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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.
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.
The following article is from The Great Soviet Encyclopedia (1979). It might be outdated or ideologically biased.



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.


The Great Soviet Encyclopedia, 3rd Edition (1970-1979). © 2010 The Gale Group, Inc. All rights reserved.
References in periodicals archive ?
They considered moderate and high pressure levels, and reported activity and fugacity coefficients of each component in the mixtures through Lewis rule and Redlich-Kwong state equation for carbon dioxide in vapor phase.
where [x.sub.gas] is the mole fraction of dissolved gas in the condensed phase (which will be zero for ice and can be computed from Henry's law for gases in liquid water at low and moderate pressures), [[phi].sub.vap.sub.w] is the fugacity coefficient of water in the equilibrium vapor, and y is the vector of mole fractions representing the equilibrium composition of the vapor phase.
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).
Modelling of pharmaceutical residues in Australian sewage by quantities of use and fugacity calculations.
We have predicted conditions (pressure, temperature, oxygen fugacity) necessary for stability of these new materials, and some planets, though probably not the Earth, may offer such conditions," added Oganov.
xC[O.sub.2] was converted into pC[O.sub.2] and the fugacity of C[O.sub.2] (fC[O.sub.2]) according to equations provided by Zeebe and Wolf-Gladrow (2001).