Gibbs energies of transfer of individual ions from water to acetone + water solvents

1989 ◽  
Vol 67 (8) ◽  
pp. 1268-1273 ◽  
Author(s):  
Mahmoud Mohamad Elsemongy ◽  
Ahmed Ahmed Abdel-Khalek
Keyword(s):  
Glass Electrode ◽  
Aqueous Mixtures ◽  
Free Energies ◽  
Emf Measurements ◽  
Gibbs Energies ◽  
Electrode Potentials ◽  
Gibbs Energies Of Transfer ◽  
Acetone Water ◽  
Alkali Metal Halides ◽  
Dipolar Aprotic Solvents

The standard absolute potentials of hydrogen, Ag–AgX (X = Cl, Br, and I) and M/M+ (M = Li, Na, K, Rb, and Cs) electrodes in nine different acetone + water solvents containing up to 80 wt. % acetone were determined from the emf data at 25 °C of the cells: glass electrode/HCl (m), solvent/AgCl–Ag and glass electrode (M)/MX (m), solvent/AgX–Ag. The standard Gibbs free energies of a transfer of halogen acids and alkali metal halides as well as their constituent individual ions from water to the respective solvents were computed. The observed increases in [Formula: see text] values of all ions with increasing acetone content of the solvent and their relative order in each solvent were interpreted and discussed. A comparison of the present results with those obtained earlier in the dimethyl sulphoxide (DMSO) + water solvents shows the different nature of the two dipolar aprotic solvents, acetone and DMSO, in their aqueous mixtures. Keywords: acetone + water solvents, electrode potentials, emf measurements, individual ions, transfer free energies.

Free energies and entropies of transfer of hydrogen halides from water to aqueous 2-methoxy ethanol and structuredness of the solvents

1985 ◽  
Vol 63 (4) ◽  
pp. 798-803 ◽  
Author(s):  
Prabir K. Guha ◽  
Kiron K. Kundu
Keyword(s):  
Dielectric Constant ◽  
Mixed Solvents ◽  
Three Dimensional ◽  
Halide Ions ◽  
Aqueous Mixtures ◽  
Free Energies ◽  
Hydrogen Halides ◽  
Emf Measurements ◽  
Composition Profiles ◽  
The Individual

Standard free energies (ΔGt0) and entropies (ΔSt0) of transfer of HBr and HI from water to some aqueous solutions of 2-methoxy ethanol (ME) have been determined from emf measurements of the cells: Pt, H2 (g, 1 atm)/HBr (m), solvent/AgBr–Ag and Pt, H2 (g, 1 atm)/KOH (m1), KI (m2), solvent/AgI–Ag, respectively, at seven equidistant temperatures ranging from 15 to 45 °C. ΔGt0 values of HBr and HI as well as of HCl obtained from literature, and particularly that of the individual ions obtained by tetraphenylarsonium tetraphenylboron (TATB) assumption, suggest that while H+ is increasingly stabilized by cosolvent-induced larger "basicity", halide ions (X−) are increasingly destabilized by cosolvent-induced decreased "acidity" and the dielectric constant of the mixed solvents compared to that of water. Analysis of the variation of the observed TΔSt0(HX) and particularly of ΔY (= TΔSt0(H+) + TΔS0t.ch (X−), with composition, in the light of Kundu etal's semi-quantitative theory reveals that ME induces breakdown of three dimensional (3D) tetrahedral structures of water at water-rich compositions. This is being followed by an ordered region due to possible H-bonded cosolvent–water complexation and then the usual disordered region due to packing imbalance. Comparison of ΔY(HI)–composition profiles for aqueous mixtures of t-butanol (ButOH), ethylene glycol (EG), and 1,2-dimethoxy ethane (DME) also demonstrates that the remarkable enhancement of 3D water structures by the well known structure promoter ButOH gets succintly diminished when cosolvent ButOH is replaced by EG, ME, and DME, as is expected from structural and electronic considerations of the cosolvents.

Transfer free energies of alkali metal chlorides and of some individual ions in glycerol and water mixtures

1980 ◽  
Vol 58 (1) ◽  
pp. 79-85 ◽  
Author(s):  
Indra N. Basumullick ◽  
Kiron K. Kundu
Keyword(s):  
Alkali Metal ◽  
Aqueous Mixtures ◽  
Free Energies ◽  
Dispersion Interactions ◽  
Native Conformation ◽  
Alkali Metal Chlorides ◽  
Metal Chlorides ◽  
Emf Measurements ◽  
Reference Electrolyte ◽  
Electrolyte Ph

