Showing papers on "Standard molar entropy published in 1981"
TL;DR: In this paper, the authors investigated the thermodynamic properties of the lithium-gallium binary system using electrochemical methods, with special attention being given to the phase of the binary system, including the determination of the composition dependence of the chemical diffusion coefficient, the selfdiffusion coefficient, and the enhancement factor.
Abstract: The thermodynamic properties of the lithium‐gallium binary system have been investigated by the use of electrochemical methods, with special attention being given to the phase . Measurements have also been made of the mass transport parameters in , including the determination of the composition dependence of the chemical diffusion coefficient, the self‐diffusion coefficient, and the enhancement factor. The data on emf vs. composition, obtained by use of the coulometric titration technique at 415°C, show that all three intermediate phases, whose nominal compositions are , , and, have appreciable ranges of stoichiometry. The existence of these three phases was further substantiated by x‐ray diffraction analysis. At 415°C, the constant emf values in the two‐phase regions are 565, 122, 91, and 20 mV with respect to pure liquid lithium, in the order of increasing lithium concentration. Measurements are reported on the temperature dependence of the most gallium‐rich plateau, leading to values of the partial molar entropy and enthalpy of lithium in that two‐phase region. The lithium activity has been found to follow Henry's law in liquid lithium‐gallium alloys and electrochemical measurements of the temperature dependence of the solubility of lithium in liquid gallium confirmed earlier results. The activity of lithium in the vario‐stoichiometric phase lies between and 0.126 at 415°C over a composition range from 44.8 to 56.0 a/o Li. The Gibbs free energy of mixing was determined as a function of composition across the phase and found to have a minimum value of −25.8 kJ/mol at 47.6 a/o Li. The standard Gibbs free energy of formation of all three intermediate phases was evaluated at their nominal stoichiometric compositions; the values are −51, −115, and −62 kJ/mol, respectively. The chemical diffusion coefficient within the phase varies from . On the lithium‐rich side of , the chemical diffusion coefficient increases slightly with increasing lithium concentration. On the lithium‐deficient side of the ideal stoichiometry, the chemical diffusion coefficient increases rapidly as lithium is deleted. After reaching a maximum value at 47.6 a/o Li, it gradually decreases again with further decrease in lithium content. The enhancement factor, which relates the chemical and self‐diffusion coefficients, is also composition dependent. It reaches a maximum value of 56 at the same composition as the peak in the chemical diffusion coefficient and the minimum in the Gibbs free energy of mixing.
86 citations
TL;DR: In this article, a simple method has been proposed to calculate the partial molar entropy for interstitial solid solution with exclusion of nearest neighbor sites, and its accuracy has been tested by comparing its results with exact results known for hard sphere lattice gases.
54 citations
TL;DR: In this paper, the electrical insertion of lithium into cubic and hexagonal tungsten bronzes has been investigated using equilibrium and transient galvanic cell measurements, and the thermodynamic properties (chemical potential and partial molar entropy) of the mixed bronzes have been determined.
33 citations
TL;DR: In this article, the authors measured the heat of reaction and equilibrium pressure for both the oxidation and reduction reactions, (1 7 ) Pr 7 O 12 + ( 1 7 − x 2 ) O 2 = PrO 2−x, by means of a Tian-Calvet-type calorimeter and thermal balance.
21 citations
TL;DR: The study of the concentration dependence and the effect of temperature allowed the determination of the molar extinction change and the dimerization equilibrium constant at four temperatures.
19 citations
TL;DR: In this paper, a temperature oscillation measurement was used to determine the partial molar entropy of Li intercalation in TiS 2 continuously as a function of composition, and the results support earlier suggestions that intercalated Li ions form ordered arrays between TiS2 layers.
Abstract: A novel temperature oscillation measurement was used to determine the partial molar entropy of Li intercalation in TiS 2 continuously as a function of composition. The results support earlier suggestions that intercalated Li ions form ordered arrays between TiS 2 layers. In particular, features in the entropy data are suggestive of ordered arrangements at dilute compositions.
19 citations
TL;DR: In this paper, a series of random β-TiMo alloys ranging from 0-65 atom % Mo via determination of pressure-composition-temperature relationships was investigated; additionally, one ( β- Ti Re alloy ( Ti 37 atom % Re) was investigated.
17 citations
TL;DR: In this article, the surface pressure of mixed monolayers composed of fatty acids and DL-12-hydroxyoctadecanoic acid (12HOA) was measured at various compositions and temperatures.
