Modeling phase or chemical reaction equilibrium with an equation of state, an unrealistic modeling

Abstract

The traditional chemical thermodynamics considered the chemical potential then fugacity of a component in a single-phase, open system is just the one of the component in a co-existing phase of an equilibrium, multi-component, multi-phase system or in an equilibrium, chemical reaction system and the fugacity can be calculated with the equation of state of the single-phase, open system. Therefore, the most common method to model phase or chemical reaction equilibrium is with an equation of state. Obviously, modeling phase or chemical reaction equilibrium with an equation of state requires to the single-phase, open system is equivalent to the co-existing phase or the equilibrium, chemical reaction system. However, there are significant differences in the thermodynamics properties between the single-phase, open system and the co-existing phase or the equilibrium, chemical reaction system. Therefore, the chemical potential then fugacity of a component in the single-phase, open system is impossible the one of the component in the co-existing phase or in the equilibrium, chemical reaction system. That is, the calculated fugacity of a component in a single-phase, open system with the equation of state of the single-phase, open system is impossibly the fugacity of the component in a co-existing phase of an equilibrium, multi-component, multi-phase system or in an equilibrium, chemical reaction system. Therefore, it is unrealistic to model phase or chemical reaction equilibrium with an equation of state. For this, we establish the chemical potential differential formula of a component in a co-existing phase and in an equilibrium, chemical reaction system to calculate phase or chemical reaction equilibrium. The calculated values of solubility in molar concentration within the framework of the present theory equals exactly the measured values of solubility in molar concentration by the experiments.