Partial exchange, thermodynamic

Thermodynamic and Kinetic Parameter Values. Values of Standard Electrode Potential (at 25 °C) and Exchange Current Density (at 80 °C) are Referenced to 101.3 kPa Gaseous Reactant Partial Pressure. 

In semiconducting oxides such as iron-doped SrTi03 (e.g., SrTio.8Feo.2O3) the conductivity depends thermodynamically on the oxygen partial pressure. In the thermodynamic equilibrium a metal oxide exchanges lattice oxygen Oq with the ambient gas phase. 

Figure 15. Thermodynamic activities (TMS data) for NaCl (-0-) and KCl in the Ki slag-alkali exchange process. The indicated reference state partial pressures were obtained from Ref. 36. Key P NaCl = 5 X atm P° KCl = 5 X...

In this catalyst system, addition of phosphine or decrease in partial pressure of CO (or of total pressure at constant synthesis-gas ratio) shifts the phosphine-carbon monoxide ligand-exchange equilibrium toward the phosphine-substituted species (right to left in scheme 8.13). A decrease in phosphine concentration or an increase in CO pressure shifts it in the opposite direction (left to right). Addition of base shifts equilibrium downward, from the acids to the anions. In the presence of phosphine in an at least moderate excess, thermodynamics strongly favors HCo(CO)3Ph over HCo(CO)4, but Co(CO)4" remains very strongly favored over Co(CO)3Ph under all conditions of practical interest. 

Adsorption from solution is an exchange process. Consequences of this "first law" pervade all attempts to define individual (or partial) isotherms. Any assumption made on the adsorption of component 1 involves an assumption regarding component 2 deriving an equation for 1 implies deriving an equation for 2. This is (or should be) reflected in all models, and all thermodynamics and statistical thermodynamics should be consistent with this principle. 

In Chapter 8, Zuyi Tao, in order to provide a better understanding of the ion-exchange behavior of amino acids, has compiled their particular acid-base properties, their solubility in water, their partial molal volumes, and their molal activity coefficients in water at 25 C. This information has been used in Gibbs-Donnan-based equations to facilitate a better understanding of the mechanism of amino acid uptake by ion exchangers at low and high solution concentration levels. Measurement of distribution coefficients and separation factors are also described. The eventual resolution of thermodynamic ion-exchange functions (AG, AH, and AS) is provided for the reader. 

Ward (24) has suggested that with ZnX the active centers are essentially Bronsted acid sites associated with residual hydroxyl groups. -Partial hydration could promote movement of cations and result in the formation of additional such sites. The activity of the ZnX-IV zeolite can be explained satisfactorily in this manner, but with ZnX-I other factors must be involved. It is possible that with the higher exchanged zeolite, the increase in surface cations provides stronger adsorption sites for the butenes. If this were the case, then a slow rate of desorption of the products (relative to the surface reaction) could allow the 2-butene product ratio to approach that of thermodynamic equilibrium (13). 

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