Showing papers on "Standard molar entropy published in 1984"
TL;DR: In this article, the defect structure of perovskite-type oxide solid solution La 1− x Sr x CrO 3− δ was measured as a function of oxygen partial pressure P O 2 at 1000-1300°C, for compositions of x = 0.1-0.3 by means of a thermogravimetric method.
189 citations
TL;DR: In this paper, the standard enthalpy changes of solution measured calorimetrically and those derived from high-precision temperature dependent solubility measurements were compared, and a strong linear correlation between the standard entropy of solution and the number of hydrogens in the hydrocarbon molecule was found.
Abstract: The heats of solution at 25°C for a number of hydrocarbon gases are reported as measured by a calorimetric method. There is excellent agreement between the standard enthalpy changes of solution measured calorimetrically and those derived from high precision temperature dependent solubility measurements. However the calorimetrically determined standard enthalpies of solution of a number of gases are greatly improved over values obtained from low precision temperature dependent solubility measurements. A method is presented to readily estimate the standard errors in the standard enthalpy change for any process derived from the temperature dependence of the equilibrium constant for the process. Comparison of the standard enthalpies and entropies of solution of hydrocarbon gases in water shows that the standard free energies of solution for all hydrocarbon gases investigated are dominated by unfavorable entropy contributions. A strong linear correlation between the standard entropy of solution and the number of hydrogens in the hydrocarbon molecule is found. This correlation suggests that the hydrocarbon hydrophobic effect is regulated by the number of allowable configurations of a water molecule in contact with each C−H group.
87 citations
TL;DR: In this paper, the desorption energy, Ed, and the preexponential factor, ν, for hydrogen from W(100) were determined as a function of coverage, θ, from a series of isobars.
70 citations
TL;DR: In this paper, the relative partial molar free energy, entropy and enthalpy of solution of oxygen in this phase were derived and discussed in relation to the metal vacancy model.
48 citations
TL;DR: In this article, high-temperature drop-calorimetric measurements have been performed on a pure synthetic specimen of tungsten disulfide, WS2, and the following molar thermodynamic quantities are reported at To = 298.15 K: the standard enthalpy of formation, ΔfHmo(To), −(240.8±3.1) kJ·mol−1; the heat capacity, Cp,mo(to), (63.82±0.32) J·K−1·mol −1; and
34 citations
TL;DR: In this paper, the surface tension of octylsulfinylethanol (OSE) was measured as a function of temperature at concentrations around the critical micelle concentration (CMC).
34 citations
TL;DR: In this paper, the thermodynamics of micelle formation by polystyrene-b-polyisoprene block copolymer in N,N′-dimethylacetamide, which is a selectively bad solvent for poly isoprene, has been investigated.
Abstract: The thermodynamics of micelle formation by a polystyrene-b-polyisoprene block copolymer in N,N′-dimethylacetamide, which is a selectively bad solvent for polyisoprene, has been investigated. The micelles have a very narrow size distribution enabling the association process to be treated as a single-stage equilibrium. The temperature dependence of the critical micelle concentration was determined from measurements of scattering intensity against temperature carried out at six concentrations within the range 2.3 × 10−7 to 1.2 × 10−4 mol dm−3. A plot of 1n (c.m.c.) against T−1 gave a value for the standard enthalpy of micellisation (per mole of copolymer chains in the micelle) of − 153 ± 6 kJ mol−1. The standard entropy contribution (-TΔSΘ) to the standard free energy of micellisation was found to be positive. These results are in strong contrast to those reported for synthetic surfactants in aqueous media for which a favourable standard entropy change is the factor mainly responsible for micelle formation.
16 citations
01 Jul 1984
TL;DR: In this paper, the authors presented the values of standard entropy, standard enthalpy of formation, and standard free energy of formation for Cr and its solid and aqueous species, after careful evaluation of the best available current thermochemical data.
Abstract: Values of standard entropy, standard enthalpy of formation, and standard free energy of formation for Cr and its solid and aqueous species are tabulated in this report. These values were selected or recalculated after careful evaluation of the best available current thermochemical data. The basis for selection of data centered on conformation with the recent studies of Vasil'ev et al. (1977a,b, 1978, 1980, 1981) for Cr/sup 3 +/ data and O'Hare and Boerio (1975) for CrO/sub 4//sup 2 -/ data. The thermodynamic data presented in this report will be incorporated into the data base of the geochemical computer model, MINTEQ. The distribution of Cr in the environment among its aqueous inorganic species is, according to the thermodynamic data, highly dependent upon pH and Eh and the presence of complexing ligands. The speciation of Cr in natural waters is also controlled by reduction and complexation by organic matter, adsorption and oxidation by Mn-oxide in suspended particulate matter and sediment, and reduction by H/sub 2/S released from anoxic sediments. 89 references, 8 figures, 11 tables.
