conservation equations for chemical elements in fluids with chemical reactions守恒方程化学元素与化学反应流体.pdf

Int. J. Mol. Sci. 2002 , 3, 76–86 Int. J. Mol. Sci. ISSN 1422-0067 /ijms/ Conservation Equations for Chemical Elements in Fluids with Chemical Reactions E. Pi˜na and S.M.T. de la Selva Department of Physics, Universidad Aut´onoma Metropolitana, Iztapalapa,P.O. Box 55-534, D.F., 09340, M´exico. E-mail: tere@xanum.uam.mx Received: 22 March 2001 / Accepted: 30 November 2002 / Published: 28 February 2002 Abstract: It is well known that when chemical reactions occur, the masses of the participating molecules are not conserved, whereas the masses of the nuclei of the chemical elements constituting these same molecules, are conserved. Within the con- text of non-equilibrium thermodynamics, the first fact is expressed by the differential balance equations, for the densities of the chemically reacting molecules, having a non zero source term. At the same time the conserved quantities like the total mass, charge and energy obey differential conservation equations, i.e with zero source term. In this paper, we show that in fluids with chemical reactions occurring in them, there are ad- ditional conserved quantities, namely densities associated to the fact that the masses of the chemical elements are conserved. The corresponding differential conservation equations are derived. The found out conserved densities, one for each involved chem- ical element are shown to be linear combinations of the densities of those reacting molecules containing the element, weighted with the number of atoms of the element in the species. It is shown that in order to find the co