Chapter 6: Fugacity
Fugacity is a measure of chemical potential that determines the tendency of a substance to prefer one phase over another. The phase with the lowest fugacity will be the most favorable for the system, then the substance minimizes Gibbs free energy.
Fugacity is a state function at fixed temperature. For an ideal gas, fugacity is equal to the pressure of the system, so it is just useful when dealing with real substances. Fugacity can describe the behavior of real gases, liquids and solids. It can be calculated according to the next equation:
Fugacity is a state function at fixed temperature. For an ideal gas, fugacity is equal to the pressure of the system, so it is just useful when dealing with real substances. Fugacity can describe the behavior of real gases, liquids and solids. It can be calculated according to the next equation:
According to statistical mechanics, the fugacity is one of the parameters that define the grand canonical ensemble. The grand canonical ensemble is a system that may exchange particles with the environment, it is calculated from the chemical potential and Boltzmann constant.
The fugacity coefficient is defined as the ration fugacity/pressure. For an ideal gas, the coefficient is equal to 1. If it is less than 1, the substance has less fugacity. If it is greater than 1, then the substance has more fugacity.
References: Department of Chemical Engineering, National Cheng Kung University. Fugacity. Recuperado de http://www.che.ncku.edu.tw/FacultyWeb/ChenBH/E340100%20Thermodynamics/Supplementary/Fugacity.pdf