共查询到20条相似文献,搜索用时 46 毫秒
1.
Lyubomir Vlaev Mariana Tavlieva Marija Bešter-Rogač 《Journal of solution chemistry》2007,36(2):171-192
On the basis of conductivity studies, empirical equations describing the temperature and concentration dependences of the
electrical conductance of SeO2 solutions in ordinary and heavy water were derived. Values of the equivalent conductivity of ions at infinite dilution, the
first dissociation constant of selenous acid in the temperature region 12 to 45∘C and the thermodynamic parameters of the dissociation process were determined. Using these values, the absolute mobility,
the transport numbers of the ions and their diffusion coefficients were calculated. Furthermore, the values of the transition
energies Δ E
tr.
o for the ions were calculated at different temperatures. The dependencies observed were interpreted using Samoylov’s theory
for positive/negative hydration of the ions. It was shown that the HSeO3
− and DSeO3
− ions were positively hydrated and stabilized the solvent structure, but these effects diminished with an increase of the
temperature. The temperature dependences of the hydration numbers and the effective ionic radii were determined. The values
of the changes of the Gibbs energy, entropy and enthalpy for the transitions of ions from one quasi-equilibrium state to another
were calculated at different temperatures. 相似文献
2.
On the basis of conductometric measurements, empirical equations were derived that describe the temperature and concentration
dependences of the electrical conductance of Na2SeO3 solutions in ordinary and heavy water. The values of the equivalent conductance of the ions at infinite dilution were determined
in the temperature region 12 to 45 °C, as well as the kinetic parameters for ionic motion in the solutions. These parameters
were compared with respect to the solvent nature. The values of the effective ionic radii and ionic hydration numbers were
obtained.
The changes of Gibbs energy, entropy and enthalpy for the transition of ions from one quasi-equilibrium state to another were
calculated at different temperatures. According to the terms of Samoylov’s theory, Na+ and SeO32− ions in H2O and D2O were shown to be positively hydrated and stabilize the solvent structure, with this effect being more pronounced in D2O and increasing slightly with increasing temperature. 相似文献
3.
Ion diffusion kinetics has been studied using the data of conductivity measurements for aqueous solutions of sodium selenite with different concentrations and at different temperatures. Molecular and ionic self-diffusion coefficients have been determined for infinitely dilute solutions in the temperature range 288 K-313 K. The limiting values of ion mobility and changes in the energies of translation of water molecules from ions’ hydration shell have been found. At elevated temperatures, ΔE
tr
0
increases for both ions in direct proportion to the crystallographic radius of the latter. Ion hydration numbers at 298 K have been calculated. The results of this study are interpreted in the light of Samoilov’s theory on positive and negative hydration of ions.Original Russian Text Copyright © 2004 by L. T. Vlaev and S. D. Genieva__________Translated from Zhurnal Strukturnoi Khimii, Vol. 45, No. 5, pp. 870–876, September–October, 2004. 相似文献
4.
The enthalpies of crystallization of LiNO3 and LiNO3–3H2O from aqueous solutions at 25°C, measured by a calorimetric method and determined from the previously published data on the concentration dependence of the enthalpy of solution, are reported. The results are compared with the values obtained from the concentration dependences of the activity coefficients and from the temperature dependences of the solubilities. The enthalpy of solution at infinite dilution and the enthalpy of hydration are given. 相似文献
5.
V. I. Parfenyuk 《Journal of Structural Chemistry》2001,42(6):951-955
The ionic coefficients of the pair interionic interaction in aqueous solutions of 1–1 electrolytes at 298 K were determined from the real activity coefficients of single-charged single ions using the McMillan–Mayer formalism. Analysis of the results of calculations revealed that salt effects are stronger in the case of cations. The weakening of cation hydration (increased negative hydration) and the strengthening of anion hydration (increased positive hydration) enhance the mutual salting of cations and anions. It is shown that the structural effects of hydration produce a strong effect on the interionic interaction in solutions. 相似文献
6.
Eugene Olivier Trevor M. Letcher Paramespri Naidoo Deresh Ramjugernath 《The Journal of chemical thermodynamics》2010,42(1):78-83
Activity coefficients at infinite dilution were determined for 24 solutes (n-alkanes, alk-1-enes, alk-1-ynes, cycloalkanes, alkylbenzenes, and alcohols) in the ionic liquid 1-ethyl-3-methylimidazolium trifluoromethanesulfonate by gas-liquid chromatography at three different temperatures T = (313.15, 323.15, 333.15) K. The partial molar excess enthalpy values at infinite dilution were calculated from the experimental results over the same temperature range. Selectivities and capacities at infinite dilution for the hexane/benzene and methanol/benzene separation problems were calculated from experimental infinite dilution activity coefficient values. The activity coefficients, enthalpies, selectivities, and capacities are discussed and compared to literature values for other ionic liquids, as well as industrial molecular solvents. 相似文献
7.
