Gibbs function for processes in solution

CHANGES IN GIBBS FUNCTION FOR PROCESSES IN SOLUTIONS For this reaction... 

To finalize the development of the aqueous CO2 force field parameters, the C02 model was used in free energy perturbation Monte Carlo (FEP/MC) simulations to determine the solubility of C02 in water. The solubility of C02 in water is calculated as a function of temperature in the development process to maintain transferability of the C02 model to different simulation techniques and to quantify the robustness of the technique used in the solubility calculations. It is also noted that the calculated solubility is based upon the change in the Gibbs energy of the system and that parameter development must account for the entropy/enthalpy balance that contributes to the overall structure of the solute and solvent over the temperature range being modeled [17]. 

Without going into the details of the model, we note here that the study of Elkoshi and Ben-Naim focused on the function yss at contact distance (i.e. when two solutes s become nearest neighbors). This function is related to the solvent-induced part of the change in the Gibbs energy for the process of bringing the two solutes from infinite separation to the distance of nearest neighbors ... 

The activity coefficient of a component in a mixture is a function of the temperature and the concentration of that component in the mixture. When the concentration of the component proaches zero, its activity coefficient approaches the limiting activity coefficient of th component in the mixture, or the activity coefficient at infinite dilution, y . The limiting activity coefficient is useful for several reasons. It is a strictly dilute solution property and can be used dir tly in nation 1 to determine the equilibrium compositions of dilute mixtures. Thus, there is no reason to extrapolate uilibrium data at mid-range concentrations to infinite dilution, a process which may introduce enormous errors. Limiting activity coefficients can also be used to obtain parameters for excess Gibbs energy expressions and thus be used to predict phase behavior over the entire composition range. This technique has been shown to be quite accurate in prediction of vapor-liquid equilibrium of both binary and multicomponent mixtures (5). 

Extensive data also exist for the enthalpy of transfer of 1-1 electrolytes from water to non-aqueous solvents. These data are obtained in calorimetric experiments in which the enthalpy of solution is measured as a function of electrolyte concentration. The value of the enthalpy of solution per mole at infinite dilution is obtained by extrapolation. The enthalpy of transfer is defined in the same way as the Gibbs energy of transfer according to process (4.8.4). Thus, the standard enthalpy of transfer is given by... 

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