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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 article, the authors measured the oxygen nonstoichiometry of La{sub 2-x}Sr{sub x}CuO{sub 4-{delta}} (x = 0-0.3) using high-temperature gravimetry and coulometric titration.
62 citations
TL;DR: In this paper, a model for the octahedral disordering of Al as function of temperature and composition has been developed for calculating the configurational entropy and molar entropy of Al-opx; distinction has been made between the cases of completely random mixing of Al and Si in the tetrahedral B site, and of random mixing without violation of the "aluminum avoidance" principle.
Abstract: Orthopyroxene has two tetrahedral sites, designated A and B, and two octahedral sites, M1 and M2. Crystallographic studies of synthetic and natural orthopyroxenes (opx) suggest that the tetrahedral Al is ordered nearly completely in the B site, but the octahedral Al disorders between M1 and M2 sites with a preference for M1. If the ‘aluminum avoidance’ principle is obeyed, then the tetrahedral Si-Al ordering limits the Al substitution in opx to 25 mol%, thus leading to an end-member stoichiometry of Mg3Al2Si3O12 instead of MgAl2SiO6. The enthalpy of formation of these two components has been deduced from the available phase equilibrium data. The thermodynamic properties of the opx solid solution approximates ideal solution behavior more closely when treated in terms of the components Mg4Si4O12(QEn)-Mg3Al2Si3O12(Py) than when expressed in terms of the components Mg2Si2O6-MgAl2SiO6. A model has been developed for the octahedral disordering of Al as function of temperature and composition. These data enable calculation of the configurational entropy and molar entropy of Al-opx; distinction has been made between the cases of completely random mixing of Al and Si in the tetrahedral B site, and of random mixing without violation of the ‘aluminum avoidance’ principle. The second model yields entropy of the Mg3Al2Si3O12 end member which agrees almost exactly with the value derived from phase equilibrium data. The partial molal entropies of the Orthopyroxene components ‘QEn’ and ‘Py’ can be derived from these data; their implications with respect to the P-T slopes of Al2O3 isopleths for the equilibrium of Orthopyroxene with forsterite and spinel/garnet have been discussed.
62 citations
TL;DR: In this article, a solid state electrochemical technique has been used to obtain thermodynamic information on uraniathoria solid solutions of compositions UyTh1−yO2+x with values of y of 0.9 to 0.3 and values of x of 1.02 to 1.16.
Abstract: A solid state electrochemical technique has been used to obtain thermodynamic information on uraniathoria solid solutions of compositions UyTh1−yO2+x with values of y of 0.9 to 0.3 and values of x of 0.02 to 0.16. The electrochemical cells were of the type Fe,FeO | (ZrO2+CaO) | UyTh1−yO2+x, Pt. Measurements were made at temperatures of 1150–1350°K.Partial molar free energies, entropies, and enthalpies of solution of oxygen in the solid solutions were calculated. The partial molar free energy decreases negatively with increasing thorium content for thorium concentrations greater than 30 atomic percent. The partial molar entropy increases negatively with increasing oxygen content or with increasing thorium content.The experimental results are discussed in connection with a mechanism of interstitial solution of oxygen ions in the fluorite lattice. A thermodynamic equation for the entropy is developed which gives semiquantitative agreement with the experimental data.
61 citations
TL;DR: In this paper, the authors derived the partition coefficients of a homogeneous and normal distribution of p, t-octylphenoxyethoxyethoxideethanols (OPE1−10) in the system, isooctane-water, at 25°C.
60 citations
TL;DR: In this paper, the synthesis of nanoscale zerovalent manganese (nZVMn) by chemical reduction was carried out in a single pot system under inert environment.
Abstract: Synthesis of nanoscale zerovalent manganese (nZVMn) by chemical reduction was carried out in a single pot system under inert environment. nZVMn was characterized using a combination of analytical techniques: Ultraviolet–Visible Spectroscopy, Fourier Transform Infrared Spectroscopy, Scanning Electron Microscopy, Transmission Electron Microscopy, Energy Dispersive X-ray, BET surface area and Point of Zero Charge. The adsorption physicochemical factors: pH, contact time, adsorbent dose, agitation speed, initial copper ion concentration and temperature were optimized. The kinetic data fitted better to Pseudo second-order, Elovich, fractional power and intraparticle diffusion models and their validity was tested by three statistical models: sum of square error, Chi-square (χ
2) and normalized standard deviation (Δq). Seven of the two-parameter isotherm models [Freundlich, Langmuir, Temkin, Dubinin–Kaganer–Raduskevich (DKR), Halsey, Harkin–Jura and Flory–Huggins] were used to analyse the equilibrium adsorption data. The Langmuir monolayer adsorption capacity (Q
max = 181.818 mg/g) obtained is greater than other those of nano-adsorbents utilized in adsorption of copper ions. The equilibrium adsorption data were better described by Langmuir, Freundlich, Temkin, DKR and Halsey isotherm models considering their coefficient of regression (R
2 > 0.90). The values of the thermodynamic parameters: standard enthalpy change ∆H° (+50.27848 kJ mol−1), standard entropy change ∆S° (203.5724 J mol−1 K−1) and the Gibbs free energy change ∆G° revealed that the adsorption process was feasible, spontaneous, and endothermic in nature. The performance of this novel nanoscale zerovalent manganese (nZVMn) suggested that it has a great potential for effective removal of copper ions from aqueous solution.
60 citations