Fugacity coefficient defined

A particular method for emphasizing the deviation from ideality is to introduce the so-called activity coefficient or fugacity coefficient defined by yi = ft/Pi, so as to rewrite Eq. (3.1.4a) in the form... 

The fugacity of the vapor phase can be accurately represented in terms of a fugacity coefficient defined by Eq. (12). For an ideal gas, tpi = the... 

On the other hand, when they form a nonideal solution, the fugacity coefficient is replaced by the partial fugacity coefficient defined as... 

Fugacity coefficients define the deviation from non-ideal to ideal gas behavior and can be determined from generalized compressibility charts or from suitable equations of state [e.g., Soave-Redlich-Kwong, Eq. (6.11.61) for details see Soave (1972)] ... 

One can also define an activity coefficient or fugacity coefficient y =flp, obviously... 

The fugacity coefficient of thesolid solute dissolved in the fluid phase (0 ) has been obtained using cubic equations of state (52) and statistical mechanical perturbation theory (53). The enhancement factor, E, shown as the quantity ia brackets ia equation 2, is defined as the real solubiUty divided by the solubihty ia an ideal gas. The solubiUty ia an ideal gas is simply the vapor pressure of the sohd over the pressure. Enhancement factors of 10 are common for supercritical systems. Notable exceptions such as the squalane—carbon dioxide system may have enhancement factors greater than 10. Solubihty data can be reduced to a simple form by plotting the logarithm of the enhancement factor vs density, resulting ia a fairly linear relationship (52). 

Another property which can be represented by generalized charts is fugacity, ( ). The fugacity of a substance can be regarded as a corrected vapor pressure. At low pressures (below atmospheric) the use of pressure in the place of fugacity leads to tittle error in calculations. The fugacity coefficient is defined by... 

When i = J, all equations reduce to the appropriate values for a pure species. When i j, these equations define a set of interaction parameters having no physical significance. For a mixture, values of By and dBjj/dT from Eqs. (4-212) and (4-213) are substituted into Eqs. (4-183) and (4-185) to provide values of the mixture second virial coefficient B and its temperature derivative. Values of and for the mixture are then given by Eqs. (4-193) and (4-194), and values of In i for the component fugacity coefficients are given by Eq. (4-196). 

A generally apphcable alternative to the gamma/phi approach results when both the hquid and vapor phases are described by the same equation of state. The defining equation for the fugacity coefficient, Eq. (4-79), may be applied to each phase ... 

The fugacity of a component i in a gas mixture is related to the total pressure P and to its mole fraction yt through the fugacity coefficient [Pg.144]

Thus, equilibrium is achieved when the escaping tendency from the vapor and liquid phases for Component i are equal. The vapor-phase fugacity coefficient, fj, can be defined by the expression ... 

The liquid-phase fugacity coefficient

[Pg.60]

The terms fugacity, activity and activity coefficient defined ... 

According to this definition f is equal to the partial pressure P, in the case of an ideal gas. The fugacity coefficient (j>- is defined by... 

Another useful term is fugacity coefficient. Fugacity coefficient for each component of a mixture is defined as the ratio of fugacity to partial pressure. 

The exact definition of the equilibrium constant given by IUPAC requires it to be defined in terms of fugacity coefficients or activity coefficients, in which case it carries no units. This convention is widely used in popular physical chemistry texts, but it is also common to find the equilibrium constant specified in terms of molar concentrations, pressure or molality, in which cases the equilibrium constant will carry appropriate units. 

PI 1.5 Start with the defining equations for the fugacity / and the fugacity coefficient equations (11.36), (11.37), and (11.38), along with the relationships given in Table 11.1, and show that 4> is related to the compressibility factor z by equation (11.44)... 

Both of these integrands are infinite at their lower limit, and the integrals cannot be evaluated. To circumvent this difficulty, we define the fugacity coefficient, , so that... 

We also define the fugacity coefficient [Pg.66]

Also the activity coefficient, fB, (underlined to avoid its confusion with fugacity) is defined by the equation ... 

An alternative form of Eq. (11.30) results from introduction of the fugacity coefficient, as defined by Eq. (11.33) ... 

These quantities are not in general dimensionless. One can define in an analogous way an equilibrium constant in terms of fugacity Kf, etc. At low pressures Kp is approximately related to K by the equation K Kp/(p )lv, and similarly in dilute solutions Kc is approximately related to K by K Kc/(c )lv however, the exact relations involve fugacity coefficients or activity coefficients [24]. 

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