Heterogeneous chemical equilibria system

The pseudohomogeneous chemical equilibrium (PCE) for the cyclohexanol reaction system is illustrated in Fig. 5.21a and the non-reactive isobaric L-L phase diagram is plotted in Fig. 5.21b. The rafSnate phase is very dose to the pure water vertex (see enlarged view in the right block). The two L-L envelopes intersect the PCE at two points x = (0.3466, 0.1840) and x = (0.0003, 0.9969). The two parts of the PCE outside the L-L region and the so called unique reactive liquid-liquid tie line [19] comprise the heterogeneous chemical equilibrium line (HCE), which is the bold line in Fig. 5.21b. 

Chemical equilibria with reactants and products that are all in the same phase are called homogeneous equilibria. Equilibria C, D, and E are homogeneous. Equilibria in systems having more than one phase are called heterogeneous equilibria. Equilibrium F is heterogeneous so too is the equilibrium between water vapor and liquid water in a closed system ... 

The kinetic factor is proportional to the energetic state of the system and (for heterogeneous catalytic systems) the number of active sites per unit volume (mass) of catalyst. The driving-force group includes the influence of concentration and distance from chemical equilibrium on the reaction rate, and the hindering group describes the hindering effect of components of the reaction mixture on the reaction rate. The kinetic factor is expressed as the rate constant, possibly multiplied by an equilibrium constant(s) as will be shown later. 

Chemical transport of solids is a well known preparative technique. As was pointed out by Schafer41, information on thermodynamic properties of heterogeneous systems can also be obtained from experiments involving chemical transport. In particular, the dependence of chemical equilibrium of a heterogeneous reaction of the type... 

The energy level diagrams, which can be compiled and used by any experimental chemist, represent a qualitative assessment of the dependence of chemical equilibrium composition of heterogeneous systems on the plasma parameters. The merit of such an approach is its simplicity. 

We now provide a preliminary discussion of chemical equilibrium in ideal heterogeneous systems. This treatment is provisional since the generalized approach of Section 7 of Chapter 3 is more systematic and does not require a distinction to be made... 

It is of course well known that in nature heterogeneous chemical equilibria are possible systems in which chemical reactions may take place, and which at equilibrium will exist in mote than one phase. The question that arises is the analysis of the conditions under which heterogeneous chemical equilibria are possible in multicomponent mixtures. In this section, we follow closely the analysis that was recently presented by Astarita and Ocone (1989) earlier work on the subject is due to Caram and Scriven (1976) and Astarita (1976). 

In systems where heterogeneous chemical equilibria prevail, both chemical and phase equilibrium conditions must be simultaneously satisfied. In practice, this means that the chemical equilibrium condition—Eq. (51) in the discrete description, and Eq. (60) in the continuous one—must be satisfied in one phase, and the phase equilibrium condition [/( or fi(x) to be the same in all phases] must be satisfied this clearly guarantees that the chemical equilibrium condition is automatically satisfied in all phases. 

CHEMICAL EQUILIBRIUM IN IDEAL HETEROGENEOUS SYSTEMS Lastly, we obtain 155... 

Several key questions must be answered initially in a study of reaction chemistry. First, is the reaction sufficiently fast and reversible so that it can be regarded as chemical-equilibrium controlled Second, is the reaction homogeneous (occurring wholly within a gas or liquid phase) or heterogeneous (involving reactants or products in a gas and a liquid, or liquid and a solid phase) Slow reversible, irreversible, and heterogeneous (often slow) reactions are those most likely to require interpretation using kinetic models. Third, is there a useful volume of the water-rock system in which chemical equilibrium can be assumed to have been attained for many possible reactions This may be called the local equilibrium assumption. 

During and after World War II, Horiuti continued his research in chemical kinetics and its applications. His results were compiled in a voluminous paper entitled A Method of Statistical-Mechanical Treatment of Equilibrium and Chemical Reactions (1948). This method is applicable both to heterogeneous and homogeneous systems. Horiuti and his co-workers further attempted to apply the method to the study of a number of chemical syntheses and reactions, such as ammonia synthesis and ethylene hydrogenation. Nearly all of his research papers were published in the Journal of the Institute for Catalysis, of which he was the chief editor. 

Chemical equilibrium in heterogeneous systems (from the thermodynamic standpoint) when capillary or electrical effects are of importance—Adsorption—Donnan s theory of membrane equilibria—Micelle theory of colloidal electrolytes... 

Gibbs was the first to prove that in a heterogeneous (multiphase) closed system, the chemical potential of every phase is equal to the chemical potential of the other phase, which is in equilibrium with it ... 

If a mixture consisting of one or more components possesses uniform physical and chemical properties throughout, it is said to be a single-phase, homogeneous system. If, however, a system consists of one or more parts that have different properties and are set apart from each other by bounding surfaces, so that the phases are mechanically separable, the system is heterogeneous. When equilibrium exists between the distinct parts of the system, this condition is known as heterogeneous equilibrium. 

What is a homogeneous equilibrium system Give an example of a homogeneous equilibrium reaction. What is a heterogeneous equilibrium system Write two chemical equations that represent heterogeneous equilibria. 

In this chapter we apply the general criteria for equilibrium developed in Chap. 6 to systems in which chemical reactions may occur. In Sec. 8-1, we present a general discussion of chemical equilibrium in homogeneous and heterogeneous systems. The concept of a progress variable is introduced, and the conditions for chemical equilibrium are derived. The equilibrium constant is defined, and some of its properties are developed. A discussion of the Le Chatelier-Braun principle applied to chemical reactions is presented. In Sec. 8-2, the results of Sec. 8-1 are applied to chemical reactions in mixtures of real gases. 

In the remaining portion of this section we discxiss the effect of uniform electrostatic fields on the properties of systems in heterogeneous or chemical equilibrium. A criterion for heterogeneous equilibrium in the presence of a uniform field is... 

In contrast to equilibrium thermodynamics, the thermodynamics of irreversible processes portray the application of thermodynamic methods as dynamic and therefore time-dependent procedures. The name Prigo-gine must be mentioned in relationship to this—he received for his work in this area the Nobel Prize in the year 1977. A new, very complex thermodynamics originated from his examination method for chemical reactions, and was developed by us, to come to a successful description of heterogenous multiphase polymer systems. This theory interprets crazing fracture energy dissipation and fracture mechanism in a totally new way on the basis of dissipative structures in polymer blends and their dynamics, For a list of abbreviations used in this section sec page 610,... 

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