Showing papers on "Mass action law published in 2005"

Thermodynamics of phase and chemical equilibrium in a strongly nonideal esterification system

Abstract: In this study, the reaction equilibrium of the reversible esterification of acetic acid with 1-butanol giving 1-butyl acetate and water was investigated. The entire composition space including the miscibility gap was covered at temperatures relevant for technical processes (353.15 K to 393.15 K). The experiments were carried out in a multiphase batch reactor with online gas chromatography and in a batch reactor with quantitative 1H NMR spectroscopy, respectively. The thermophysical database available in the literature was complemented by measurements of liquid−liquid and vapor−liquid equilibria. On the basis of that comprehensive data, thermodynamically consistent models of the reaction equilibrium were developed which predict the concentration dependence of the mass action law pseudoequilibrium constant, Kx. The following different modeling approaches are compared: the GE models NRTL and UNIQUAC as well as the PC-SAFT equation of state and the COSMO-RS model. All of them can successfully be used, the CO...

Ion exchange equilibria of arsenic in the presence of high sulphate and nitrate concentrations

Abstract: The aim of this work was to develop a quantitative description of the ion exchange equilibria of arsenic on a strong anionic resin, in the presence of nitrates and sulphates. First, the ion exchange equilibrium data of As(V) and NO - 3 on a strong anionic resin in chloride form were obtained and described with a model based on the mass action law. Namely, assuming ideal behaviour for both solution and resin phase, the thermodynamic constant of the As(V)/Cl - and NO - 3 /Cl - ion exchange equilibria were estimated by fitting of experimental data. Then, these equilibrium constants were used to predict the ion exchange behaviour of the ternary system As(V)/NO3 - /Cl - , providing a rather good agreement with experimental results. The ion exchange equilibria involving sulphate ions were also studied, showing a very high affinity to the resin phase. This behaviour did not allow a quantitative robust modelling of the equilibrium pattern. The results discussed in this paper represent a first step toward the development of a comprehensive modelling of the ion exchange process for the removal of As(V) from surface and groundwater in the presence of competitive, naturally occurring anions.

Concept of Ion Association in the Theory of Electrolyte Solutions

Abstract: Analytical solution of the associative mean spherical approximation (AMSA) and the modified version of the mean spherical approximation — the mass action law (MSA-MAL) approach for ion and ion-dipole models are used to revise the concept of ion association in the theory of electrolyte solutions. In the considered approach in contrast to the traditional one both free and associated ion electrostatic contributions are taken into account and therefore the revised version of ion association concept is correct for weak and strong regimes of ion association. It is shown that AMSA theory is more preferable for the description of thermodynamic properties while the modified version of the MSA-MAL theory is more useful for the description of electrical properties. The capabilities of the developed approaches are illustrated by the description of thermodynamic and transport properties of electrolyte solutions in weakly polar solvents. The proposed theory is applied to explain the anomalous properties of electrical double layer in a low temperature region and for the treatment of the effect of electrolyte on the rate of intramolecular electron transfer. The revised concept of ion association is also used to describe the concentration dependence of dielectric constant in electrolyte solutions.

Modeling the onset of asphaltene flocculation at high pressure by an association model

Abstract: A new thermodynamic model was developed to calculate the onset of flocculation in crude oil systems similarly to the liquid-liquid equilibrium of polymer solutions. The key concept of the model is that asphaltene self-association leads to a polydisperse system of associates characterized by a size distribution function. Using continuous thermodynamics the mass action law is applied to the association equilibrium and an analytical expression for the size distribution function is derived. In contrast to polymer thermodynamics this distribution function depends on temperature, pressure, and concentration. For modeling the high pressure equilibrium the Sako-Wu-Prausnitz equation of state is applied. The model was tested on existing flocculation data for three systems of the type methane + i-octane + maltene + asphaltene with crude oils of different asphaltene contents. The amount of precipitant necessary to provoke flocculation was calculated in good agreement with the experimental data for all three...

Manifestation of the equilibrium hole distribution in photoluminescence of n‐InN

Abstract: Photoluminescence (PL) of n-InN grown by molecular beam epitaxy with Hall concentrations from 3.6 to 7.3 × 1017 cm–3 demonstrates dependences on carrier concentration, temperature, and excitation density which give evidences of a fast energy relaxation rate of photoholes and their equilibrium distribution over localized states. The structure of the PL spectra observed at 4.2 and 77 K in the energy interval from 0.50 to 0.67 eV indicates that a considerable part of holes is trapped by deep and shallow acceptors before the interband recombi- nation with degenerate electrons occurs. At room temperature, the band-to-band recombination of free holes and electrons dominates in PL. Experimental results on PL and absorption are described by model calculations under the assumptions of a band gap equal to 0.665–0.670 eV at zero temperature and zero carrier concentration and a non-parabolic conduction band with the effective mass at the G-point equal to 0.07 of the free electron mass. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Deviations from the Mass Action Law in Non‐equilibrium Gas Flows

Abstract: In this paper, the relations between the rate coefficients of dissociation and recombination reactions in non‐equilibrium gas mixture flows are considered. It is shown that under thermal non‐equilibrium conditions, the mass action law is violated. The influence of state‐to‐state and two‐temperature vibrational distributions on the averaged non‐equilibrium factor, which characterizes a deviation from the mass action law, is estimated.

Study on Microcosmic Models of Equilibrium and Non-equilibrium Plasma

Abstract: In this paper, several present microcosmic models of plasma Potapov's model, Eindhoren model, the model based on dynamics, and the model based on minimum Gibbs free-enthalpy, are summarized and compared The fundamentals of the first two models are Dalton's law, mass action law, charge neutral law and stoichiometric equilibrium condition But they are different at the formula of mass action law and the partition equation The last two models describe the microcosmic process of the plasma, based on the chemical reaction, and the basic definitions of thermodynamics and statistical physics, respectively The variation of the models in the case of equilibrium and non-equilibrium condition is explained And the Eindhoven's model is recommended to be adopted in engineering application