Showing papers on "Standard molar entropy published in 1986"
TL;DR: In this paper, a solution calorimetry of MgAl2O4-Al8/3O4 solid solutions was performed in a molten 2PbO · B2O3 solvent at 975 K.
Abstract: Solution calorimetry of MgAl2O4-Al8/3O4 solid solutions was performed in a molten 2PbO · B2O3 solvent at 975 K. The results indicate small negative heats of mixing, relative to spinel standard states for both end-members. These data were combined with information on the energetics of the α-γ transition in Al2O3 and on the MgAl2O4-Al8/3O4 (MgO-Al2O3) subsolidus phase relations to estimate the partial molar entropy of mixing of γ-Al8/3O4 in the solid solution. This entropy is much less positive than that calculated from several models for the configurational entropy of mixing of magnesium, aluminum, and vacancies on octahedral and/or tetrahedral sites. The data suggest a good deal of local order to be present in the solid solutions, consistent with negative enthalpies of mixing and entropies of mixing far less than ideal configurational values.
102 citations
TL;DR: In this paper, a pure, crystalline, fine particulate calcium zincate was prepared and its chemical composition was established by chemical analysis, weight loss in thermogravimetric analysis, and by x-ray powder diffraction pattern.
Abstract: Pure, crystalline, fine particulate calcium zincate was prepared. Its chemical composition, was established by chemical analysis, weight loss in thermogravimetric analysis, and by x‐ray powder diffraction pattern. Its solubility in different solutions at 298 K was determined. The solubility data were used to determine the activities of and with respect to pure solid and liquid water, respectively, in calcium zincate. They were also used to determine the vapor pressure of water over calcium zincate and other thermodynamics properties of this system. The equilibrium constant of the reaction was found to be . The standard free energy of formation of calcium zincate was found to be at 298 K. The standard heat of formation was found to be −665 cal/mol, and the standard entropy of formation was found to be 3.35 cal/deg/mol.
44 citations
TL;DR: In this article, the standard Gibbs free energy and enthalpy of formation as well as the standard entropy were determined for sodium zirconate by means of an electrochemical-formation cell in the temperature range 600 to 1100 K.
32 citations
25 citations
TL;DR: In this article, a single phase region was identified for Li x V 6 O 13 between x = 0 and x =0.17 at 120°C, and the lithium chemical diffusion coefficient, self-diffusion coefficient, ionic conductivity and partial molar entropy have been estimated at intervals over this composition range in two specific crystallographic directions.
24 citations
TL;DR: The heat capacity of 4,4′-difluorobiphenyl has been measured by adiabatic calorimetry between 3 and 300 K.
20 citations
TL;DR: In this article, the most reliable values of standard entropy for 10 compounds, the entropies for 40 compounds of non-transition metals, rare-earth metals and actinides have been evaluated by the method of comparative calculation.
Abstract: Using as initial data the most reliable values of standard entropy for 10 compounds, the entropies for 40 compounds of non-transition metals, rare-earth metals and actinides have been evaluated by the method of comparative calculation. Taking into account the features of boride structures, two methods, i.e. additive and proportional, have been selected for the entropy calculations. For the range of borides the entropies were calculated from the linear relation of the latter to the number of boron atoms in the boride. For borides of rare-earth metals allowance has been made for magnetic contributions in conformity with the multiplicity of the corresponding ions. Insignificant differences in the electronic contributions to the entropy for borides and metals have been neglected. For dodecaborides only the additive method has been used. This is specified by the most rigid network that provides the same contribution to compound entropy.
19 citations
TL;DR: In this paper, the vapour pressures and densities of a binary liquid mixture were measured at 182.33 K (the triple point temperature of dinitrogen oxide), and the excess molar enthalpy H m E was determined calorimetrically at about the same temperature (182.3 K).
18 citations
TL;DR: In this paper, a thermodynamic framework has been developed to evaluate the efficiencies of alkaline battery systems for electrolyte (MOH) concentrations from 1 to 8, and the voltage efficiencies were found to be between 90 and 100%.
18 citations
TL;DR: In this paper, the standard molar ideal gas thermodynamic functions of the singly and doubly charged uranyl, neptunyl, plutonyl and americyl ions MOn+2(n= 1 or 2) have been calculated from structural, and electronic and vibrational spectroscopic data.
Abstract: The standard molar ideal gas thermodynamic functions of the singly and doubly charged uranyl, neptunyl, plutonyl and americyl ions MOn+2(n= 1 or 2) have been calculated from structural, and electronic and vibrational spectroscopic data. Estimates have been made for values not found in the literature. The heat capacity, entropy, enthalpy and Gibbs free energy are reported over the temperature range 100–1000 K. The values for 298.15 K have been combined with the standard partial molar entropies of these ions in aqueous solutions to yield the standard molar entropies of hydration. For the hexavalent uranyl ion data are also available for the standard partial molar heat capacity of the aqueous ion and the standard molar heat of formation of the gaseous ion, so that the corresponding quantities of hydration could be calculated. The thermodynamic functions of hydration are interpreted in terms of a model for the hydrated ions.
