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Where γi is the activity coefficient of the ith component in the liquid phase, foi is fugacity of pure liquid i at system temperature T and pressure P, φi is fugacity coefficient of the ith species in the vapor phase. Fugacity takes the place of vapor pressure when the vapor fails to show ideal gas behavior, either because of high pressure or as a result of vapor phase association. The vapor phase fugacity coefficient can be neglected when the system pressure is low (e.g. < 100 psi) and the system temperature is not below a reduced temperature of 0.8. The pure-liquid fugacity is essentially equal to the vapor pressure at system temperature up to reduced temperature of 0.7.
Fugacity of pure liquid: For components whose critical temperature is greater than the system temperature
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Where fo is pure liquid fugacity, υ is fugacity coefficient for pure vapor at the system temperature T, Po is vapor pressure at that temperature, V is liquid molar volume, P is system pressure, and T is temperature. The exponential term is known as the "Poynting Correction". It is greater than unity if system pressure is greater than the vapor pressure. When the system temperature is above the critical temperature, generalized fugacity coefficient graphs can be used. The Henry's constant is γ-∞fo where γ-∞ is activity coefficient at infinite dilution.
K-value for Ideal Liquid Phase, Non-Ideal Vapor Phase: When the liquid phase is ideal,
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K-value for Ideal Vapor Phase, Non-Ideal Liquid Phase: When vapor phase is ideal,
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Where Pi is the vapor pressure of ith component.
Module for calculating relative volatility.
