Showing papers on "Mass action law published in 2021"

On the Thermodynamics of Solubilization

Abstract: The thermodynamic theory of solubilization has been formulated with introducing the notion of standard solubilization affinity. An important component of this notion is the Laplace capillary pressure represented in the phase interpretation of the hydrocarbon core of a normal micelle. The partition coefficient of a solubilisate is also interpreted both in terms of a mole fraction within the formalism of chemical thermodynamics and in terms of concentration within the formalism of statistical mechanics. In contrast to the widespread approach using fictitious micellar “pseudophase,” this interpretation is based on the real physical picture of solubilisate partition between micelles and an ambient solution. Moreover, an exact solution has been presented for the problem of the effect of solubilization on the value of the critical micelle concentration (CMC). The consideration is based on the mass action law and new methods of defining the CMC via the constant of this law, aggregation number, and solubilisate concentration. The cases of solubilization from saturated (when studying solubility) and unsaturated (with an arbitrary concentration) solutions have been analyzed. However, the same result has been obtained in all variants, namely, solubilization decreases the CMC.

Thermodynamics of Malonamide Aggregation Deduced from Molecular Dynamics Simulations

Abstract: The aggregation of malonamide extractants diluted in an aliphatic solvent phase has been studied in the presence of water by molecular dynamics simulation. Using association criteria based on distances between molecules and graphs theory, the aggregate distribution has been computed and the corresponding Gibbs energy of aggregates and mass action law constants have been determined. Finally, a model allowing us to the compute critical micelle concentration and osmotic data for a variable concentration of extractants, with or without a correction of the organic phase activity, was developed. It appears however that the accurate depiction of the aggregation allows modeling the thermodynamics of the solution even without an explicit calculation of the activity: both models give results in good agreement with the experiments.

Transition states and entangled mass action law

Abstract: The classical approaches to the derivation of the (generalized) Mass Action Law (MAL) assume that the intermediate transition state (i) has short life time and (ii) is in partial equilibrium with the initial reagents of the elementary reaction. The partial equilibrium assumption (ii) means that the reverse decomposition of the intermediates is much faster than its transition through other channels to the products. In this work we demonstrate how avoiding this partial equilibrium assumption modifies the reaction rates. This kinetic revision of transition state theory results in an effective ‘entanglement’ of reaction rates, which become linear combinations of different MAL expressions.