14 citations
TL;DR: In this paper, low-temperature adiabatic calorimetry was used to determine the molar heat capacity and other thermodynamic properties of KHSO 5 (cr).
TL;DR: In this article, the standard molar entropy of tetraphenylarsonium tetrahenylborate was determined from calorimetric data where available and statistically from published spectroscopic and structural data.
Abstract: Tetraphenylarsonium tetraphenylborate, widely used as a reference electrolyte, is often related to neutral compounds isostructural with its constituent ions. Thermodynamic information concerning them is lacking. Standard molar entropies of the gaseous ions Ph4B–, Ph4P+, and Ph4As+, the species Ph4C, Ph4Si, Ph4Ge, Ph4Sn and Ph4Pb, and the related compounds Ph3CH and Ph2CH2 have been determined from calorimetric data where available and statistically from published spectroscopic and structural data. The latter calculation, deemed more reliable by us, gave the values (in J K–1mol–1): 654, 649 and 648 for the ions, 639, 661, 664, 680 and 694 for the neutral Ph4M compounds, and 541 and 436 for the tri-and di-phenylmethanes. The standard partial molar entropy of the Ph4B– anion is 348 J K–1mol–1, hence its entropy of hydration is —306 J K–1mol–1. This value and the presumed similar one for Ph4As+ indicate that these ions enhance the structure of water. The standard partial molar heat capacities of aqueous Ph4P+, Ph4As+ and Ph4B– are 1231, 1258 and 1051 J K–1mol–1, and those of the gaseous ions are 370, 372 and 367 J K–1mol–1, respectively. The heat-capacity changes on hydration also indicate these ions to be water-structure-makers.
TL;DR: A thermodynamic study of the reaction 3 2 SiF 4 + 1 2 SiO 2 (s) = Si 2 OF 6 (g) in the temperature range 723 to 1288 K was carried out by mass spectrometry.
TL;DR: In this article, the thermoelectric power of a cell with complex formation between Hg2+ and ethylenediamine tetraacetic acid has been measured as a function of pH, concentration of metal, and concentration of ligand, in an aqueous solution with.
Abstract: The thermoelectric power of a cell with complex formation between Hg2+ and ethylenediamine tetraacetic acid has been measured as a function of pH, concentration of metal, and concentration of ligand, in an aqueous solution with . The main experimental results confirm the following theoretical prediction: The entropy change by complex formation, and especially the variation in this change with temperature, may define optimum criteria for converting thermal energy to electric energy. The theory is based on irreversible thermodynamics. New thermodynamic data has been obtained as a secondary result: The apparent complexation constant for formation of HgEDTA2−in this environment at 25°C is determined to be 106.9 at and 108.0 at . The standard entropy and enthalpy change of the complexation is estimated to be, respectively, and at and and at .
TL;DR: In this paper, the vapor pressure of vanadium-oxygen solid solution (0.001−O/V≦0.145) was measured by mass-spectrometric method in the temperature range of 1,855−2,117K.
Abstract: The vapor pressures over vanadium-oxygen solid solution (0.001≦O/V≦0.145) were measured by mass-spectrometric method in the temperature range of 1,855–2,117K. The main vapor species were observed to be V(g) and VO(g). The vapor pressure of V(g) is higher than that of VO(g) over the solid solutions with all O/V ratios except for O/V=0.145. The vapor pressure of V(g) is nearly independent of O/V ratio. The vapor pressure of VO(g) decreases with decreasing O/V ratio. The oxygen partial pressure was calculated as a function of temperature and O/V ratio from the vapor pressures of V(g) and VO(g), from which the partial molar enthalpy and entropy of oxygen in the solid solution were determined. The partial molar enthalpy of oxygen was observed to be independent of composition, suggesting the presence of very weak interaction between interstitial oxygens. The compositional dependence of the partial molar entropy of oxygen can be explained by assuming the occupation of the octahedral site in bcc vanadium lattice ...
TL;DR: In this article, surface-tension measurements were used to investigate the surface adsorption and micellisation of a polystyrene-b-polyisoprene block copolymer in n-hexadecane which is a selectively bad solvent for poly styrene.
