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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, 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.

7 citations

Journal ArticleDOI
TL;DR: In this article, the heat capacities of V3P and V3Si were measured in the temperature range from 150 to 350 K and the authors provided support for a value of 25.6±0.6 J/g
Abstract: The heat capacities of V3P and V3Si were measured in the temperature range from 150–350 K. At 298.15 K, we find Cp(V3P)=22.3±.2 J/g atom K and Cp(V3Si)=22.6±0.2 J/g atom K. At 150 K the heat capacity of V3P is 6% smaller than that of V3Si. Our data provide support for a value of 25.6 J/g atom for the standard entropy of V3Si at 298.15 K, and result in an estimated value of 23.5 J/g atom for the standard entropy of V3P at 298.15 K.

7 citations

Journal ArticleDOI
TL;DR: In this article, a new Dubinin-Astakhov equation based on the extension of the potential theory of adsorption on microporous fractal solids and corresponding thermodynamic functions were formulated and applied for description of the experimental data of adoration on a carbon carbon.
Abstract: A new adsorption isotherm equation based on the extension of the potential theory of adsorption on microporous fractal solids and corresponding thermodynamic functions were formulated and applied for description of the experimental data of adsorption on a microporous carbon. The comparison of the obtained results with the original Dubinin-Astakhov equation is presented. In this paper the dependence of thermodynamic functions (the differential molar enthalpy of adsorption ΔH and the differential molar entropy of adsorption ΔS) on the fractal dimension D are discussed, as well.

7 citations

Journal Article
TL;DR: In this article, the molar entropy and enthalpy of the same one-component system are visualized as functions of temperature by numerical results of a Debye model, and a proper extrapolation does not cause an entropy catastrophe as claimed in Kauzmann's paradox, since the entropy difference between the undercooled melt and the corresponding crystals must be taken into account, and the respective entropies in both states are not connected by an isothermal process.
Abstract: The molar entropy, S, and enthalpy (energy), H, of crystals, glasses and melts of the same one-component systems have been suitably visualized including the transformation from the melt into a glass or crystallization. For the temperature T → 0 K the enthalpy and entropy of the glass are larger by ΔH 0 and ΔS 0 as compared to the stable crystal. The S and H functions of glasses correspond to a simple continuation of these functions from the molten state to lower temperatures. Crystallization occurs as a spontaneous process under production of entropy. Extrapolating the entropy of the molten and crystalline states from the melting range to lower temperatures, which is the basis of Kauzmann's paradox, is ambiguous and misleading, as the extrapolated data deviate considerably from the experimental temperature dependencies of S of glasses and crystals. A proper extrapolation does not cause an entropy catastrophe as claimed in Kauzmann's paradox, since the enthalpy difference between the undercooled melt and the corresponding crystals must be taken into account, and the respective entropies in both states are not connected by an isothermal process. The molar entropy and enthalpy are visualized as functions of temperature by numerical results of a Debye model. The molar entropy is a universal function of the ratio T/T D , wherein T D is the Debye temperature of the well known specific heat capacity, C C . Between 0 K and T D the entropy increases by 1.36 x 3R 4R irrespective of T D . Above T D it increases approximately as 3R × ln(T/T D ). The entropy capacity, C D /T, scales with 1/T D and the enthalpy with T D , both considered as functions of T/T D . The entropy capacity shows a maximum of 2.033 x 3R/T D for T/T D = 0.28.

7 citations

Journal ArticleDOI
TL;DR: In this paper, the heat capacities of N-methylnorephedrine C11H17NO(s) have been measured by a precision automated adiabatic calorimeter over the temperature range from T = 78 K to T = 400 K.
Abstract: This paper reports that low-temperature heat capacities of N-methylnorephedrine C11H17NO(s) have been measured by a precision automated adiabatic calorimeter over the temperature range from T = 78 K to T = 400K. A solid to liquid phase transition of the compound was found in the heat capacity curve in the temperature range of T = 342–364 K. The peak temperature, molar enthalpy and entropy of fusion of the substance were determined. The experimental values of the molar heat capacities in the temperature regions of T = 78–342 K and T = 364–400 K were fitted to two polynomial equations of heat capacities with the reduced temperatures by least squares method. The smoothed molar heat capacities and thermodynamic functions of N-methylnorephedrine C11H17NO(s) relative to the standard reference temperature 298.15 K were calculated based on the fitted polynomials and tabulated with an interval of 5 K. The constant-volume energy of combustion of the compound at T = 298.15K was measured by means of an isoperibol precision oxygen-bomb combustion calorimeter. The standard molar enthalpy of combustion of the sample was calculated. The standard molar enthalpy of formation of the compound was determined from the combustion enthalpy and other auxiliary thermodynamic data through a Hess thermochemical cycle.

7 citations


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Performance
Metrics
No. of papers in the topic in previous years
YearPapers
202316
202229
202141
202055
201949
201857