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1.
We have measured the densities at temperatures T = (278.15 to 363.15) K and heat capacities at T = (278.15 to 393.15) K of aqueous solutions of 18-crown-6 and of (18-crown-6 + KCl) at molalities m = (0.02 to 0.3) mol · kg−1 and at the pressure 0.35 MPa. We have calculated apparent molar volumes V? and apparent molar heat capacities Cp,? for 18-crown-6(aq), and we have applied Young’s Rule and have accounted for chemical speciation and relaxation effects to resolve V? and Cp,? for the (18-crown-6: K+,Cl)(aq) complex in the mixture. We have also calculated estimates of the change in volume ΔrVm, the change in heat capacity ΔrCp,m, the change in enthalpy ΔrHm, and the equilibrium quotient log Q for formation of the complex at T = (278.15 to 393.15) K and m = (0 to 0.3) mol · kg−1.  相似文献   

2.
The (p, ρ, T) properties of pure methanol, the (p, ρ, T) properties and apparent molar volumes V? of ZnBr2 in methanol at T = (298.15 to 398.15) K and pressures up to p = 40 MPa are reported, and apparent molar volumes have been evaluated. The experimental (p, ρ, T, m) values were described by an equation of state. For the solutions the experiments were carried out at molalities m = (0.05772, 0.37852, 0.71585 and 1.95061) mol · kg−1 of zinc bromide.  相似文献   

3.
We determined apparent molar volumes V? at 278.15 ? (T/K) ? 368.15 and apparent molar heat capacities Cp,? at 278.15 ? (T/K) ? 393.15 at p = 0.35 MPa for aqueous solutions of tetrahydrofuran at m from (0.016 to 2.5) mol · kg?1, dimethyl sulfoxide at m from (0.02 to 3.0) mol · kg?1, 1,4-dioxane at m from (0.015 to 2.0) mol · kg?1, and 1,2-dimethoxyethane at m from (0.01 to 2.0) mol · kg?1. Values of V? were determined from densities measured with a vibrating-tube densimeter, and values of Cp,? were determined with a twin fixed-cell, differential, temperature-scanning calorimeter. Empirical functions of m and T for each compound were fitted to our V? and Cp,? results.  相似文献   

4.
We determined apparent molar volumes V? at 298.15 ? (T/K) ? 368.15 and apparent molar heat capacities Cp,? at 298.15 ? (T/K) ? 393.15 for aqueous solutions of HIO3 at molalities m from (0.015 to 1.0) mol · kg?1, and of aqueous KIO3 at molalities m from (0.01 to 0.2) mol · kg?1 at p = 0.35 MPa. We also determined V? at the same p and at 298.15 ? (T/K) ? 368.15 for aqueous solutions of KI at m from (0.015 to 7.5) mol · kg?1. We determined Cp,? at the same p and at 298.15 ? (T/K) ? 393.15 for aqueous solutions of KI at m from (0.015 to 5.5) mol · kg?1, and for aqueous solutions of NaIO3 at m from (0.02 to 0.15) mol · kg?1. Values of V? were determined from densities measured with a vibrating-tube densimeter, and values of Cp,? were determined with a twin fixed-cell, differential temperature-scanning calorimeter. Empirical functions of m and T were fitted to our results for each compound. Values of Ka, ΔrHm, and ΔrCp,m for the proton ionization reaction of aqueous HIO3 are calculated and discussed.  相似文献   

5.
Apparent molar volumes Vφ and apparent molar heat capacities Cp,φ were determined for aqueous solutions of l-proline, l-proline with equimolal HCl, and l-proline with equimolal NaOH at the pressure p=0.35 MPa. Density measurements obtained with a vibrating-tube densimeter at temperatures (278.15⩽T/K⩽368.15) were used to calculate Vφ values, and heat capacity measurements obtained with a twin fixed-cell, differential-output, power-compensation, temperature-scanning calorimeter at temperatures (278.15⩽T/K⩽393.15) were used to calculate Cp,φ values. Speciation arising from equilibrium was accounted for using Young’s Rule, and semi-empirical equations describing (Vφ, m, T) and (Cp,φ, m, T) for each aqueous equilibrium species were fitted by regression to the experimental results. From these equations, the volume change ΔrVm and heat capacity change ΔrCp,m for the protonation and deprotonation reactions were calculated. Additionally, the ΔrCp,m expression was integrated symbolically to yield values of the reaction enthalpy change ΔrHm, reaction entropy change ΔrSm, and equilibrium molality reaction quotient Q for both reactions. The results provide a much-improved thermodynamic characterization of aqueous l-proline and of its protonation and deprotonation equilibria.  相似文献   

