Mass action constant

Effects of Cold Gas Recycle and Approach to Equilibrium. Product gases resulting from various CGR ratios were analyzed (Table XI). For the experiments tabulated, a decrease in the cold recycle ratio resulted consistently in increases in the product gas concentrations of water vapor, hydrogen, and carbon dioxide and a decrease in methane concentration. These trends may be noted in experiment HGR-12 as the CGR ratio decreased from 8.7 1 to 1.2 1, in experiment HGR-13 as it increased from 1.0 1 to 9.1 1, and in experiment HGR-14 as it decreased from 3.0 1 to 1.0 1. These trends indicate that the water-gas shift reaction (CO + H20 —> C02 + H2) was sustained to some degree. Except for the 462-hr period in experiment HGR-14, the apparent mass action constants for the water-gas shift reaction (based on the product gas compositions in Table XI) remained fairly constant at 0.57-1.6. These values are much lower than the value of 11.7 for equilibrium conversion at 400°C. In... 

The ion-exchange constants, K, in (7) should be related to the individual mass action constants, K land Ky, and this seems to be correct, based on limited evidence and some major approximations (Bunton et al., 1983a). A recent and more detailed data analysis shows that the value of the ion-exchange constant is consistent with values of the individual constants (Rodenas and Vera, 1985). 

Fig. 2.7. Calculated mass action constant K(T) serves to estimate dimer concentrations in hydrogen, methane, carbon dioxide and sulfur hexafluoride as function of temperature.

The right-hand side of (3.102) is a temperature- and density-dependent mass-action constant K(nT), which reads [with Aab = h/(2fjLabkBT)112, fiab being the reduced mass)... 

Defect chemical parameters and transport coefficients of 9.5 mol% Y203 -stabilized Zr02 a according to Ref.84 The mass action constants are apparent values that include activity coefficients and vary with the Y-content.84 Reprinted from K. Sasaki and J. Maier, Solid State Ion., 134 (2000), 303-321. Copyright 2000 with permission from Elsevier. 

Here, +i[S] serves as the apparent mass-action rate constant for the conversion E — ES. Each time an enzyme cycles from state E to ES and back to E again, one molecule of S is converted to P. If the rate of turnover of the catalytic cycle is significantly greater than the rate of change of reactant (S and P) concentrations, then the apparent mass-action constant +i[S] in Equation (4.2) remains effectively constant over the timescale of the catalytic cycle. This is true, for example, when the enzyme concentration is small compared to reactant concentrations, many catalytic cycles are required to produce a significant change in reactant concentrations. 

In Chapter 3 we determined the conditions under which it is and is not appropriate to treat a reaction as irreversible. Using the notation of cycle kinetics and apparent mass-action constants, the reversible mechanism of Equation (3.25) is represented... 

Let us explicitly consider an oxide MO and assume that only oxygen defects can be formed to a perceptible extent, then we have to consider the set of internal and external equations given by Table 1. (Note that one disorder reaction is redundant in Table 1.) The free parameters are obviously (i) the temperature which enters the mass action constants (see Table 1) and (ii) the partial pressure Px2 which... 

PbO is an example of I-regime and exhibits mixed conduction,47 48 oion is constant since the decisive ionic defect concentration ([O, ]) is determined by the square of the mass action constant of the ionic disorder reaction. (In PbO very probably the counter-defect to Oj is Pb rather than v0 the results, however, are not different then). Owing to Eq. (22), [e ] oc P M, [h ] °c Pq /4. ... 

Selectivity coefficients are not generally constant over the whole exchange isotherm since their definition incorporates concentrations rather than activities. The relation between the thermodynamic exchange constant (/Cth) the mass action constant on a particular concentration scale is obtained by introducing activity coefficients into the expression for the selectivity coefficient, thus ... 

Bjerrum (Bj) combined the Arrhenius and DH approaches by assuming a chemical equilibrium between ion-pairs and free ions [27], This concept takes into account interactions of ions at short range, which are not adequately described in DH theory. It also includes a theory for the mass action constant as a function of the dielectric constant e of the solvent. Many experimental investigations of the electrical conductance A, e.g. reviewed by Kraus [36], have confirmed Bjerrum s concept, which is the basic concept of many modern approaches. 

Calculation of Mass Action Constant at Different Temperatures... 

I Current in amperes j Cell constant K Constant k Conductance K Mass action constant k Boltzmann s constant L Length... 

This method yields the value 0.531 for the thermodynamic mass action constant K. A hypothetical cell of the form... 

The complexes ABA+ and BAB are called triple ions. The mass action constants for the two equilibria are assumed to have the same value, thus... 

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