the property relative to an ideal gas or ideal gas mixture at the same temperature or pressure. So the word residual applies to gases.maistral said:Summary:: The title.
I am getting confused as these three kinds of 'enthalpies' keep on appearing in the literature I am reading. How are they different? From what I can understand, they are all deviations from ideality, and that they can be 'estimated' using an equation of state. Other than that, how do they differ from each other?
Departure enthalpy, excess enthalpy, and residual enthalpy are all thermodynamic properties that describe the behavior of a substance during a phase change. Departure enthalpy is the difference between the enthalpy of a substance at a given state and its ideal gas enthalpy at the same temperature and pressure. Excess enthalpy is the difference between the enthalpy of a mixture and the enthalpy of its individual components at the same temperature and pressure. Residual enthalpy is the difference between the enthalpy of a substance in its real state and its ideal gas enthalpy at the same temperature and pressure.
Departure enthalpy, excess enthalpy, and residual enthalpy are typically calculated using thermodynamic equations and data from experiments. These properties can also be calculated using thermodynamic software or tables of thermodynamic data.
Departure enthalpy, excess enthalpy, and residual enthalpy are important in understanding the behavior of substances during phase changes, such as boiling or condensation. They also play a role in the design and optimization of thermodynamic processes and systems.
Yes, departure enthalpy, excess enthalpy, and residual enthalpy can be negative. A negative value indicates that the substance has a lower enthalpy in its real state compared to its ideal gas state at the same temperature and pressure.
The values of departure enthalpy, excess enthalpy, and residual enthalpy are dependent on temperature and pressure. These properties generally increase with increasing temperature and decrease with increasing pressure, but the exact relationship can vary depending on the substance and the phase change being studied.