16 citations
TL;DR: The equilibrium voltage-composition curve for Li x V 6 O 13 between 0 and 0.7 has been determined in a cell using a single crystal V6 O 13 cathode, polymer solid electrolyte and a lithium metal anode as mentioned in this paper.
11 citations
TL;DR: In this paper, low-temperature thermodynamic properties were measured for cyclopropylamine, cyclopentylamine and methylenecyclobutane from 12 K to near their respective boiling temperatures.
7 citations
TL;DR: In this paper, the substituent entropy constants σso for monosubstituted methane and benzene derivatives were determined from the standard entropy of the 3rd law of thermodynamics.
Abstract: Values of the substituent entropy constants σso for monosubstituted methane and benzene derivatives were determined from the standard entropy of the 3rd law of thermodynamics. This parameter is orthogonal to σt or σπ, and seems preferable to π, Es, MR, Mw, Pr and Vw. Two examples of QSAR are successfully analysed in terms of σso.
TL;DR: In this article, the existence of a new phase transition reported earlier by Steinberg et al. is confirmed and its coordinates are traced throughout the interval of concentration from 4.8 to 8.5 mol% Na and for temperatures from 238 to 285K.
Abstract: EMF measurements have been performed on Na-NH3 solution above its well established liquid-liquid critical point. The existence of a new phase transition reported earlier by Steinberg et al. (1980) is confirmed and its coordinates are traced throughout the interval of concentration from 4.8 to 8.5 mol% Na and for temperatures from 238 to 285K. The difference in partial molar entropy of the phases has been estimated to be of the order of the gas constant.
TL;DR: Data is presented for the binding of both tolmetin and salicylic acid to human serum albumin as a function of temperature which make doubtful the validity of using association constants of these drugs to derive thermodynamic constants other than delta G0 values.
Abstract: When drug-protein binding data are evaluated thermodynamically standard free energy (delta G0), standard enthalpy (delta H0) and standard entropy (delta S0) are usually estimated from association constants (Ka) derived from binding data obtained at only two temperatures. Estimation of delta H0 involves the assumption of its constancy in the temperature range studied and linearity of a van't Hoff plot of ln Ka versus 1/T. Sometimes the assumption of such linearity is invalid for theoretical reasons and data obtained at only two temperatures contain no information concerning linearity of this plot. We present data for the binding of both tolmetin and salicylic acid to human serum albumin as a function of temperature which make doubtful the validity of using association constants of these drugs to derive thermodynamic constants other than delta G0 values.
TL;DR: In this article, the standard entropy change ΔS° for the reduction of nonmagnetic, nonconducting oxides, MmOn(s) = mM(s + (n2)O2(g), has been estimated as a function of m, n, and temperature T from motional entropies of oxygen molecules and vibrational entropy of solid phases.
01 Jan 1981
TL;DR: Nayak et al. as mentioned in this paper determined the activities and activity coefficients of Al and Zn in liquid Al-Zn alloys covering the entire composition range in an iso-peribol calorimeter similar to the one used by Oelsen and his associates.
Abstract: The activities and activity coefficients of Al and Zn in liquid Al-Zn alloys covering the entire composition range were determined at 720°C (993° K) in an iso-peribol calorimeter similar to the one used by Oelsen and his associates. The results are in reasonable agreement with the previous values determined by radioactive tracer dew point method, electromotive force measurement method and isopiestic method. The other thermodynamic parameters like the integral molar enthalpy (HM) and its partial quantities, the integral molar entropy (SM) and formation potential (FM/T of Al-Zn alloys were also determined at 720°C (993°K) (Dr. A.K. Nayak, Scientist, National Metallurgical Laboratory)
TL;DR: In this article, an empirical equation was proposed to describe the viscosity B coefficients for dilute solutions of nonelectrolytes in water, which is based on the empirical equation developed for nonaqueous mixtures and an assumption that the entropy change on solution of the liquid solute on the aqueous system in the same way as a change of molar entropy on pure water.
Abstract: An equation is proposed to describe the viscosity B coefficients for dilute solutions of nonelectrolytes in water. It is based on an empirical equation developed for nonaqueous mixtures and an assumption that the entropy change on solution of the liquid solute affects the viscosity of the aqueous system in the same way as a change of molar entropy affects the viscosity of pure water. The equation is shown to represent experimental results well and is especially successful in representing the temperature dependence of the B coefficient for aqueous solutions of alcohols.
TL;DR: In this paper, the vapour pressure of solid and liquid uranium tetrabromide has been measured in the temperature range of 696 to 805 K and 805 to 1003 K respectively by transpiration and evaporation-temperature techniques.