6.
Apparent molar volumes Vϕ and apparent molar heat capacities Cp,ϕ were determined at the pressure 0.35 MPa for aqueous solutions of magnesium nitrate Mg(NO3)2 at molalities m = (0.02 to 1.0) mol · kg−1, strontium nitrate Sr(NO3)2 at m = (0.05 to 3.0) mol · kg−1, and manganese nitrate Mn(NO3)2 at m = (0.01 to 0.5) mol · kg−1. Our Vϕ values were calculated from solution densities obtained at T = (278.15 to 368.15) K using a vibrating-tube densimeter, and our Cp,ϕ values were calculated from solution heat capacities obtained at T = (278.15 to 393.15) K using a twin fixed-cell, differential, temperature-scanning calorimeter. Empirical functions of m and T were fitted to our results, and standard state partial molar volumes and heat capacities were obtained over the ranges of T investigated.  相似文献   

7.
We have measured the densities of aqueous solutions of l-methionine, l-methionine plus equimolal HCl, and l-methionine plus equimolal NaOH at temperatures 278.15  T/K  368.15, at molalities 0.0125  m/mol · kg−1  1.0 as solubilities allowed, and at p = 0.35 MPa using a vibrating tube densimeter. We have also measured the heat capacities of these solutions at 278.15  T/K  393.15 and at the same m and p using a twin fixed-cell differential temperature-scanning calorimeter. We used the densities to calculate apparent molar volumes Vϕ and the heat capacities to calculate apparent molar heat capacities Cp,ϕ for these solutions. We used our results and values from the literature for Vϕ(T, m) and Cp,ϕ(T, m) for HCl(aq), NaOH(aq), and NaCl(aq) and the molar heat capacity change ΔrCp,m(T, m) for ionization of water to calculate parameters for ΔrCp,m(T, m) for the two proton dissociations from protonated aqueous cationic l-methionine. We integrated these results in an iterative algorithm using Young’s Rule to account for the effects of speciation and chemical relaxation on Vϕ(T, m) and Cp,ϕ(T, m). This procedure yielded parameters for Vϕ(T, m) and Cp,ϕ(T, m) for methioninium chloride {H2Met+Cl(aq)} and for sodium methioninate {Na+Met(aq)} which successfully modeled our observed results. Values are given for ΔrCp,m, ΔrHm, pQa, ΔrSm, and ΔrVm for the first and second proton dissociations from protonated aqueous l-methionine as functions of T and m.  相似文献   

8.
The partial molar volumes, , and partial molar heat capacities, , at infinite dilution have been determined for the compounds N-acetylasparaginamide, N-acetylglutaminamide, N-acetyltyrosinamide, and N-acetyllysinamide monohydrochloride in aqueous solution at T = (288.15, 298.15, 313.15, and 328.15) K. These results, along with the literature data for the compound N-acetylglycinamide, have been used to calculate the amino acid side-chain contributions to the thermodynamic properties. These side-chain contributions are compared with those obtained using small peptides as side-chain model compounds.  相似文献   

9.
We have measured the densities of aqueous solutions of glycine, glycine plus equimolal HCl, and glycine plus equimolal NaOH at temperatures 278.15  T/K  368.15, molalities 0.01  m/mol · kg−1  1.0, and at p = 0.35 MPa, using a vibrating tube densimeter. We have also measured the heat capacities of these solutions at 278.15  T/K  393.15 and at the same m and p using a fixed-cell differential scanning calorimeter. We used the densities to calculate apparent molar volumes Vϕ and the heat capacities to calculate apparent molar heat capacities Cp,ϕ for these solutions. We used our results and values of Vϕ(T, m) and Cp,ϕ(T, m) for HCl(aq), NaOH(aq), NaCl(aq) from the literature to calculate parameters for ΔrCp,m(T, m) for the first and second proton dissociations from protonated aqueous cationic glycine. We then integrated this value of ΔrCp,m(T, m) in an iterative algorithm, using Young’s Rule to account for the effects of speciation and chemical relaxation on the observed Vϕ and Cp,ϕ of the solutions. This procedure yielded parameters for Vϕ(T, m) and Cp,ϕ(T, m) for glycinium chloride {H2Gly+Cl(aq)} and sodium glycinate {Na+Gly(aq)} which successfully modeled our observed results. We have then calculated values of ΔrCp,m, ΔrHm, ΔrVm, and pQa for the first and second proton dissociations from protonated aqueous glycine as functions of T and m.  相似文献   

