Equilibria in systems condensed substance–gas
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The information about the reasons for linearity of the empirical functions lnK°(T) = f(1/T) in the local temperature range, where K°(T) is polythermal data on equilibrium constants of homogenous and heterogeneous processes (in the latter case, if at least one chemical species presents among reagents), were generalized. During this work the conclusions obtained were used to develop a procedure of tensimetric evaluating thermodynamic parameters of individual substance evaporation process, realized in the area of co-producing two molecular species in saturated vapor composition (P exp = P 1 + P 2). In particular, it was shown that regression analysis of tensimetric data for these systems was informative due to admissibility of the linear model (for the functions lnP i(T) = f(1/T)) to describe the contribution of each of the molecular species in the measured pressure. In addition, it was shown the constructiveness of replacing the variable x = 1/T by x′ = ∆T/T = (T – T *)/T which was related with reassignment of conceptual meaning for the first of two liner parameters from the standard entropy of the evaporation reaction (∆r S iº*) to the standard Gibbs free energy (∆r G iº*) (the superscript * refers both of these characteristics and the value T * to the investigated temperature range center calculated in terms of inverse scale). The procedure developed allows ones to realize stable evaluating two pairs of thermodynamic characteristics of ∆r G iº* and ∆r H i * (i = 1, 2). The third pair (∆r S iº*) is strictly calculated using well-known fundamental relationship. Procedure informativity is particularly illustrated by a simple example (evaporation of SeO3solid in the temperature range 360–392 K).
KeywordsChemical species as reagent Thermodynamic characteristics Polythermal data Processing tensimetric data Vapor composition over SeO3solid
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