Theory for the determination of activity coefficients of strong electrolytes with regard to concentration dependence of hydration numbers

Afanas'ev, V. N.; Zaitsev, A. A.; Ustinov, A. N.; Golubev, Vasiliy A.

doi:10.1016/j.jct.2008.10.003

Cited by 5 publications

(5 citation statements)

References 8 publications

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“…13 Unfortunately, the conclusions of the given paper are based on the assumption that hydration numbers are independent of concentration, which runs contrary to our latest research. 14 To take into account the experimentally observed dependence of solvation numbers, an expression was proposed 15 for that part of the Gibbs energy which is connected with the changes occurring in hydration shells of ions as the concentration of an electrolyte increases…”

Section: Ionàdipole Interactions In the Gibbs Free Energymentioning

confidence: 99%

“…To take into account the experimentally observed dependence of solvation numbers, an expression was proposed for that part of the Gibbs energy which is connected with the changes occurring in hydration shells of ions as the concentration of an electrolyte increases Δ G 2 = λ N 2 ( normalΔ h ) 3 / 2 where N 2 is the number of electrolyte molecules; Δ h is the difference between the solvation number at infinite dilution h 0 and the solvation number h corresponding to the given concentration x 2 ; and λ is a constant independent of the concentration.…”

Section: Ion–dipole Interactions In the Gibbs Free Energymentioning

confidence: 99%

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Solvation of Electrolytes and Nonelectrolytes in Aqueous Solutions

Afanas'ev

2011

J. Phys. Chem. B

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A new theory of electrolyte and nonelectrolyte solutions has been developed which, unlike the Debye-Hückel method applicable for small concentrations only, makes it possible to estimate thermodynamic properties of a solution in a wide range of state parameters. One of the main novelties of the proposed theory is that it takes into account the dependence of solvation numbers upon the concentration of solution, and all changes occurring in the solution are connected with solvation of the stoichiometric mixture of electrolyte ions or molecules. The present paper proposes a rigorous thermodynamic analysis of hydration parameters of solutions. Ultrasound and densimetric measurements in combination with data on isobaric heat capacity have been used to study aqueous solutions of electrolytes NaNO3, KI, NaCl, KCl, MgCl2, and MgSO4 and of nonelectrolytes urea, urotropine, and acetonitrile. Structural characteristics of hydration complexes have been analyzed: hydration numbers h, the proper volume of the stoichiometric mixture of ions without hydration shells V(2h), compressibility β(1h), and the molar volume of water in hydration shells V(1h), their dependencies on concentration and temperature. It has been shown that for aqueous solutions the electric field of ions and molecules of nonelectrolytes has a greater influence on the temperature dependence of the molar volume of solution in hydration shells than a simple change of pressure. The cause of this effect may be due to the change in the dielectric permeability of water in the immediate vicinity of hydrated ions or molecules. The most studied compounds (NaCl, KCl, KI, MgCl2) have been studied in a wider range of solute concentrations of up to 4-5 mol/kg. Up to the complete solvation limit (CSL), the functions V(1h) = f(T) and β(1h) = f(T) are linear with a high correlation factor, and the dependence Y(K,S) = f(β1V1*) at all investigated concentrations of electrolytes and nonelectrolytes up to the CSL enables h and β(h)V(h) to be determined on the basis of relationships obtained in the study. The behavior of nonelectrolyte solutions is no different from that of electrolyte solutions, although it is possible to trace the difference between hydrophobic and hydrophilic interactions.