10.
Densities have been measured for Glucose + HCl +Water at 10-degree intervals from 278.15 to 318.15 K. The apparent molar volumes (V Φ,G) and standard partial molar volumes (V Φ,G 0 ) for Glucose in aqueous solution of 0.2, 0.4, 0.7, 1.1, 1.6, 2.1 mol·kg−1 HCl have been calculated as well as volumetric interaction parameters (V EG) for Glucose — HCl in water and standard partial molar expansion coefficients (∂V Φ,G 0 / ∂T)p. Results show that (1) the apparent molar volume for Glucose in aqueous HCl solutions increases lineally with increasing molality of Glucose and HCl; (2) V Φ,G/0 for Glucose in aqueous HCl solutions increases lineally with increasing molality of HCl; (3) the volumetric interaction parameters for Glucose — HCl pair in water are small positive and vary slightly with temperature; (4) the relation between V Φ,G 0 and temperature exists as V Φ,G 0 = a 0 + a 1(T − 273.15 K)2/3; (5) values of (∂V Φ,G 0 / ∂T)p are positive and increase as temperatures rise, and at given temperatures decrease slightly with increasing molalities of HCl, indicating that the hydration of glucose decreases with increasing temperature and molality of HCl. These phenomena are interpreted successfully by the structure interaction model. Translated from Acta Chimica Sinica, 2006, 64(16): 1635–1641 (in Chinese)  相似文献   

11.
Apparent molar heat capacities Cp, φand apparent molar volumesVφ were determined for aqueous solutions of N, N - dimethylformamide andN , N - dimethylacetamide at temperatures from 278.15 to 393.15 K and at the pressure 0.35 MPa. The molalities investigated ranged from 0.015 mol ·kg  1to 1.0 mol · kg  1. We used a vibrating-tube densimeter (DMA 512P, Anton PAAR, Austria) to determine the densities and volumetric properties. Heat capacities were obtained using a twin fixed-cell, power-compensation, differential-output, temperature-scanning calorimeter (NanoDSC 6100, Calorimetry Sciences Corporation, Spanish Fork, UT, U.S.A.). The results were fit by regression to equations that describe the surfaces (Vφ,T , m) and (Cp, φ, T, m). Infinite dilution partial molar volumes V2oand heat capacitiesCp,2o were obtained over the range of temperatures by extrapolation of these surfaces to m =  0.  相似文献   

12.
Apparent molar heat capacities Cp, φand apparent molar volumesVφ were determined for aqueous solutions of 1-butanol, 2-butanol (both R andS isomers), isobutanol (2-methyl-1-propanol), and t -butanol (2-methyl-2-propanol) at temperatures from 278.15 K to 393.15 K and at the pressure 0.35 MPa. The molalities investigated ranged from 0.02 mol · kg  1to 0.5 mol · kg  1. We used a vibrating-tube densimeter (DMA 512P, Anton Paar, Austria) to determine the densities and volumetric properties. Heat capacities were obtained using a twin fixed-cell, power-compensation, differential-output, temperature-scanning calorimeter (NanoDSC 6100, Calorimetry Sciences Corporation, Provo, UT, U.S.A.). The results were fit by regression to equations that describe the surfaces (Vφ, T, m) and (Cp,φ, T, m). Infinite dilution partial molar volumesV2o and heat capacities Cp,2owere obtained over the range of temperatures by extrapolation of these surfaces to m =  0.  相似文献   