Staqndard free energies of transfer, ΔGt0, of alkali metal chlorides from water to aqueous mixtures of 10, 30, 50, and 70 wt.% glycerol have been determined from emf measurements of the double cell comprising Ag– AgCl and K(Hg) electrodes at 25°C. These values were divided into individual ion contributions by use of tetraphenyl arsonium tetraphenyl boride (Ph4AsBPh4) assumption, the required ΔGt0 values of the reference electrolyte (Ph4AsPh4B), obtained by measuring solubilities of KBPh4, Ph4AsPi, and KPi (Pi = picrate) in the solvents. The solvation behaviour of the involved ions, as dictated by their respective ΔGt0(i) values, in this as well as in systems of other similar co-solvents like ethanol, ethylene glycol, and urea, suggests that it is determined by one or several effects of acid-base, Born-type, and dispersion interactions. Moreover, comparable stability of PH4B–, particularly in aqueous glycerol and urea, suggests that "specific interactions" are possibly responsible for the well_known folding-unfolding phenomenon of native conformation of proteins in presence of co-solvents.

Solute–solvent effects in the dissociation of thymolsulfonephthalein (an uncharged acid) in aqueous mixtures of acetonitrile (ACN), urea, and dimethyl sulfoxide (DMSO)

1986 ◽  
Vol 64 (8) ◽  
pp. 1521-1526 ◽  
Author(s):  
A. L. De ◽  
A. K. Atta
Keyword(s):  
Solvent Effect ◽  
Dimethyl Sulfoxide ◽  
Solvent Effects ◽  
Mixed Solvent ◽  
Dissociation Constants ◽  
Aqueous Mixtures ◽  
Solvent Interactions ◽  
Gibbs Energies ◽  
Gibbs Energies Of Transfer ◽  
Solvent Systems

The thermodynamic first dissociation constants, [Formula: see text] of thymolsulfonephthalein (H2A), an uncharged acid, have been determined at 25 °C in aqueous mixtures of 10, 30, 50, 70, and 80 wt% acetonitrile (ACN), 11.52, 20.31, 29.64, and 36.83 wt% urea, 20, 40, 60, and 80 wt% dimethyl sulfoxide (DMSO) by spectrophotometric measurements. The solvent effect represented by ∂(ΔG0) = 2.303RT[p(sK)N − p(wK)N] is found to increase in ACN + H2O system as mol% ACN increases in the solvent. In contrast, the corresponding values in urea + H2O as well as DMSO + H2O solvent systems decrease with increase in proportion of organic component in the solvent, the decrease being sharp in urea + H2O. The results have been discussed in terms of the standard Gibbs energies of transfer of H+ from water to the mixed solvent, [Formula: see text] and the relative values of the standard Gibbs energies of transfer of HA−, [Formula: see text] and of [Formula: see text] in all the solvent systems. The overall dissociation behaviour of the acid (H2A) is found to be dictated by the specific solute-solvent interactions of the species participating in the dissociation equilibria.

Activity coefficients and standard Gibbs free energies of transfer of NaCl and KCl from water to aqueous solution of 2-butoxyethanol by EMF studies

1993 ◽  
Vol 71 (12) ◽  
pp. 2038-2042 ◽  
Author(s):  
Yvonne MacPherson ◽  
R. Palepu
Keyword(s):  
Activity Coefficients ◽  
Empirical Equation ◽  
Glass Electrode ◽  
Free Energies ◽  
Selective Electrode ◽  
Cell Potential ◽  
Emf Measurements ◽  
Free Energies Of Transfer ◽  
The Mean ◽  
Mean Activity Coefficients

From the emf measurements of the cell Na- or K-glass electrode|2-butoxyethanol, H2O, NaCl or KCl|Cl ion-selective electrode, the standard potentials were determined at 298 K for five different compositions of the solvent. From the emf data the mean activity coefficients of NaCl and KCl were calculated and fitted to an empirical equation. The standard Gibbs free energies of transfer of NaCl and KCl from water to mixtures of water and 2-butoxyethanol were calculated from the cell potential.

Spectrophotometric study of the dissociation of p-nitroanilinium ion in a binary aqueous-dipolar aprotic solvent system (H2O + acetonitrile) at 25 °C: effect of the solvent

1984 ◽  
Vol 62 (9) ◽  
pp. 1776-1779
Author(s):  
A. L. De ◽  
T. K. De
Keyword(s):  
Solvent Effect ◽  
Dissociation Constants ◽  
Spectrophotometric Study ◽  
Solvent System ◽  
Individual Species ◽  
Aqueous Mixtures ◽  
Gibbs Energies ◽  
Gibbs Energies Of Transfer ◽  
Aqueous Mixture ◽  
The Individual

