Fugacity of species

Thus the fugacity of species / in an ideal gas mixture is equal to its partial pressure. 

Gamma/Phi Approach For many XT E systems of interest the pressure is low enough that a relatively simple equation of state, such as the two-term virial equation, is satisfactoiy for the vapor phase. Liquid-phase behavior, on the other hand, may be conveniently described by an equation for the excess Gibbs energy, from which activity coefficients are derived. The fugacity of species i in the liquid phase is then given by Eq. (4-102), written... 

Any cubic equation of state can give an expression for the fugacity of species i in a gaseous or in liquid mixture. For example, the expression for the... 

The fugacity of species B in an ideal solution of gases is given by the Lewis and Randall rule... 

Gravitational potential energy Fugacity of pure species i Fugacity of species i in solution... 

Consider a gas-phase reaction. If the Lewis and Randall mixing rules are used (simplest form of mixing rules—more sophisticated relationships could be applied if deemed necessary) to give for the fugacity of species i, fj ... 

Numerical values for the fugacities of species in liquid mixtures are readily calculated from experimental VLE data. According to Eq. (11.30),... 

Thus, the fugacity of species i (in both the hquid and vapor phases) is equal to the partial pressure of species i in the vapor phase. Its value increases from zero at infinite dilution (jc, = y, -> 0) to Pj for pnre species i. This is illnstrated by the data of Table 12.1 for the methyl ethyl ketone(l)/toluene(2) system at 323.15 K (50°C). The first tlnee columns list a set of experimental P-x -y data and colunms 4 and 5 show ... 

A where /,. and P are the fugacity of species i in the vapor mixture and the total pressure, respectively. From the thermodynamic equilibrium criteria, if the two phases of liquid and vapor are in a state of equilibrium, then ... 

The fugacity of species i in the mixture fi can be defined in terms of the pure species fugacity through an activity coefficient or a fugacity coefficient (f>i as will be explained shortly. 

Thus, to evaluate 77, we have only to calculate the pressures of homogeneous mixtures. The osmotic equilibrium condition can be expressed by writing that the chemical potentials, and therefore the fugacities of species s4 = 0,.. ., (, are equal on both sides of the membrane. On the solution side, we have... 

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