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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 authors measured the thermodynamic properties of three zeolite series having the same alumino-silicate framework: natrolite, mesolite, and scolecite.
Abstract: Calorimetric measurements have been carried out on specimens of natrolite, mesolite, and scolecite in order to assess the thermodynamic properties of a zeolite series having the same alumino-silicate framework. Low-temperature heat capacity and high-temperature enthalpy increments of natrolite and scolecite were measured by adiabatic and drop-calorimetric techniques. Standard enthalpies of formation at 298.15 K of all three zeolites were determined by solution calorimetry. Thermodynamic functions have been calculated for natrolite to 660 K and for scolecite to 470 K. The heat capacity and standard entropy at 298.15 K have been estimated for mesolite. With reference to zeolitic water, it is concluded that the entropy of water molecules in both natrolite and scolecite is similar to that in ice. A consideration of the X-ray results for the present specimen of natrolite leads to the conclusion that a contribution of about 9.2 J/(mol x K) to the standard entropy is made by the Al-Si disorder in the alumino-silicate framework. The new results allow calculations to be made by which the pressure and temperature effect can be deduced for such equilibria as: natrolite + SiO/sub 2/(aq) = 2 analcime, and natrolite + Ca/sup 2 +/(aq) + H/sub 2/O = mesolite + 2Na/sup +/(aq).more » Results are consistent with observed parageneses in natural occurrences. 21 references, 1 figure, 10 tables.« less
67 citations
TL;DR: The solubility of carefully characterized NiO has been measured from 423 to 573 K in a flow apparatus, using solutions whose composition ranged from HCl of molality 5 × 10−4 mol kg−1 to NaOH ofmolality 4 × 10 −2 mol kg −1.
66 citations
65 citations
TL;DR: An extension of Anderson's formulation of the defect theory of nonstoichiometry is used with an oxygen-interstitial oxygen-vacancy model to calculate the composition of the uranium dioxide phase at the lower phase boundary and the relative partial molar thermodynamic functions for oxygen at compositions ranging from the lower-phase boundary to UO2.08 as mentioned in this paper.
Abstract: An extension of Anderson's formulation of the defect theory of nonstoichiometry is used with an oxygen—interstitial oxygen‐vacancy model to calculate the composition of the uranium dioxide phase at the lower phase boundary and the relative partial molar thermodynamic functions for oxygen at compositions ranging from the lower phase boundary to UO2.08. The model is used as a basis on which to argue that differing experimental results near UO2.00 are more likely due to differing, nonequilibrium, concentrations of uranium vacancies than to failure to reach oxygen equilibrium. The present form of the model, with an interstitial site density of one per uranium site fails sharply at about UO2.08 rather than gradually as the oxygen content is increased from UO2.00. Discussion of the effects of alternate site densities is used to explain the observed values of the partial molar entropy of the oxygen in the range from UO2.02 to UO2.24.
65 citations
TL;DR: In this article, the effects of initial lead ion concentration, contact time, pH and temperature on the removal of Pb(II) systematically were evaluated by applying the van-t Hoff equation, which describes the dependence of equilibrium constant on temperature.
65 citations