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.
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TL;DR: In this article, the effects of substituent groups in carboxylate anions on densities and surface tensions of these ionic liquids have been assessed from the analysis of the structure-property relat...
Abstract: In this work, four 1-butyl-3-methylimidazolium carboxylate ionic liquids (ILs) with different substituent groups in anions, including 1-butyl-3-methylimidazolium glycollate [C4mim][HOCH2COO], 1-butyl-3-methylimidazolium lactate [C4mim][CH3CHOHCOO], 1-butyl-3-methylimidazolium benzoate [C4mim][C6H5COO], and 1-butyl-3-methylimidazolium glycinate [C4mim][H2NCH2COO], have been synthesized and characterized. Their densities (ρ) and surface tensions (γ) have been determined experimentally in the temperature range of (298.15 to 343.15) K. By using thermodynamic and empirical equations, molar volume (Vm), isobaric expansivity (αp), standard entropy (S°), lattice energy (UPOT), surface excess entropy (Ss), vaporization enthalpy (ΔlgHm0) and Hildebrand solubility parameter (δH) of these ILs have been derived from density and surface tension data. The effects of substituent groups in carboxylate anions on densities and surface tensions of these ILs have been assessed from the analysis of the structure–property relat...
22 citations
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14 Nov 2019TL;DR: Two analytical representations of the entropy and Gibbs free energy for carbonyl sulfide are reported, and the prediction procedures only involve six molecular constants of the carbonyL sulfide molecule.
Abstract: Many chemical and physical equilibrium conditions can be determined from minimizing the Gibbs free energies of the system. Efficient analytical representations of the entropy and Gibbs free energy of carbonyl sulfide remain elusive in the communality of science and engineering. Here, we report two analytical representations of the entropy and Gibbs free energy for carbonyl sulfide, and the prediction procedures only involve six molecular constants of the carbonyl sulfide molecule. In the temperature range from 300 to 6000 K, the average relative deviations of the predicted molar entropy and reduced Gibbs free energy values of carbonyl sulfide from the National Institute of Standards and Technology database are arrived at 0.150 and 0.189%, respectively.
22 citations
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TL;DR: In this paper, the structural phase transition from orthorhombic phase to tetragonal phase involved discrete decrease of oxygen content in Pr 2 NiO 4+ δ and the phase transition temperature, T p, decreased with decreasing P (O 2 ).
22 citations
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21 Feb 2007TL;DR: In this paper, the authors present results from low-temperature heat capacity measurements of spinels along the solid solution between MgAl2O4 and MgCr 2O4.
Abstract: We present results from low-temperature heat capacity measurements of spinels along the solid solution between MgAl2O4 and MgCr2O4. The data also include new low-temperature heat capacity measurements for MgAl2O4 spinel. Heat capacities were measured between 1.5 and 300 K, and thermochemical functions were derived from the results. No heat capacity anomaly was observed for MgAl2O4 spinel; however, we observe a low-temperature heat capacity anomaly for Cr-bearing spinels at temperatures below 15 K. From our data we calculate standard entropies (298.15 K) for Mg(Cr,Al)2O4 spinels. We suggest a standard entropy for MgAl2O4 of 80.9 ± 0.6 J mol−1 K−1. For the solid solution between MgAl2O4 and MgCr2O4, we observe a linear increase of the standard entropies from 80.9 J mol−1 K−1 for MgAl2O4 to 118.3 J mol−1 K−1 for MgCr2O4.
22 citations
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TL;DR: In this paper, the authors identify the topological or configurational degrees of freedom in dense liquids as continuous line defects, labelled by the two-element group Z2, and yield a topological contribution to the latent heat of melting.
Abstract: The authors identify the topological or configurational degrees of freedom in dense liquids as continuous line defects, labelled by the two-element group Z2. These defects are absent in perfect solids, and yield a topological contribution to the latent heat of melting. The topological entropy is universal (for dense atomic liquids) and equals R ln 2 per mole, as observed experimentally. The same value is obtained for the topological, molar entropy of melting of (loose) covalent liquids. The topological entropy of sublimation of atomic substances is also calculated to be 4.69 R per mole.
22 citations