Abstract: Surface-tension measurements were used to investigate the surface adsorption and micellisation of a polystyrene-b-polyisoprene block copolymer in n-hexadecane which is a selectively bad solvent for polystyrene. Measurements were made over a range of concentrations (1.29–2.88)x10−4 mol dm−3 and temperatures 25–40°C. The block copolymer was found to be positively adsorbed at the n-hexadecane/air interface. The linearity of plots of γ against In c just below the critical micelle concentration (c.m.c.) indicated an approximately constant surface concentration. The area per block copolymer molecule at the surface had an average value of 4.1 nm2. A plot of In (c.m.c.) against T−1 gave a value for the standard enthalpy of micellisation of -41.9.3.0 kJ per mole of copolymer chains. The standard entropy contribution (-TΔSΔ) to the standard free energy of micellisation was found to be 19.7.3.0 kJ mol−1. These thermodynamic values are in good agreement with results obtained earlier for this system by light scattering and calorimetry.
TL;DR: In this paper, the formation of new paramagnetic complexes is evidenced by the ESR spectra of anion radicals of duroquinone, p-benzoquinone and 2,5-di-t-butyl-p-benzosin tetrahydrofuran, which are recorded in the presence of their parent molecules and cryptand 222 or 18-crown-6.
Abstract: The formation of new paramagnetic complexes is evidenced by the ESR spectra of anion radicals of duroquinone, p-benzoquinone, and 2,5-di-t-butyl-p-benzoquinone in tetrahydrofuran, which are recorded in the presence of their parent molecules and cryptand 222 or 18-crown-6. The numerical values for the equilibrium constant, standard enthalpy and standard entropy of the complex formation are also determined.
TL;DR: The sorption of 5-fluorouracil from aqueous solutions onto poly(methyl methacrylate) was investigated and no crystallinity of the nanoparticles after sorption was detectable by X-ray analysis indicating a partitioning of the drug into the polymer particles-forming a solid solution.
Abstract: The sorption of 5-fluorouracil from aqueous solutions onto poly(methyl methacrylate) was investigated. Linear sorption isotherms were obtained and no crystallinity of the nanoparticles after sorption was detectable by X-ray analysis indicating a partitioning of the drug into the polymer particles forming a solid solution. Standard enthalpy, standard entropy and standard free energy of sorption were -36.9 kJ mol−1 -85.0 J mol−1 K−1 and -12.0 kJ mol−1, respectively.
TL;DR: In this paper, various mathematical-statistical models (analysis of variance, principle components analysis and a hybrid model) are applied to 322 data on the standard entropy of solution of 15 gases in 40 solvents, and 464 data on 20 gases in 45 sol Vents.
TL;DR: In this article, a close correlation has been found for 60 aqueous ions between the standard entropy of hydration Δ S h 0 (ion) and the square of the ionic Stokes radius r s (ion).
Abstract: A close correlation has been found for 60 aqueous ions between the standard entropy of hydration Δ S h 0 (ion) and the square of the ionic Stokes radius r s (ion). Above all, the following relation holds for 37 ions; Δ S h 0 /4π r s 2 N =Δ S cw 0 /4π r ew 2 N =- 3.44×10 -8 J K -1 cm -2 at 298 K. Here N is the Avogadro constant, r ew twice the Stokes radius of water, and Δ S cw 0 the standard entropy of condensation of water vapor at 298 K. This relation is extended to other 23 ions by introducing an effective ionic radius r e (ion) in place of r s (ion) to conserve the relationship mentioned above. In general, there is the relation of r e (ion)= r s (ion)+δ r s with δ r s ≥0, to show an expansion δ r s of ionic Stokes spheres due to the participation of loosely hydrated water in the equilibrium static state of Δ S h 0 (ion).
TL;DR: In this article, the partial molar entropy of atoms physisorbed in registry with solid surfaces is calculated at the critical point of condensation as a function of the lattice incompatibility α between the adsorbate and the surface by the use of the three-dimensional registered cell model.
TL;DR: This chapter illustrates the types of calorimetric data that are obtained with various types of aqueous systems of biological interest, including biomolecules, solute–solvent interactions, and heat capacity data.
Abstract: Publisher Summary This chapter illustrates the types of calorimetric data that are obtained with various types of aqueous systems of biological interest The calorimetric studies involving biomolecules determines the standard enthalpy and heat capacity change, ∆ H° and Δ C ° P , accompanying some chemical or physical chemical process The enthalpy change is combined with the appropriate standard free energy change, ∆ G° , to obtain the change in standard entropy, ∆ S °, at a given temperature, T, from the second law of thermodynamics A common protocol followed when investigating the interactions of biomolecules with water by solution calorimetry involves systematic changes of the temperature, solvent composition, or structure of the molecules themselves The interpretation of the results relies on the use of reference and model compounds because of the complexity of macromolecular systems Heat capacity data seem to be the least complex of the thermodynamic parameters that reflect solute–solvent interactions and can be measured by calorimetry The heat of solution of solid substances, such as amino acid in water, can be measured directly by using a batch calorimeter A flow calorimeter that is used to determine the heats of solution for gaseous hydrocarbons in water is also described in the chapter