13.
We have measured the densities of aqueous solutions of serine, serine plus equimolal HCl, and serine plus equimolal NaOH at temperatures 278.15  T/K  368.15, molalities 0.01  m/mol · kg−1  1.0, and at the pressure p = 0.35 MPa, using a vibrating tube densimeter. We have also measured the heat capacities of these solutions at 278.15  T/K  393.15 and at the same m and p using a fixed-cell differential temperature-scanning calorimeter. We used the densities to calculate apparent molar volumes Vϕ and the heat capacities to calculate apparent molar heat capacities Cp,ϕ for these solutions. We used our results and values from the literature for Vϕ(T,m) and Cp,ϕ(T,m) for HCl(aq), NaOH(aq), and NaCl(aq) and the molar heat capacity change ΔrCp,m(T,m) for ionization of water to calculate ΔrCp,m(T,m) for proton dissociations from protonated aqueous cationic serine and from the zwitterionic form. We integrated these results in an iterative algorithm using Young’s rule to account for the effects of speciation and chemical relaxation on the observed Vϕ(T,m) and Cp,ϕ(T,m) of the solutions. This procedure yielded parameters for Vϕ(T,m) and Cp,ϕ(T,m) for serinium chloride {H2Ser+Cl(aq)} and for sodium serinate {Na+Gly(aq)} which successfully modeled our observed results. We have then calculated ΔrCp,m, ΔrHm, ΔrVm and pQa for the first and second proton dissociations from protonated aqueous serine as functions of T and m.  相似文献   

14.
We have measured the densities of aqueous solutions of alanine, alanine plus equimolal HCl, and alanine plus equimolal NaOH at temperatures 278.15  T/K  368.15, at molalities 0.0075  m/mol · kg−1  1.0, and at the pressure p = 0.35 MPa using a vibrating tube densimeter. We have also measured the heat capacities of these solutions at 278.15  T/K  393.15 and at the same m and p using a twin fixed-cell differential temperature-scanning calorimeter. We used the densities to calculate apparent molar volumes Vϕ and the heat capacities to calculate apparent molar heat capacities Cp,ϕ for these solutions. We used our results and values from the literature for Vϕ(T, m) and Cp,ϕ(T, m) for HCl(aq), NaOH(aq), and NaCl(aq) and the molar heat capacity change ΔrCp,m(T, m) for ionization of water to calculate parameters for ΔrCp,m(T, m) for the two proton dissociations from protonated aqueous cationic alanine. We integrated these results in an iterative algorithm using Young’s Rule to account for the effects of speciation and chemical relaxation on Vϕ(T, m) and Cp,ϕ(T, m). This procedure yielded parameters for Vϕ(T, m) and Cp,ϕ(T, m) for alaninium chloride {H2Ala+Cl(aq)} and for sodium alaninate {Na+Ala(aq)} which successfully modeled our observed results. Values are given for ΔrCp,m, ΔrHm, pQa, ΔrSm, and ΔrVm for the first and second proton dissociations from protonated aqueous alanine as functions of T and m.  相似文献   

15.
We have measured the densities of aqueous solutions of isoleucine, threonine, and equimolal solutions of these two amino acids with HCl and with NaOH at temperatures 278.15  T/K  368.15, at molalities 0.01  m/mol · kg−1  1.0, and at the pressure 0.35 MPa using a vibrating tube densimeter. We have also measured the heat capacities of these solutions at 278.15  T/K  393.15 and at the same m and p using a twin fixed-cell differential temperature-scanning calorimeter. We used the densities to calculate apparent molar volumes Vϕ and the heat capacities to calculate apparent molar heat capacities Cp,ϕ for these solutions. We used our results and values from the literature for Vϕ(T, m) and Cp,ϕ(T, m) for HCl(aq), NaOH(aq), and NaCl(aq) and the molar heat capacity change ΔrCp,m(T, m) for ionization of water to calculate parameters for ΔrCp,m(T, m) for the two proton dissociations from each of the protonated aqueous cationic amino acids. We used Young’s Rule and integrated these results iteratively to account for the effects of equilibrium speciation and chemical relaxation on Vϕ(T, m) and Cp,ϕ(T, m). This procedure gave parameters for Vϕ(T, m) and Cp,ϕ(T, m) for threoninium and isoleucinium chloride and for sodium threoninate and isoleucinate which modeled our observed results within experimental uncertainties. We report values for ΔrCp,m, ΔrHm, pQa, ΔrSm, and ΔrVm for the first and second proton dissociations from protonated aqueous threonine and isoleucine as functions of T and m.  相似文献   