A. A. Tager A. P. Safronov S. V. Sharina I. Yu. Galaev 《Colloid and polymer science》1993,271(9):868-872
The lower critical solution temperature of aqueous solutions of poly(N-vinyl caprolactam) falls in the 305–307 K range and depends on the molecular weight of the polymer. The thermodynamic functions of mixing at 298 K have been calculated from measurements of vapor pressures and heats of dissolution and dilution. Partial Gibbs energy, partial enthalpy, and partial entropy of mixing were negative over the entire range of composition. Increasing temperature resulted in a decrease in the exothermal character of mixing. Excessive heat capacity values, calculated from the dependencies of enthalpy of mixing on temperature, were positive over the entire composition range. Heat capacity of dilute solutions was measured at 298 K and partial heat capacity of poly(N-vinyl caprolactam) at infinite dilution was shown to be positive. The data obtained point out the hydrophilic and hydrophobic hydration of poly(N-vinyl caprolactam) in aqueous solutions. Hydrophobic hydration dominates at temperatures close to binodal curve. As a result, the mutual mixing of the polymer with water is decreased and phase separation takes place. 相似文献
8.
Summary. The apparent molar volume of lithium, sodium, potassium, and tetramethylammonium cyclohexylsulfamate was determined from the
density data of their aqueous solutions at 293.15, 298.15, 303.15, 313.15, and 323.15 K. The apparent molar expansibility
was calculated from the apparent molar volume at various temperatures. The limiting apparent molar volume and apparent molar
expansibility were evaluated and divided into their ionic components. The partial molar ionic expansibilities were discussed
in terms of the hydration of the ion in solution, as well as in terms of the hydration effects on the solute as a whole. From
the partial molar expansibility of the solute at infinite dilution the partial molar expansibility of the hydration shell
was deduced. The coefficients of thermal expansion of the investigated solutions at 298.15 K were calculated and are presented
graphically. The density of the investigated solutions can be adequately represented by an equation derived by Root. 相似文献
9.
Values of the extraction constants of Zn2+ and Cd2+ from aqueous phosphoric acid solutions (0.36 to 7.31 mol?L?1) by Cyanex 301 in toluene, involving formation of the complexes ZnR2 and CdR2 with R being bis(2,4,4-trimethylpentyl)dithiophosphinate, have been correlated at T=298 K as a function of the ionic strength. For this purpose the activity coefficients of all of the aqueous species have been calculated taking into account both the protolytic equilibria of concentrated phosphoric acid and complexation reactions between the cations and the phosphoric acid species. Good correlations have been obtained for the extraction constant values with the ionic strength, provided the release of water molecules during the extraction processes is considered. Finally, extraction constant values are reported at infinite dilution. 相似文献
10.
The apparent molar volume of lithium, sodium, potassium, and tetramethylammonium cyclohexylsulfamate was determined from the
density data of their aqueous solutions at 293.15, 298.15, 303.15, 313.15, and 323.15 K. The apparent molar expansibility
was calculated from the apparent molar volume at various temperatures. The limiting apparent molar volume and apparent molar
expansibility were evaluated and divided into their ionic components. The partial molar ionic expansibilities were discussed
in terms of the hydration of the ion in solution, as well as in terms of the hydration effects on the solute as a whole. From
the partial molar expansibility of the solute at infinite dilution the partial molar expansibility of the hydration shell
was deduced. The coefficients of thermal expansion of the investigated solutions at 298.15 K were calculated and are presented
graphically. The density of the investigated solutions can be adequately represented by an equation derived by Root. 相似文献
11.
Eugene Olivier Trevor M. Letcher Paramespri Naidoo Deresh Ramjugernath 《The Journal of chemical thermodynamics》2011,43(6):829-833
Activity coefficients at infinite dilution were determined for 27 solutes: n-alkanes, alk-1-enes, alk-1-ynes, cycloalkanes, alkylbenzenes, alcohols, and ketones in the ionic liquid 1-butyl-3-methylimidazolium hexafluoroantimonate, [BMIM][SbF6], by gas–liquid chromatography at three different temperatures, T = (313.15, 323.15, and 333.15) K. The results are compared to published data on related compounds. The partial molar excess enthalpy values at infinite dilution were calculated from the experimental data over the same temperature range. Selectivities and capacities at infinite dilution were calculated for the hexane/benzene and methanol/benzene systems from experimental infinite dilution activity coefficients and compared to the literature values for related ionic liquids, as well as to data on industrial molecular solvents. 相似文献
12.
