NEW APPROACH TO SENSITIVITY ANALYSIS OF MULTIPLE EQUILIBRIA IN SOLUTIONS

We consider multiple equilibria in solutions in which the interaction of n chemical species is described by means of m stoichiometrically in dependent reactions (SIRs). For the study of certain thermodynamic pro perties of such systems, in particular, for sensitivity analysis, it i s important to know the determinant DELTA of the Hessian matrix of the Gibbs energy, as a function of the extent of the SIRs. Any linear com bination of SIRs, in which (at least) m - 1 species are not involved, is called a Hessian response reaction (HR): Several properties of the HRs are pointed out, in particular, the equivalence of DELTA to the su m of contributions originating from each HR. The effect of temperature and pressure on chemical equilibria in ideal solutions is analysed. I t is shown that the sensitivity coefficient of a chemical species A(i) may be presented as a sum of contributions coming from all HRs in whi ch A(i) is involved. Each of these contributions is a product of the s toichiometric coefficient of A(i), the enthalpy or volume change of th e respective HR, and a concentration-dependent term which is always po sitive. It is also shown that the relaxation contribution to the heat capacity is a sum of contributions over all HRs.