Gibbs-Duhem equation

Gibbs-Duhem equation

      thermodynamic relationship expressing changes in the chemical potential of a substance (or mixture of substances in a multicomponent system) in terms of changes in the temperature T and pressure P of the system. The chemical potential μ represents the Gibbs free energy per molecule of the substance (described by the American mathematical physicist Josiah Willard Gibbs (Gibbs, J Willard)), and hence the change in μ is the amount of energy per molecule available to do work for a process (such as the chemical reaction in a car battery) at constant temperature and pressure. However, if the process is carried out at a different temperature or pressure (such as on a cold winter morning), then the chemical potential will also change for each substance according to the Gibbs-Duhem equation (so called because of additional research by the French physicist Pierre Duhem (Duhem, Pierre)). A combined application of the first and second laws of thermodynamics yields the equation N dμ = −S dT + V dP, where N is the number of molecules of the substance, S is the entropy of the system, and V the volume. If the chemical potential is known for each substance under one set of conditions, then this equation can be integrated to find the corresponding chemical potential under a different set of conditions and hence the amount of energy that the car battery can deliver.

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Universalium. 2010.

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  • Josiah Willard Gibbs — Infobox Scientist box width = 300px name = J. Willard Gibbs image size = 300px caption = Josiah Willard Gibbs birth date = birth date|1839|2|11|mf=y birth place = New Haven, Connecticut, USA death date = death date and… …   Wikipedia

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  • liquid — liquidly, adv. liquidness, n. /lik wid/, adj. 1. composed of molecules that move freely among themselves but do not tend to separate like those of gases; neither gaseous nor solid. 2. of, pertaining to, or consisting of liquids: a liquid diet. 3 …   Universalium

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