Relative densities and relative massic heat capacities have been measured for the amino acids β-alanine, 4-aminobutanoic acid, d,l-norleucine and d,l-norvaline in dilute aqueous solution at p = 0.1 MPa and T = (288.15, 298.15, 313.15 and 328.15) K. Apparent molar volumes and apparent molar heat capacities have been calculated and the isothermal concentration dependences of these properties have been modeled to yield apparent molar properties at infinite dilution. Values for apparent molar properties at infinite dilution are compared to those previously reported in the literature. Trends in the temperature dependences of the infinite dilution properties are discussed in terms of methylene group contributions and the variations in these contributions caused by the presence of ionic end groups. 相似文献
13.
The solubility values of pyrazinamide, isoniazid, and p-aminobenzoic acid in buffers (рН 2.0 and 7.4) and octanol were measured in the temperature range of 293.15 to 313.15 K. The dissolution Gibbs energy, enthalpy, and entropy were calculated. The dissolving process was endothermic and enthalpy-determined. The activity coefficients of the compounds at infinite dilution were determined based on the solubility data and thermophysical parameters. A positive deviation from the ideality was observed in all the solutions. A common tendency of the solubility increase with a decrease in the activity coefficients at T = 298.15 K was revealed for the investigated solute-solvent systems. The excess thermodynamic solubility functions were calculated from the temperature dependences of the activity coefficients. The solvation processes were found to have a considerable influence on the solubility of the substances in solutions studied. 相似文献
14.
Clemente Bretti Roberto Di Pietro Paola Cardiano Olivia Gomez-Laserna Anna Irto Gabriele Lando Concetta De Stefano 《Molecules (Basel, Switzerland)》2021,26(23)
The thermodynamics of the interaction of L-glutamic-N,N-diacetic acid (GLDA) with protons was studied potentiometrically at different temperatures, ionic strengths and ionic media. Four protonation constants and corresponding enthalpy changes occurred at infinite dilution together with temperature and ionic strength coefficients. The medium effect was also interpreted in terms of the formation of weak complexes between the ligand and the cations of supporting electrolytes, resulting in a greater tendency of GLDA to chemically interact with Na+ rather than K+ and, in turn, (CH3)4N+. Formation constants of GLDA with Cd2+ were determined in NaCl(aq) at different ionic strength values. Five complex species were found, namely CdL2−, CdHL−, CdH2L0(aq), Cd2L0(aq), and Cd(OH)L3−, whose formation constant values at infinite dilution were log β = 12.68, 17.61, 20.76, 17.52, and 1.77, respectively. All the species results were relevant in the pH range of natural waters, although the Cd2L0(aq) was observed only for CCd ≥ CGLDA and concentrations of >0.1 mmol dm−3. The sequestering ability of GLDA toward Cd2+, evaluated by means of pL0.5, was maximum at pH~10, whereas the presence of a chloride containing a supporting electrolyte exerted a negative effect. Among new generation biodegradable ligands, GLDA was the most efficient in Cd2+ sequestration. 相似文献
15.
A. A. Tager A. P. Safronov E. A. Berezyuk I. Yu. Galaev 《Colloid and polymer science》1994,272(10):1234-1239
Phase diagrams of aqueous solutions of poly(N-vinyl caprolactam) (PVCL), N-vinyl caprolactam copolymer with vinylamine (3.8 mol%) (CP(VCL-VA)), and poly(N-vinyl propylacetamide) (PVPA) were shown to be binodal curves with lower critical solution temperatures (LCST) in the range 304–313.5 K and critical concentrations in the range of 0.02–0.08 polymer weight fraction. Aqueous solutions of N-vinyl caprolactam copolymer with N-vinyl pyrrolidone (80 mol%) (CP(VCL-VP)) remained homogeneous in the entire region of the liquid state of water. The enthalpy of mixing with water of PVPA and CP(VCL-VP) was negative and the curve was concave over the entire range of composition at 298 and 308 K. The excessive heat capacity and partial heat capacity at infinite dilution of PVPA were positive, proving the hydrophobic character of hydration of this polymer. In contrast, these parameters were negative for CP(VCL-VP), revealing hydrophilic hydration. Hydrophilic hydration was predominant in solutions which were homogeneous over a wide temperature range, whereas hydrophobic hydration predominated in solution of polymers with LCST. 相似文献
16.
Coefficients of self-diffusion, absolute speeds of movement of ions and the activation energy of electrical conductivity are found from the conductance measurements of aqueous solutions of selenic acid and sodium selenate at different concentrations in a temperature range of 288–318 K. Both the Stokes and effective radii of ions and their hydrate numbers at 298 K are calculated. The obtained results are interpreted in the frames of Samoilov theory on positive and negative hydration of ions. 相似文献
17.