16 citations
TL;DR: In this article, the authors compared the features displayed by the differential scanning calorimetric traces with reference to the rate of equilibration of the processes associated to a disperse order model (volume fraction and particle number adjustment, and domain dissolution).
Abstract: Microcalorimetric experiments in pre-annealed and furnace cooled αCu-Al alloys containing 19,13, and 6.5 at. pct aluminum were performed at different heating rates. The features displayed by the differential scanning calorimetric traces were studied with reference to the rate of equilibration of the processes associated to a disperse order model (volume fraction and particle number adjustment, and domain dissolution). Such a comparison indicates that the observed features harmonize quite well with this model. The disordering reactions were found to be first order transitions. Volume fractions and radii of the ordered particles as well as latent and molar heats of dissolution were calculated. The decrease of the critical temperatureT
c
with increasing Al content is explained through a combination of the lattice parameter and the quasichemical effects. The molar entropy of dissolution increases as the alloy becomes more concentrated, indicating that internal order within domains also increases correspondingly.
14 citations
TL;DR: The total pressure vapour-liquid equilibrium measurements, on { x CCl 4 + (1 − x )Cl(CH 2 ) m Cl} (m = 1 to 4), at 303.15 K, by a static method were made as discussed by the authors.
12 citations
TL;DR: In this paper, the lattice molar heat capacities of MoO2 and MoO3 were measured in the range between 350 and 950 K by means of adiabatic scanning calorimetry.
TL;DR: The solution of trace amounts of samarium (0.1 to 10000 ppm) in forsteritic olivine was investigated by electromotive force galvanic cell measurements.
TL;DR: In this paper, the vapour pressures and densities of a binary liquid mixture were measured at 182.32 K (the triple point temperature of dinitrogen oxide) and at a slightly higher temperature (184.03 K).
TL;DR: In this article, a modified coulometric titration method with the electrochemical cell O in liquid InSn alloys, ZrO2 (+ CaO)¦ air, Pt was used to measure the activity coefficient γo of oxygen in liquid Alloys at 1073 and 1273 K over the entire composition range.
Abstract: A modified coulometric titration method with the electrochemical cell O in liquid InSn alloys¦ZrO2 (+ CaO)¦air, Pt was used to measure the activity coefficient γo of oxygen in liquid InSn alloys at 1073 and 1273 K over the entire composition range. The molar enthalpy ΔHO° and the molar entropy ΔSO° of oxygen dissolution for 1 2 O 2 (101325 Pa) → O(1 mol .% ) were evaluated from the results. The In γO values and the ΔHO° and ΔSoO° values plotted in terms of alloy composition lie approximately on the line corresponding to the additive equation.
TL;DR: The heat capacities of cesium and rubidium chromates have been measured by differential scanning calorimetry (DSC) in the temperature range 350-780 K as discussed by the authors.
TL;DR: The heat capacity of potassium hexafluoroferrate(III) has been measured between 12 and 320 K as mentioned in this paper, and the standard molar entropy of K 3 FeF 6 (cr) at 298.15 K has been estimated to be (321 ± 5) J·K −1 ·mol −1.
TL;DR: In this article, the lattice entropy of isostructural iso-anionic rare-earth compounds is estimated by taking into account the effects of cation mass and molar volume.
Abstract: Resolution of excess entropy of many types of transitions and estimation of standard entropy at 298.15K of compounds, for which experimental entropies have not yet been measured, depend on a reliable estimation of the lattice entropy. By taking into account the effects of cation mass and molar volume of the rare-earth compounds, the following formula is proposed
for the estimation of the lattice entropy of isostructural iso-anionic rare-earth compounds. We have investigated 32 compounds, and found good agreements between estimated and experimental entropies.
TL;DR: In this paper, the standard entropy S°298 (g) of the 3rd law of thermodynamics was estimated by regression analysis of log γ of gas-chromatography determined under non-polar conditions on S° 298 (g).
Abstract: Standard entropy S°298 (g) of the 3rd law of thermodynamics can be estimated by the regression analysis of log γ of gas-chromatography determined under non-polar conditions on S°298 (g). Results can be practically achieved by using the concept of the mean-square fluctuating electric field.