Thermodynamic dissociation constants (SK) of p-nitroanilinium ion (BH+) have been determined at 25 °C in aqueous solutions containing 20, 40, 60, and 80 wt% acetonitrile (ACN) by spectrophotometric measurements. Standard Gibbs energies of transfer, [Formula: see text] (B) of p-nitroaniline (B) from water to other solvents have been evaluated from the measurement of solubilities at 25 °C. Solvent effect on the dissociation of the acid (BH+), δ(ΔG0) = 2.303RT[p(sK) − p(wK], results in a characteristic minimum with a change in the solvent composition. The result in this protic – dipolar aprotic mixture (H2O + ACN) has been compared with that in aqueous mixture of protic solvent (H2O + ethylene glycol) available from literature. The solvent effect has been discussed in terms of the standard Gibbs energies of transfer [Formula: see text], from water to aqueous mixtures of organic co-solvent of the uncharged base (B), the hydrochloride of the base (BHCl), and hydrochloric acid (HCl) and also in terms of the individual species involved in the dissociation process. The results indicate that solvent effect on dissociation is an involved process, guided by the combined effects of various types of solute–solvent interactions of the Brønsted acid and its conjugate base in addition to the relative solvent basicities.

Temperature dependence of activity coefficients and Gibbs energies of transfer of LiBr in acetonitrile, dimethyl sulfoxide, and N,N-dimethylacetamide from EMF measurements

1997 ◽  
Vol 75 (11) ◽  
pp. 1500-1507 ◽  
Author(s):  
J. Barthel ◽  
R. Neueder ◽  
A. Schröder
Keyword(s):  
Dimethyl Sulfoxide ◽  
Activity Coefficients ◽  
Redox Reaction ◽  
Electromotive Force ◽  
Association Constants ◽  
Aprotic Solvents ◽  
Temperature Dependent ◽  
Emf Measurements ◽  
Gibbs Energies ◽  
Gibbs Energies Of Transfer

Electromotive force (EMF) measurements based on the redox reaction[Formula: see text]are reported for solutions of LiBr at concentrations 0.005 < cLiBr/(mol dm−3) < 0.1 in acetonitrile (AN), dimethyl sulfoxide (DMSO), and N.N-dimethylacetamide (DMA) in the temperature range 278.15 < T/K < 308.15. Gibbs energies of transfer and activity coefficients are estimated. The association constants of LiBr in AN, DMSO, and DMA from EMF measurements and the enthalpy of transfer AN → DMSO are compared to those from other methods of determination. Keywords: temperature-dependent EMF measurements, aprotic solvents, LiBr, TlBr(s) | TlxHg(l) electrode, activity coefficients, transfer quantities.

Thermodynamics of autoionization of aqueous tetrahydrofuran and 1,2-dimethoxyethane and the structuredness of solvents

1981 ◽  
Vol 59 (22) ◽  
pp. 3141-3148 ◽  
Author(s):  
Jayati Datta ◽  
Kiron K. Kundu
Keyword(s):  
Free Energy ◽  
Mixed Solvents ◽  
Relative Size ◽  
Water Structure ◽  
Aqueous Mixtures ◽  
Free Energies ◽  
Emf Measurements ◽  
Energy Data ◽  
Size And Shape ◽  
Relative Free Energy

Autoionization constants (Ks) of aqueous mixtures of tetrahydrofuran (THF) and 1,2-dimethoxyethane (DME) containing 10, 30, and 50 wt.% cosolvent in each case have been determined from emf measurements of the cell: Pt, H2 (g, 1 atm)|KOH (m1), KBr (m2), solvent|AgBr, Ag at seven equidistant temperatures ranging from 5 to 35 °C. The standard free energies (ΔG0), entropies (ΔS0), and enthalpies (ΔH0) of autoionization of the solvents were also evaluated from these data. Relative free energy data, δΔG0(≡sΔG0 − wΔG0), for these solvents as well as those for dioxane (D) – water mixtures taken from the literature, when coupled with the previously determined transfer free energies of H+, ΔGt0(H+), yielded ΔGt0(OH−)app (≡ΔGt0(OH−) − ΔGt0(H2O)) values in the mixed solvents. Relative magnitudes of ΔGt0(H+) and ΔGt0(OH−)app and their non-Born parts, ΔGt,ch0(H+) and ΔGt,ch0(OH−)app in particular, suggest that the "basicity" of these aqueous cosolvents decreases in the order DME > THF > D and their "acidity" in the reverse order, as expected from structural and electronic consideration of these cosolvent molecules. Analysis of the relative entropie contributions, Tδ (ΔS0) (≡T (sΔS0 − wΔS0), for the autoionization of these aqueous cosolvents and in particular ΔSt0(H2O) values derived there from, suggests that while THF promotes three dimenstional (3D) ice-like water structures at initial compositions and D induces breakdown of the 3D structures right from the beginning, DME breaks down water structures at initial compositions, but induces some order around 4–14 mol% DME by forming the possible H-bonded bidentate DME–water complexes. And beyond certain compositions, depending upon the relative size and shape, all the cosolvents break down water structure due to packing imbalance.

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