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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 second and third reactions in the metabolic pathway leading to the formation of chorismate were analyzed in terms of a chemical equilibrium model that accounts for the multiplicity of ionic states of the reactants and products.

10 citations

Journal ArticleDOI
TL;DR: In this article, a fungal extract-based bio-nanosorbent was prepared and used as an efficient biosorbent for the removal of heavy metals, namely Cu(II) and Ni(II), from aqueous solutions.
Abstract: Adsorption is very economical and environmentally friendly method that is commonly accepted as a promising technique for the removal of heavy metals. In this study a fungal-extract-based (FE-CB) bio-nanosorbent was prepared and used as an efficient biosorbent for the removal of heavy metals, namely Cu(II) and Ni(II), from aqueous solutions. FE-CB was characterized by scanning electron microscope, Brunauer–Emmett–Teller surface area and porosity analyzer, Fourier transform infrared, x-ray diffraction, differential scanning calorimeter, thermalgravimetric analysis and zeta potential. The Brunauer–Emmett–Teller surface area, pore volume and average pore diameter of FE-CB were 7.43 m2/g, 0.060 cm3/g, and 2.82 nm, respectively. The adsorbtion properties of FE-CB onto both Cu(II) and Ni(II) were investigated in terms of biosorbent dosage, temperature, initial concentration of Cu(II) and Ni(II) ions, pH and contact time in the batch experiments. The dependence of the biosorption mechanism on pH was revealed and the optimum pH was determined as 6 for Ni(II) and 5 for Cu(II). The Langmuir and Freundlich isothermal models and the kinetic Pseudo-first-order and Pseudo-second-order kinetic models were used to describe the adsorption performance of FE-CB. The activation energy was calculated by pseudo-second-order rate constants. In addition, thermodynamic parameters, standard Gibbs free energy, standard enthalpy and standard entropy were analyzed using the (Van’t Hoff equation). The biosorption process was found to be spontaneous, favorable and endothermic.

10 citations

Journal ArticleDOI
TL;DR: In this article, the heat capacity of anhydrous low Fe-cordierite, Fe2Al4Si5O18, was measured for the first time between 5 and 300 K on a milligram-sized synthetic sample using low-temperature heat-pulse calorimetry.
Abstract: The heat capacity of anhydrous low Fe-cordierite, Fe2Al4Si5O18, was measured for the first time between 5 and 300 K on a milligram-sized synthetic sample using low-temperature heat-pulse calorimetry. The C-p's of anhydrous low Mg-cordierite, Mg2Al4Si5O18, and a hydrous low Mg-cordierite of composition Mg1.97Al3.94Si5.06O18.0.625H(2)O, both previously studied by adiabatic calorimetry (Paukov et al., 2006, 2007), were also determined. At low temperatures around 10 K the C-p data for Fe-cordierite show a small feature that is interpreted as a Schottky anomaly. Using published DSC and adiabatic calorimetry results for anhydrous Fe-cordierite and Mg-cordierite and the results herein, Cp polynomials for both phases were calculated for use at T > 270 K. They are given by: C-p(Fe-Cd) = 91 1.1(+/- 9.7) - 5829.2(+/- 363) x T-0.5 - 13.9424(+/- 2.522) x 10(6) x T-2 + 1470.4(+/- 454.84) x 10(6) x T-3 and C-p(Mg-Cd) = 882.0(+/- 4.9) - 5155.8(+/- 167) x T-0.5 -20.7584(+/- 0.806) x T-2 + 2736.0(+/- 112.73) x 10(6) x T-3, respectively. The standard calorimetric entropy values at 298.15 K, SO, for anhydrous Fe-cordierite, anhydrous Mg-cordierite and hydrous Mg-cordierite are 460.5 +/- 0.5, 406.1 +/- 0.4 and 450.9 +/- 0.5 J/(mol.K), respectively. The latter two values are in good agreement with those determined by adiabatic calorimetry. The lattice (vibrational) and non-lattice contributions to the experimental C-p values for Fe-cordierite were separated by applying the Komada-Westrum model and the values S degrees(vib) = 447.7 J/(mol.K) and S-el(o) = 13.6 J/(mol.K) were obtained for the vibrational and electronic contributions to the standard third-law entropy. Thermodynamic calculations and analysis were carried out in the system FeO-Al2O3-SiO2 with and without H2O. A model C-p polynomial for hydrous Fe-cordierite, Fe2Al4Si5O18 center dot H2O, was derived as: C-p(hFe-Cd) = 967.3(+/- 9.7) - 6070.4(+/- 363) x T-0.5 - 13.9389(+/- 2.522) x 10(6) x T-2 + 1470.4(+/- 454.84) x 10(6) x T-3. The enthalpy of formation from the elements for both hydrous and anhydrous Fe-cordierite and the standard entropy for hydrous Fe-cordierite with one mole of H2O pfu were derived using the experimental phase equilibrium results of Mukhopadhyay & Holdaway (1994) on the reaction 3 Fe-cordierite center dot nH(2)O = 2 almandine + 4 sillimanite + 5 quartz + 3n H2O. For anhydrous Fe-cordierite Delta H-f(o) = -8448.26 kJ/mol was obtained and for hydrous Fe-cordierite, Delta H-f(o) = -8750.23 kJ/mol and S-o = 520.6 J/(mol.K). Phase relations in the FeO-Al2O3-SiO2-(H2O) systems at low pressures are analyzed and isohydrons for H2O in hydrous Fe-cordierite are modelled. H2O contents decrease with increasing temperature and increase with increasing pressure.

10 citations

Journal ArticleDOI
TL;DR: In this paper, the standard entropy of an inorganic solid is correlated to its formula unit volume via a linear equation, and the results of this analysis show that the standard entropies and/or molar volumes of the following phases deserve closer scrutiny: meta-ettringite phases, magnesium/aluminium layered double hydroxide solid solutions; almost all iron-bearing monosulfate and hydrogarnet phases; and several calcium silicate hydrate solid solution endmembers.

10 citations

Journal ArticleDOI
TL;DR: In this article, the standard entropy of solid elements and inorganic compounds have been related to atomic or molar volumes after grouping the substances according to the periodic classification, compound type and crystal structure.
Abstract: The standard entropies of solid elements and inorganic compounds have been related to atomic or molar volumes after grouping the substances according to the periodic classification, compound type and crystal structure. It is shown that, within each sub-group, standard entropy and molar volume are related by the expression S = aVn. For elements and simple compounds, the entropy increase between 298° K and the melting point is related parabolically to the respective temperature rise. The entropy increase for complex compounds is less than that for simple compounds and is also dependent on type of compound. Entropy of fusion is related to temperature in the same manner. It is indicated that the entropy of formation of solid products from solid reactants is directly proportional to the volume change during the reaction.

10 citations


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