The nature of single-ion activity coefficients calculated from potentiometric measurements on cells with liquid junctions

Zarubin, Dmitri P.

doi:10.1016/j.jct.2011.02.022

Cited by 39 publications

(13 citation statements)

References 52 publications

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“…The striking features, which are apparent from these figures, are that the proton activity coefficient from MC is the lowest whereas the chloride ion activity coefficient is the highest compared with the experimental values [25]. In a recent study Quinones et al [56] applied a modified Poisson-Boltzmann theory and obtained good agreement with our simulation data for single and mean activity coefficients of 1:1, 2:1 and 3:1 electrolytes.…”

Section: Figsupporting

confidence: 79%

“…On the experimental side there have been a number of reports in recent literature where single ion activities measured by ion selective electrodes have been reported [19][20][21][22][23]. However, the measurements of single ion activities by ion sensitive electrodes has been criticized in the literature [24,25]. The criticism was based on the one of pioneering comments made by Guggenheim [26] stating that "single ion activities cannot be measured" and the debate whether they can be measured or not by ion selective electrodes is still going on [27][28][29].…”

Section: Introductionmentioning

confidence: 99%

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Activity Coefficients of Concentrated Salt Solutions: A Monte Carlo Investigation

Abbas

Ahlberg

2019

J Solution Chem

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Monte Carlo (MC) simulations were used to calculate single ion and mean ionic activity coefficients and water activity in concentrated electrolytes and at elevated temperatures. By using a concentration dependent dielectric constant, the applicability range of the MC method was extended to 3 mol·L −1 or beyond, depending on the salt. The calculated activity coefficients were fitted to experimental data by adjusting only one parameter, i.e., the cation radius. Fitted ionic radii obtained by such a procedure indicate the extent of cationanion interaction in a salt solution. For example, the fitted radii of Li + and Na + in LiClO 3 and NaClO 3 indicate that Li + is strongly hydrated and has a weak interaction with the ClO 3 − ion whereas Na + forms ion pairs and loses its hydration. The single ion activity coefficients for protons and chloride ions in HCl were calculated by MC simulations and compared with experimental values obtained by ion selective electrodes. The calculated single ion activity coefficients for protons and chloride ions are much lower and higher, respectively, than the experimental values. However, the mean activity coefficients of HCl obtained by the MC simulations, ion selective electrodes and vapor pressure measurements are in good agreement. In the case of NaCl and KCl the calculated single ion activity coefficients of Na + , K + , and Cl − are much closer to the values obtained by ion selective electrodes. The results in HCl indicate that the hydrated proton is large and includes the chloride ion within the hydration shell, i.e., the apparent size of the chloride ion is negligible.

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Section: Figsupporting

confidence: 79%

Section: Introductionmentioning

confidence: 99%

Activity Coefficients of Concentrated Salt Solutions: A Monte Carlo Investigation

Abbas

Ahlberg

2019

J Solution Chem

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“…These measurements are strongly debated by other experimentalists [54,55,56,57,58,119,121,122]. Being theorists, we do not feel ourselves competent to judge in this debate; we just show the data.…”

mentioning

confidence: 92%

Unraveling the Behavior of the Individual Ionic Activity Coefficients on the Basis of the Balance of Ion–Ion and Ion–Water Interactions

Valiskó

Boda

2015

J. Phys. Chem. B

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We investigate the individual activity coefficients of pure 1:1 and 2:1 electrolytes using our theory that is based on the competition of ion-ion (II) and ion-water (IW) interactions (Vincze et al., J. Chem. Phys. 133, 154507, 2010). The II term is computed from Grand Canonical Monte Carlo simulations on the basis of the implicit solvent model of electrolytes using hard sphere ions with Pauling radii. The IW term is computed on the basis of Born's treatment of solvation using experimental hydration free energies. The two terms are coupled through the concentration-dependent dielectric constant of the electrolyte. With this approach we are able to reproduce the nonmonotonic concentration dependence of the mean activity coefficient of pure electrolytes qualitatively without using adjustable parameters. In this paper, we show that the theory can provide valuable insight into the behavior of individual activity coefficients too. We compare our theoretical predictions against experimental data measured by electrochemical cells containing ion-specific electrodes. As in the case of the mean activity coefficients, we find good agreement for 2:1 electrolytes, while the accuracy of our model is worse for 1:1 systems. This deviation in accuracy is explained by the fact that the two competing terms (II and IW) are much larger in the 2:1 case so errors in the two separate terms have less effects. The difference of the excess chemical potentials of cations and anions (the ratio of activity coefficients) is determined by asymmetries in the properties of the two ions: charge, radius, and hydration free energies.

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“…This relation was first identified by Malatesta [62] by Zarubin [7], and commented on by the authors of this text [8,24]. There are many details that necessarily have been left out of the discussion here.…”

Section: Fraenkel's Smaller-ion Shell Theorymentioning

confidence: 70%

“…The data of Sakaida and Kakiuchi [52] plotted together with their error limits and the data of Schneider et al [51] seemed to be in mutual agreement. This relation, until now, has only been explored in a correlational form [7,10,28]. Summarizing, with the exception of data for the HCl system, there is good agreement between the values of the activity coefficients of individual ions reported by different laboratories using very different methods for collecting the data.…”

Section: Comparison Of Experimental Results For the Activity Of Indivmentioning

confidence: 99%

Chapter 27 The Activity of Individual Ions Measuring and Modeling

Vera¹,

Wilczek-Vera²

2016

Classical Thermodynamics of Fluid Systems

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The nature of single-ion activity coefficients calculated from potentiometric measurements on cells with liquid junctions

Cited by 39 publications

References 52 publications

Activity Coefficients of Concentrated Salt Solutions: A Monte Carlo Investigation

Activity Coefficients of Concentrated Salt Solutions: A Monte Carlo Investigation

Unraveling the Behavior of the Individual Ionic Activity Coefficients on the Basis of the Balance of Ion–Ion and Ion–Water Interactions

Chapter 27 The Activity of Individual Ions Measuring and Modeling

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