scispace - formally typeset
Search or ask a question
Topic

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.


Papers
More filters
Journal ArticleDOI
TL;DR: In this article, the dissolution behavior of naftopidil in methanol, ethanol, ethyl acetate, toluene, acetone, acetonitrile and two mixtures of (ethyl acetate+methanol) and (ethylacetate+ethanol).

56 citations

Journal ArticleDOI
TL;DR: In this paper, a thermodynamic investigation of the Claisen rearrangement of chorismate2-(aq) to prephenate2(aq) has been performed using microcalorimetry and high-performance liquid chromatography.
Abstract: A thermodynamic investigation of the Claisen rearrangement of chorismate2-(aq) to prephenate2-(aq) has been performed using microcalorimetry and high-performance liquid chromatography. The study used a well-characterized monofunctional chorismate mutase from Bacillus subtilis that was devoid of prephenate dehydrogenase and prephenate dehydratase activities. The calorimetric measurements led to a standard molar enthalpy change = −(55.4 ± 2.3) kJ mol-1 at 298.15 K for this reaction. An estimated value of the standard molar entropy change = 3 J K-1 mol-1 for the above reaction was used together with the experimental value of to obtain a standard molar Gibbs free energy change ≈ −56 kJ mol-1 and an equilibrium constant K ≈ 7 × 109 for the conversion of chorismate2-(aq) to prephenate2-(aq) at 298.15 K. Thus, for all practical purposes, this reaction can be considered to be “irreversible”. Quantum mechanics (Gaussian 94 with a B3LYP functional and a 6-31G* basis set) was used to calculate values of absolute and...

55 citations

Journal ArticleDOI
TL;DR: In this paper, a large single crystal of barium tungstate (BaWO4) with dimensions of 22mmdiameter×80mm length was grown by the Czochralski method using an iridium crucible.
Abstract: A large single crystal of barium tungstate (BaWO4) with dimensions of 22-mmdiameter×80-mm length was grown by the Czochralski method using an iridium crucible. The melting point, molar enthalpy of fusion, and molar entropy of fusion of the crystal were determined to be 1775.10 K, 96913.80Jmol−1, and 54.60JK−1mol−1, respectively. The average linear thermal-expansion coefficients are αa=10.9526×10−6∕K, αb=10.8069×10−6∕K, and αc=35.1063×10−6∕K in the temperature range from 303.15 to 1423.15 K along the three respective crystallographic axes. The density of the crystal follows an almost linear decrease from 6.393×103 to 6.000×103kgm−3 when the temperature is increased from 303.15 to 1423.15 K. The measured specific heat are 115.56–130.96JK−1mol−1 in the temperature range of 323.15–1173.15 K. The thermal diffusion coefficient of the crystal was measured in the temperature range of 297.15–563.15 K. The calculated thermal conductivity is 2.256Wm−1K−1 along the [001] direction and 2.324Wm−1K−1 along the [100] dir...

55 citations

Journal ArticleDOI
01 Sep 2002
TL;DR: In this paper, the mixing enthalpies in the hematite-corundum solvus can be approximately reproduced by a symmetric, regular-like solution model.
Abstract: High-temperature oxide-melt calorimetry and Rietveld refinement of powder X-ray diffraction patterns were used to investigate the energetics and structure of the hematite–corundum solid solution and ternary phase FeAlO3 (with FeGaO3 structure). The mixing enthalpies in the solid solution can be described by a polynomial ΔHmix=WX hem(1−X hem) with W=116 ± 10 kJ mol−1. The excess mixing enthalpies are too positive to reproduce the experimental phase diagram, and excess entropies in the solid solution should be considered. The hematite–corundum solvus can be approximately reproduced by a symmetric, regular-like solution model with ΔG excess=(W H −TW S )X hem X cor, where W H= 116 ± 10 kJ mol−1 and W S =32 ± 4 J mol−1 K−1. In this model, short-range order (SRO) of Fe/Al is neglected because SRO probably becomes important only at intermediate compositions close to Fe:Al=1:1 but these compositions cannot be synthesized. The volume of mixing is positive for Al-hematite but almost ideal for Fe-corundum. Moreover, the degree of deviation from Vegard's law for Al-hematite depends on the history of the samples. Introduction of Al into the hematite structure causes varying distortion of the hexagonal network of oxygen ions while the position of the metal ions remains intact. Distortion of the hexagonal network of oxygen ions attains a minimum at the composition (Fe0.95Al0.05)2O3. The enthalpy of formation of FeAlO3 from oxides at 298 K is 27.9 ± 1.8 kJ mol−1. Its estimated standard entropy (including configurational entropy due to disorder of Fe/Al) is 98.9 J mol−1 K−1, giving the standard free energy of formation at 298 K from oxides and elements as +19.1 ± 1.8 and −1144.2 ± 2.0 kJ mol−1, respectively. The heat capacity of FeAlO3 is approximated as C p (T in K)= 175.8 − 0.002472T − (1.958 × 106)/T 2− 917.3/T 0.5+(7.546 × 10−6) T 2 between 298 and 1550 K, based on differential scanning calorimetric measurements. No ferrous iron was detected in FeAlO3 by Mossbauer spectroscopy. The ternary phase is entropy stabilized and is predicted to be stable above about 1730 ± 70 K, in good agreement with the experiment. Static lattice calculations show that the LiNbO3-, FeGaO3-, FeTiO3-, and disordered corundum-like FeAlO3 structures are less stable (in the order in which they are listed) than a mechanical mixture of corundum and hematite. At high temperatures, the FeGaO3-like structure is favored by its entropy, and its stability field appears on the phase diagram.

55 citations

Journal ArticleDOI
TL;DR: In this article, the Atoms and Bonds approach is applied to the estimation of thermodynamic and physical properties of hydrocarbons, including the standard enthalpy of formation, standard entropy, normal boiling point, standard enthpy of vaporization, critical pressure, critical temperature, and critical volume.
Abstract: Fast and reliable estimation of thermodynamic and physical properties of organic compounds is essential for the analysis and design of chemical processing systems. The ABC approach is based on the contributions of Atoms and Bonds in the properties of Conjugate forms of a molecular structure. The principles of this approach are applied to the estimation of thermodynamic and physical properties of hydrocarbons. Standard enthalpy of formation, standard entropy, normal boiling point, standard enthalpy of vaporization, critical pressure, critical temperature, and critical volume are estimated. Compared to a group-contribution approach, the ABC technique is more accurate, and it involves the same or substantially smaller number of parameters

55 citations


Network Information
Related Topics (5)
Aqueous solution
189.5K papers, 3.4M citations
85% related
Adsorption
226.4K papers, 5.9M citations
81% related
Crystallization
81.9K papers, 1.5M citations
81% related
Ionic liquid
57.2K papers, 1.6M citations
80% related
Nucleation
63.8K papers, 1.6M citations
79% related
Performance
Metrics
No. of papers in the topic in previous years
YearPapers
202316
202229
202141
202055
201949
201857