Journal: Transactions of The Luventicus Academy (Trans. Luv. Acad.)

ISSN 1666-7581 (online)

ISSN 1666-7573 (printed)

Volume: 2002

Issue: 1 (March)

Paper: 1

Pages: 1-22

Internal use code: 02TLA001i

PDF file: ftp.luventicus.org/papers/02TLA001i.pdf

Title: I. The Gibbs energy form of the Fundamental Equation for multi-phase multi-reaction systems within the physical approach

Author: Juan José Luetich

Abstract: A general Gibbs energy representation of the fundamental equation for multi-phase multi-reaction systems is presented. The integral expression of the Gibbs energy comprises of as many terms as variables which have been chosen to describe the composition. The simplest set of composition variables is the one used in the physical approach to equilibrium problems. Within this frame, the differential form of the Gibbs energy for closed systems consists of two terms, like that corresponding to systems with invariable composition. The central point of the argument is the following property: at given conditions, the stable equilibrium state of any system is the particular state for which the potential of "element" i , mui, is independent of the state of the "atoms" taken to carry out the variation dni that, keeping unchanged the remaining variables, produces the variation dG. To prove this, the interpretation of the employed composition variables is facilitated by using the complete Legendre transformation of G, homogeneous function of the vector n, instead of the traditional, mathematically equivalent method of Lagrange multipliers. No difference is made between physical and chemical aggregation, i.e. between phase and combination changes. A modification of the phase rule expression is also discussed.n este trabajo se presenta una forma general de la ecuación fundamental para sistemas multifásicos en equilibrio químico.

Keywords: fundamental equation; Gibbs energy; chemical potential; Chemical Thermodynamics; phase rule; Legendre transformations