16.
Apparent molar volumes Vφ and apparent molar heat capacities Cp,φ were determined for aqueous solutions of lead nitrate [Pb(NO3)2] at m=(0.02 to 0.5) mol · kg−1, at T=(278.15 to 393.15) K, and at the pressure 0.35 MPa. Our Vφ values were calculated from densities obtained using a vibrating-tube densimeter, and our Cp,φ values were obtained using a twin fixed-cell, power-compensation, differential-output, temperature-scanning calorimeter. Our results were fitted to functions of m and T and compared with results from the literature.  相似文献   

17.
The apparent molar volume of paracetamol (4-acetamidophenol) in water, 0.1 M HCl and 0.154 M NaCl as solvents at (298.15, 303.15, 308.15 and 310.65) K temperatures and at a pressure of 101.325 kPa were determined from the density data obtained with the help of a vibrating-tube Anton Paar DMA-48 densimeter. The partial molar volume, Vm, of paracetamol in these solvents at different temperatures was evaluated by extrapolating the apparent molar volume versus molality plots to m = 0. In addition, the partial molar expansivity, E°, the isobaric coefficient of thermal expansion, αp, and the interaction coefficient, Sv, have also been computed. The expansivity data show dependence of E° values on the structure of the solute molecules.  相似文献   

18.
Apparent molar volumes Vφ and apparent molar heat capacities Cp,φ were determined for aqueous solutions of barium nitrate Ba(NO3)2 at molalities m=(0.0025 to 0.2) mol · kg−1, at T=(278.15 to 393.15) K, and at the pressure 0.35 MPa. Our Vφ values were calculated from densities obtained using a vibrating-tube densimeter, and our Cp,φ values were obtained using a twin fixed-cell, power-compensation, differential-output, temperature-scanning calorimeter. Our results were fitted to functions of m and T and compared with values from the literature.  相似文献   

19.
Apparent molar volumes Vφof aqueous KCl, KOH, and NaOH and apparent molar heat capacities Cp, φof aqueous HCl, KCl, KOH, and NaOH have been determined at the pressure p =  0.35 MPa, and at molalities 0.015 ⩽m / mol · kg  1 0.5. Densities were measured using a vibrating-tube densimeter (DMA 512, Anton Paar, Austria) at temperatures 278.15 ⩽T / K 368.15. These values were used to calculate the apparent molar volumes. A fixed-cell, differential-output, power-compensating, temperature-scanning calorimeter (NanoDSC model 6100, Calorimetry Sciences Corporation, Spanish Fork, UT, U.S.A.) was used to measure the heat capacities of the same solutions at temperatures 278.15 ⩽T / K 393.15. Results were fitted by using equations that describe the surfaces (m, T, Vφ) and (m, T, Cp, φ). Using these equations, we have calculated the surfaces (m, T, ΔrVm), (m, T, ΔrCp, m), (m, T, ΔrHm), (m,T , p Qa), and (m, T,ΔrSm ) for the ionization of water in the presence of combinations of the above electrolytes. The last three surfaces were calculated by integration using our (m,T , ΔrCp, m) surface and literature values for the molality dependence of ΔrHmand pQa at T =  298.15 K.  相似文献   

20.
Accurate excess molar volumes (VE), at ambient pressure and 303.15 K, have been determined in the ternary liquid mixtures of N,N-dimethylformamide (DMF) + 2-pentanone (PE) + 1-alkan-1-ols (C3-C6) and in the binary mixtures of PE + alkan-1-ols (C3-C6) as a function of composition. The alkanols include 1-propanol, 1-butanol, 1-pentanol and 1-hexanol. The intermolecular interactions and structural effects were analyzed on the basis of the measured and derived properties. Excess molar volumes increase in magnitude with increase in chain length of alcohol. Valuable information on the behavior and governing factors of the liquid structure of the strongly associated solvents studied were inferred from the parameters deduced. The VE results were correlated and fitted by the Redlich-Kister equation for binary mixtures and by the Cibulka equation for ternary mixtures, as a function of mole fraction. Several predictive empirical relations were applied to predict the excess volumes of ternary mixtures from the binary mixing data. An analysis of the data indicates a good agreement between experimental results and predicted values in all ternary systems. A discussion is presented and deviations are interpreted in terms of size, shape, the position of ketone group, the chain length of alkanol and hydrogen bond effects in the liquid mixtures studied to explain chemical and thermophysical behavior.  相似文献   

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