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Section: Ionàdipole Interactions In the Gibbs Free Energymentioning

confidence: 99%

Section: Ion–dipole Interactions In the Gibbs Free Energymentioning

confidence: 99%

Solvation of Electrolytes and Nonelectrolytes in Aqueous Solutions

Afanas'ev

2011

J. Phys. Chem. B

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“…where Δμ o w is the difference in chemical potential between pure liquid water and water in a fictitious, empty hydrate lattice at the reference conditions (P o , T o ) and ƒ j is the fugacity of hydrate forming gas j, which is computed from the eTBEOS. In the hydrate calculations, the reference conditions are P o = 101 325 Pa and T o = 273.15 K. For a more detailed discussion on the solution of Equation (11), readers are directed to the works of Garcia et al [71] and by Michel and Clarke. [72] Table 4 provides a summary of the results of the hydrate equilibrium calculations, while Figures 4-7 illustrate some of the results.…”

Section: Computation Of Gas Hydrate Formation Conditions In Multi-sal...mentioning

confidence: 99%

“…A review of activity coefficient models for aqueous electrolyte systems is outside the scope of this work; however, interested readers are encouraged to consult the seminal works by Debye and Hückel, [1] Pitzer, [2] or one of many more recent works. [3][4][5][6][7][8][9][10][11][12][13] Whereas activity coefficient models are typically derived from Gibbs energy models, equations of state for aqueous electrolyte solutions are typically derived from Helmholtz energy models, which consist of both non-electrolyte and electrolyte contributions. The non-electrolyte term is most commonly modelled by a cubic equation of state [14][15][16][17][18][19][20][21][22][23][24][25][26][27] or by a variant of the Statistical Associating Fluid Theory equation of state.…”

Section: Introductionmentioning

confidence: 99%

Extension of the electrolyte Trebble–Bishnoi EOS to mixed‐salt systems, and application to vapour liquid and solid (hydrate) vapour liquid equilibrium calculations

Clarke

2022

Can J Chem Eng

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“…However, the experiments and calculations presented in this paper are based on concentrations. The difference between concentration and activity is determined by the activity coefficient, which is difficult to determine experimentally [22]. By default, this difficulty is circumvented by working with constant ionic strength, since the activity coefficients are largely dependent on it, and equilibrium constants can thus be more easily recorded.…”

Section: Introductionmentioning

confidence: 99%

Stabilization of the Computation of Stability Constants and Species Distributions from Titration Curves

et al. 2021

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Thermodynamic equilibria and concentrations in thermodynamic equilibria are of major importance in chemistry, chemical engineering, physical chemistry, medicine etc. due to a vast spectrum of applications. E.g., concentrations in thermodynamic equilibria play a central role for the estimation of drug delivery, the estimation of produced mass of products of chemical reactions, the estimation of deposited metal during electro plating and many more. Species concentrations in thermodynamic equilibrium are determined by the system of reactions and to the reactions’ associated stability constants. In many applications the stability constants and the system of reactions need to be determined. The usual way to determine the stability constants is to evaluate titration curves. In this context, many numerical methods exist. One major task in this context is that the corresponding inverse problems tend to be unstable, i.e., the output is strongly affected by measurement errors, and can output negative stability constants or negative species concentrations. In this work an alternative model for the species distributions in thermodynamic equilibrium, based on the models used for HySS or Hyperquad, and titration curves is presented, which includes the positivity of species concentrations and stability constants intrinsically. Additionally, in this paper a stabilized numerical methodology is presented to treat the corresponding model guaranteeing the convergence of the algorithm. The numerical scheme is validated with clinical numerical examples and the model is validated with a Citric acid–Nickel electrolyte. This paper finds a stable, convergent and efficient methodology to compute stability constants from potentiometric titration curves.

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Theory for the determination of activity coefficients of strong electrolytes with regard to concentration dependence of hydration numbers

Cited by 5 publications

References 8 publications

Solvation of Electrolytes and Nonelectrolytes in Aqueous Solutions

Solvation of Electrolytes and Nonelectrolytes in Aqueous Solutions

Extension of the electrolyte Trebble–Bishnoi EOS to mixed‐salt systems, and application to vapour liquid and solid (hydrate) vapour liquid equilibrium calculations

Stabilization of the Computation of Stability Constants and Species Distributions from Titration Curves

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