Guler Ayranci 《The Journal of chemical thermodynamics》2007,39(12):1620-1631
Apparent molar volumes and apparent molar isentropic compressibilities of ascorbic acid (vitamin C) and thiamine hydrochloride (vitamin B1) were determined from accurately measured density and sound velocity data in water and in aqueous NaCl solutions at (283.15, 293.15, 298.15, 303.15, 308.15, and 313.15) K. These volume and compressibility data were extrapolated to zero concentration using suitable empirical or theoretical equations to determine the corresponding infinite dilution values. Apparent molar expansibilities at infinite dilution were determined from slopes of apparent molar volume vs. temperature plots. Ionization of both ascorbic acid and thiamine hydrochloride were suppressed using sufficiently acidic solutions. Apparent molar volumes at infinite dilution for ascorbic acid and thiamine hydrochloride were found to increase with temperature in acidic solutions and in the presence of co-solute, NaCl. Apparent molar expansibility at infinite dilution were found to be constant over the temperature range studied and were all positive, indicating the hydrophilic character of the two vitamins studied in water and in the presence of co-solute, NaCl. Apparent molar isentropic compressibilities of ascorbic acid at infinite dilution were positive in water and in the presence of co-solute, NaCl, at low molalities. Those of thiamine hydrochloride at infinitive dilution were all negative, consistent with its ionic nature. Transfer apparent molar volumes of vitamins at infinite dilution from water solutions to NaCl solutions at various temperatures were determined. The results were interpreted in terms of complex vitamin-water-co-solute (NaCl) interactions. 相似文献
18.
Models having the thermodynamic properties of aqueous alkaline earth halides and NaCl-MgCl2 mixtures
Harold L. Friedman Anne Smitherman Raffaella De Santis 《Journal of solution chemistry》1973,2(1):59-81
A model studied earlier in relation to aqueous 1–1 electrolytes has been applied to the interpretation of the excess free energies of aqueous solutions of the alkaline earth halides up to 1 M ionic strength. Several variations on the model could be fitted to the data. In the one which seems most consistent with the other observations, the cospheres (hydration layers) on the M++ ions were two water molecules thick rather than one as for the alkali metal, tetraalkylammonium, and halide ions. The overlap of cospheres of an M++, M++ pair was found to make a small attractive contribution to the interionic force, while the overlap of cospheres of an M++, X– pair makes a small positive contribution which is almost the same for X–=Cl–, Br–, or I–. Thus, ionic hydration shells which are not penetrated by other ions are not required to account for the observed excess free energies. The model is also fitted to NaCl-MgCl2 mixtures to see whether the new cosphereoverlap parameter which must be determined is consistent with the others. The calculation also shows how the thermodynamic behavior of the mixtures is consistent with the mixture limiting law for unsymmetrical mixtures. The singularities in the mixing coefficients g0 and w0 at infinite dilution dominate their concentration dependence only up to ionic strengths of about 0.01 M in models which fit the data.Most of this report is abstracted from a thesis presented by A. Smitherman to the Graduate School of the State University of New York at Stony Brook in partial fulfillment of the requirements for the M.S. degree, August 1972. 相似文献
19.
The activity coefficients at infinite dilution, gamma13(infinity) for 29 solutes, alkanes, alkenes, alkynes, cycloalkanes, aromatic hydrocarbons, alcohols and water in the ionic liquid 1-ethyl-3-methylimidazolium trifluoroacetate ([EMIM][TFA]), were determined by gas-liquid chromatography at temperatures from 298.15-368.15 K. The partial molar excess enthalpies at infinite dilution DeltaH1(E,infinity) values were calculated from the experimental gamma13(infinity) values obtained over the temperature range. The selectivities for the hexane/benzene and cyclohexane/benzene separation were calculated from gamma13(infinity) and compared to the literature values for other ionic liquids, NMP and sulfolane. 相似文献
20.
Eugene Olivier Trevor M. Letcher Paramespri Naidoo Deresh Ramjugernath 《The Journal of chemical thermodynamics》2010,42(5):646-650
Activity coefficients at infinite dilution were determined for 24 solutes: n-alkanes, alk-1-enes, alk-1-ynes, cycloalkanes, alkylbenzenes and alcohols in the ionic liquid 1-octyl-3-methylimidazolium hexafluorophosphate, [OMIM][PF6], by gas–liquid chromatography at three different temperatures T = (313.15, 323.15, and 333.15) K. The partial molar excess enthalpy values at infinite dilution were calculated from the experimental data over the same temperature range. Capacities and selectivities at infinite dilution for the systems hexane/benzene and methanol/benzene were determined from the experimental data and compared to the literature values for other ionic liquids, as well as for industrial molecular solvents. The influence of the cation and anion of the ionic liquid on the activity coefficient is discussed, as well as the usefulness of [OMIM][PF6] in separating organic liquids. 相似文献