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Standard molar entropy
About: Standard molar entropy is a research topic. Over the lifetime, 1586 publications have been published within this topic receiving 29886 citations.
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TL;DR: In this paper, a modified Miedema model is employed to calculate the standard enthalpy of formation of titanium hydride (1 ≤ x ≤ 2) using interrelationship among the basic properties of elements Ti and H.
Abstract: A modified Miedema model, using interrelationship among the basic properties of elements Ti and H, is employed to calculate the standard enthalpy of formation of titanium hydride TiHx (1 ≤ x ≤ 2). Based on Debye theories of solid thermal capacity, the vibrational entropy, as well as electronic entropy, is acquired by quantum mechanics and statistic thermodynamics methods, and a new approach is presented to calculate the standard entropy of formation of TiH2. The values of standard enthalpy of formation of TiHx decrease linearly with increase of x. The calculated results of standard enthalpy, entropy, and free energy of formation of TiH2 at 298.16 K are −142.39 kJ/mol, −143.0 J/(molK) and −99.75 kJ/mol, respectively, which is consistent with the previously-reported data obtained by either experimental or theoretical calculation methods. The results show that the thermodynamic model for titanium hydride is reasonable.
13 citations
TL;DR: The 139La NMR data are consistent with the formation of a 1:1 complex resulting from electro static interactions between the sulfonato groups and La(III) as mentioned in this paper.
Abstract: The complexation of La(III) by the water-soluble p-sulfonatocalix[4]arene was thermodynamically characterized by 139La NMR. The 139La NMR data are consistent with the formation of a 1:1 complex resulting from electro static interactions between the sulfonato groups and La(III). The complexation is entropy-driven and is characterized by a positive standard enthalpy (ΔrH° = 11.0 ± 0.5 kJ mol1) and a positive standard entropy (ΔrS° = 108 ± 2 J K1 mol1), which are in very good agreement with the ones determined previously by microcalorimetry. The linear relationship between the 139La NMR linewidth of the free and of the complexed cation, obtained at temperatures ranging from 290 to 340 K, excludes the formation of complexes or aggregates other than the 1:1 complex. It shows also that upon complexation, the effective radius of La(III) undergoes an increase of 50%, related to the replacement of water molecules of the hydrated cation by sulfonato groups of the ligand.Key words: complexation, water-soluble cal...
13 citations
TL;DR: The Gibbs free energy of CaZrO3(o) from monoclinic ZrO2(m) and periclase CaO(p) has been determined as a function of temperature in the range 950-1225 K, using an electrochemical cell incorporating single-crystal CaF2 as the solid electrolyte.
13 citations
TL;DR: In this article, the authors measured the physicochemical properties of 23 hydrophobic ILs at room temperature and determined the thermal expansion coefficient, molecular volume, standard molar entropy and lattice energy for each IL using empirical and semi-empirical equations.
Abstract: BACKGROUND
Ionic liquids (IL) are an interesting solvent choice for specific industrial applications since physicochemical properties can be fine-tuned by modifying the substituent groups or the cation/anion pair. Hydrophobic IL are considered as green solvents and known to be good absorbents for hydrophobic organic compounds. Given their physicochemical properties an industrial application of such compounds can be conceivable. Classical physicochemical properties such as the density, the viscosity and the surface tension have a strong influence on the fluid dynamics, they were therefore measured and determined.
RESULTS
The density, viscosity and surface tension of 23 hydrophobic IL at room temperature were measured. These compounds are potential candidates for the absorption and biodegradation of Volatile Organic Compounds in a two-phase partitioning bioreactor. The thermal expansion coefficient, molecular volume, standard molar entropy and lattice energy were determined for each IL using empirical and semi-empirical equations based on the density values. Viscosity values were correlated by the Arrhenius equation. Then, the surface excess enthalpy and surface excess entropy were determined from the surface tension values.
CONCLUSION
The influence of the presence of different functional moieties (unsaturated bonding, oxygenated and cyanide) and the side chain length in the physicochemical properties of these hydrophobic IL was discussed, since their presence affected directly the density, viscosity and surface tension.
13 citations
TL;DR: In this paper, a gas-formigem Aluminium trichloride is used to transport a gaseous mixture of Yttrium and aluminium in the temperature range of 300°C to 700°C from hot to cold.
Abstract: Yttriumtrichlorid ist mit gasformigem Aluminiumtrichlorid im Temperaturbereich von 300°C bis 700°C von hoherer zu tieferer Temperatur chemisch transportierbar. Aus der Abhangigkeit der Transportrate von der Temperatur und vom Gesamtdruck wird ein Gasphasenkomplex YAl4Cl15,g gefolgert und seine Bildungsenthalpie und Standardentropie hergeleitet.
Chemical Transport of Yttrium Trichloride by Aluminium Trichloride
Yttrium trichloride is transported by gaseous aluminium trichloride in the temperature range of 300°C to 700°C from hot to cold. It is followed a gaseous complex YAl4Cl15,g and the enthalpy of formation as well as the standard entropy of the complex from the dependence of the transport rate on the temperature and the initial pressure of Al2Cl6,g.
13 citations