Solvent activity calculation

The program produces in its output dataset a block of results that shows the concentration, activity coefficient, and activity calculated for each aqueous species (Table 6.4), the saturation state of each mineral that can be formed from the basis, the fugacity of each such gas, and the system s bulk composition. The extent of the system is 1 kg of solvent water and the solutes dissolved in it the solution mass is 1.0364 kg. 

Calculation of Activity of Solvent from That of Solute... 

In contrast, the acid-catalyzed hydrolysis of alkyl selenates is A-2158. The actual species which undergoes decomposition to alcohol and sulfur trioxide is probably the zwitterion as in the case of phosphate monoester monoanions. Evidence for sulfur trioxide as the reactive initial product of the A-1 solvolysis is obtained from the product compositions arising with mixed alcohol-water solvents. The product distribution is identical to that found for sulfur trioxide solvolysis, with the latter exhibiting a three-fold selectivity for methanol. Although the above entropies of activation and solvent deuterium isotope effects do not distinguish between the conventional A-l mechanism and one involving rate-limiting proton transfer, a simple calculation, based on the pKa of the sulfate moiety and the fact that its deprotonation is diffusion controlled. 

Thus, firstly, the choice of the pure solvent as the reference state for the definition of activities of solutes in fact impairs a fair comparison of the activity of dilute solutes such as general adds to the activity of the solvent itself. Secondly, the observed first-order rate constants k or k0 for the reaction of a solute with the solvent water are usually converted to second-order rate constants by division through the concentration of water, h2o = oA iho, for a comparison with the second-order rate coefficients HA. Again, it is questionable whether the formal h2o coefficients so calculated may be compared with truly bimolecular rate constants kUA for the reactions with dilute general acids HA. It is then no surprise that the values for the rate coefficients determined for the catalytic activity of solvent-derived acids scatter rather widely, often by one or two orders of magnitude, from the regression lines of general adds.74... 

Rabbe, C., Sella, C., Madic, C., Godard, A. 1999. Molecular modeling study of uranyl nitrate extraction with monoamides. II. Molecular mechanics and lipophilicity calculations. Structure-activity relationships. Solvent Extr. Ion Exch. 17 (1) 87-112. 

Solute and Solvent Activity Calculations. For the purposes of this study, the derivations necessary to the calculation of the solute and solvent activities will begin with the equation for the prediction of the excess free energy of a single electrolyte solution based on the work of Friedman (9). 

The Solvent Activity Calculation. A series of measurements on a Great Salt Lake (GSL) brine concentration sequence showed that the saturation vapor pressure lowering over a GSL brine at or near the labile saturation point should be about 9.5 millibars at 25°C. Application of the model to comparable GSL brine resulted... 

Calculated at 100°C from the reported activation parameters. " Solvent was not specified. 

Kharkats first calculated the energy of activation and solvent reorganization of charge transfer across the interface between two immiscible liquids [6,7,162]. The expression for the probability of electron transfer can be written as... 

Theories and models are presented below without going into details and without claiming completeness, since this text is not dedicated to theoretical problems but will only provide some help to calculate solvent activities. 

Today, there are two principal ways to develop an equation of state for polymer solutions first, to start with an expression for the canonical partition function utilizing concepts similar to those used by van der Waals (e.g., Prigogine, Flory et al., Patterson, Simha and Somcynsky, Sanchez and Lacombe, Dee and Walsh,Donohue and Prausnitz, Chien et al. ), and second, which is more sophisticated, to use statistical thermodynamics perturbation theory for freely-jointed tangent-sphere chain-like fluids (e.g., Hall and coworkers,Chapman et al., Song et al. ). A comprehensive review about equations of state for molten polymers and polymer solutions was given by Lambert et al. Here, only some resulting equations will be summarized under the aspect of calculating solvent activities in polymer solutions. 

Adidharma and Radosz provides an engineering form for such a copolymer SAFT approach. SAFT has successfully applied to correlate thermodynamic properties and phase behavior of pure liquid polymers and polymer solutions, including gas solubility and supercritical solutions by Radosz and coworkers Sadowski et al. applied SAFT to calculate solvent activities of polycarbonate solutions in various solvents and found that it may be necessary to refit the pure-component characteristic data of the polymer to some VLE-data of one binary polymer solution to calculate correct solvent activities, because otherwise demixing was calculated. GroB and Sadowski developed a Perturbed-Chain SAFT equation of state to improve for the chain behavior within the reference term to get better calculation results for the PVT - and VLE-behavior of polymer systems. McHugh and coworkers applied SAFT extensively to calculate the phase behavior of polymers in supercritical fluids, a comprehensive summary is given in the review by Kirby and McHugh. They also state that characteristic SAFT parameters for polymers from PVT-data lead to... 

We note that the PHSC equation of state is again an equation where three parameters have to be fitted to thermodynamic properties o, e/k and r. These may be transformed into macroscopic reducing parameters for the equation of state by the common relations T =e/k, P = 3eJ2vx and V = 2jiro /3. Parameter tables are given in Refs. PHSC was successfully applied to calculate solvent activities in polymer solutions, Gupta and Prausnitz. Lambert et al. found that it is necessary to adjust the characteristic parameters of the polymers when liquid-liquid equilibria should correctly be calculated. 

Knoevenagel condensation between benzaldehyde and activated methylene compounds (e.g. ethyl acetoacetate or ethyl cyanoacetate) catalysed by the proton sponge 1,8-bisdimethylaminonaphthalene has been studied and discussed with reference to results of quantum mechanical calculations. Solvent polarity is an important consideration since the catalyst may stabilize the methylene compound and thereby limit the rate of proton transfer to the condensed product. 

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