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Related to Fugacity: Chemical potential


A function used as an analog of the partial pressure in applying thermodynamics to real systems; at a constant temperature it is proportional to the exponential of the ratio of the chemical potential of a constituent of a system divided by the product of the gas constant and the temperature, and it approaches the partial pressure as the total pressure of the gas approaches zero.



a quantity used to calculate the properties of real gases by means of the thermodynamic relationships developed for ideal gases (seeGASES). The concept of fugacity was introduced by G. Lewis in 1901.

The fugacity f of a given gas or a given component of a gas mixture is a function of pressure p and temperature T and of the concentration of each component of a mixture. When the fugacity is substituted for the partial pressure in the thermodynamic equations for an ideal gas, the equations are rendered valid for a real gas under the conditions considered. Although this technique is a formal mathematical procedure, it is productive because the use of more complex equations of state for real gases entails substantial computational difficulties and may not provide the necessary accuracy, since any equation of state for a real gas is valid only within a specific range of values of p and T.

The ratio flp is called the fugacity coefficient; for an ideal gas, it is obviously equal to unity under any conditions. Thus, the difference between the value of flp and unity characterizes the extent to which a gas departs from the ideal state. The role of the fugacity of a gas with respect to the partial pressure of the gas is similar to the role of the activity of a component of a solution with respect to the concentration of the component.

Since the fugacity of a substance that forms or is a constituent of a condensed phase is equal to the fugacity of the substance in the saturated vapor of the phase, the fugacity may also be regarded as a value that quantitatively characterizes—for a given p, T, and phase composition—the ability of the substance to leave the phase.


See references under THERMODYNAMICS, CHEMICAL.


References in periodicals archive ?
An excellent review of solution theories of fugacity can be found in the text by Prausnitz et al.
The fugacity of pure substance can be calculated via the following well-known equation (Edmister and Lee, 1983):
The kinetic limit to the hydrogen fugacity is determined by the sequence of reactions required to remove hydrogen atoms from the surface as their concentration increases toward this theoretical value or upper limit.
where the fugacity coefficient of pure A, fA,pure, exhibits no dependence on mixture composition, and [[sigma].
The critical fugacity for surface adsorption of self-avoiding walks on the honeycomb lattice is 1 + %/2.
The central action of Canto XXIV is the instantaneous reduction to ashes, in order to be restored and start over again, like the phoenix, of Vanni Fucci, whose very name rings with vain fugacity (vanitas) and the fact that he was here (ci fu).
A method of urban ecological risk assessment: combining the multimedia fugacity model and GIS.
It then deals with the fugacity approach and the conventional approach to mass transfer, and describes individual mass transfer processes and the flux equations required for a quantitative expression.
The method is based on different ingredient fugacity (different boiling temperature).
Yuan, H, Little, JC, Marand, E, Liu, Z, "Using Fugacity to Predict Volatile Emissions from Layered Materials with a Clay/Polymer Diffusion Barrier.
H] in the single-phase Pd-H solid solution and [MATHEMATICAL EXPRESSION NOT REPRODUCIBLE IN ASCII] are the fugacity and pressure of hydrogen in the equilibrium gas; [MATHEMATICAL EXPRESSION NOT REPRODUCIBLE IN ASCII] is the fugacity coefficient.
Biser affirms that poetry and theology share the metaphorical dimension, but "poetry speaks in pictures owing to the fugacity of its subject matter, theology owing to its abundance" (cf.