Analza variaţiilor funcţiilor termodinamice în sisteme reale de tip „sare precipitată– soluție apoasă” [Articol]

Abstract

An original method was employed to investigate complex chemical equilibria in systems containing solid phases of varying nature and arbitrary composition, in the context of multiple secondary reactions occurring between the solid phase ions and the components of the saturated aqueous solution. The analysis considered secondary processes such as ligand protonation, metal ion hydrolysis, and the formation of neutral, protonated, and hydroxocomplexes. To systematically account for all coupled secondary reactions, the concept of a generalized reaction equation was introduced. This approach enables a more comprehensive and accurate thermodynamic interpretation of heterogeneous systems involving slightly soluble salts. Particular emphasis was placed on the influence of pH on the variations of thermodynamic functions, due to the critical role of hydrogen ions in the speciation and transformation of chemical species in aqueous media. The method offers a robust framework for evaluating the total change in thermodynamic functions in real systems of the “precipitate – aqueous solution” type, under conditions where classical approximations fail to capture the complexity of the interactions involved.