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Standard enthalpies of solution at 298 K of “A” type carbonate phosphobaryum hydroxyapatites versus the rate of CO 3 2− ions per unit cell Enthalpy of formation The direct measurement of

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Abstract  

The present work reports the experimental determination of the standard (p o = 0.1 MPa) molar enthalpies of formation in the condensed and gaseous phases, at T = 298.15 K, of 5- and 6-nitroindazole. These results were derived from the measurements of the standard molar energies of combustion, using a static bomb calorimeter and from the standard molar enthalpies of sublimation derived by the application of Clausius–Clapeyron to the temperature dependence of the vapour pressures measured by the Knudsen effusion technique. The results are interpreted in terms of the energetic contributions of the nitro groups in the different positions of the aromatic ring.

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data of the standard molar enthalpy of formation plays an important role in theoretical study, application development and industrial production of a compound as a basis of theoretical analysis. In this article, ZnO nanosheets with uniform size

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The standard enthalpies of formation of alkaline metals thiolates in the crystalline state were determined by reaction-solution calorimetry. The obtained results at 298.15 K were as follows:
\documentclass{aastex} \usepackage{amsbsy} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{bm} \usepackage{mathrsfs} \usepackage{pifont} \usepackage{stmaryrd} \usepackage{textcomp} \usepackage{upgreek} \usepackage{portland,xspace} \usepackage{amsmath,amsxtra} \pagestyle{empty} \DeclareMathSizes{10}{9}{7}{6} \begin{document} $$\Updelta_{\text{f}} H_{\text{m}}^{\text{o}} ({\text{MSR,}}\;{\text{cr}})$$ \end{document}
/kJ mol−1 = −259.0 ± 1.6 (LiSC2H5), −199.9 ± 1.8 (NaSC2H5), −254.9 ± 2.4 (NaSC4H9), −240.6 ± 1.9 (KSC2H5), −235.8 ± 2.0 (CsSC2H5). These results where compared with the literature values for the corresponding alkoxides and together with values for
\documentclass{aastex} \usepackage{amsbsy} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{bm} \usepackage{mathrsfs} \usepackage{pifont} \usepackage{stmaryrd} \usepackage{textcomp} \usepackage{upgreek} \usepackage{portland,xspace} \usepackage{amsmath,amsxtra} \pagestyle{empty} \DeclareMathSizes{10}{9}{7}{6} \begin{document} $$\Updelta_{\text{f}} H_{\text{m}}^{\text{o}} \left( {{\text{MSH}},\;{\text{cr}}}\right)$$ \end{document}
were used to derive a consistent set of lattice energies for MSR compounds based on the Kapustinskii equation. This allows the estimation of the enthalpy of formation for some non-measured thiolates.
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Lanthanum-bearing silicate-oxyapatites or britholites, Ca10–xLax(PO4)6–x(SiO4)xO with 1≤x≤6, have been synthesized by solid state reaction at high temperature. They were characterized by X-ray diffraction and IR spectroscopy. Using two microcalorimeters, the heat of solution of these compounds have been measured at 298 K in a solution of nitric and hydrofluoric acid. A strained least squares method was applied to the experimental results to obtain the solution enthalpies at infinite dilution, and the mixing enthalpy in two steps. In the first step the mixing enthalpy obtained is referenced to the britholite monosubstituted and to the oxysilicate. The mixing enthalpy referenced to the oxyapatite and to the oxysilicate is then extrapolated. In order to determine the enthalpies of formation of all the terms of the solution, thermochemical cycles were proposed and complementary experiments were performed. The results obtained show a decrease of the enthalpy of formation with the amount of Si and La introduced in the lattice. This was explained by the difference in the bond energies of (Ca–O, P–O) and (La–O, Si–O).

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The standard (p 0=0.1 MPa) molar enthalpy of formation, Δf H 0 m, for crystalline N-phenylphthalimide was derived from its standard molar enthalpy of combustion, in oxygen, at the temperature 298.15 K, measured by static bomb-combustion calorimetry, as –206.03.4 kJ mol–1. The standard molar enthalpy of sublimation, Δg cr H 0 m , at T=298.15 K, was derived, from high temperature Calvet microcalorimetry, as 121.31.0 kJ mol–1. The derived standard molar enthalpy of formation, in the gaseous state, is analysed in terms of enthalpic increments and interpreted in terms of molecular structure.

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The standard (p 0=0.1 MPa) molar enthalpy of formation, Δf H m 0(l)=169.8±2.6 kJ mol−1, of the liquid 3-bromoquinoline was derived from its standard molar energy of combustion, in oxygen, to yield CO2(g), N2(g) and HBr·600H2O(l), at T=298.15 K, measured by rotating bomb combustion calorimetry. The Calvet high temperature vacuum sublimation technique was used to measure the enthalpy of vaporization of the compound, Δ1 g H m 0=70.7±2.3 kJ mol−1. These two thermodynamic parameters yielded the standard molar enthalpy of formation, in the gaseous phase, at T=298.15 K, Δf H m 0(g)=240.5±3.5 kJ mol−1.

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Standard enthalpies of formation of amorphous platinum hydrous oxide PtH2.76O3.89 (Adams' catalyst) and dehydrated oxide PtO2.52 at T=298.15 K were determined to be -519.61.0 and -101.3 5.2 kJ mol-1, respectively, by micro-combustion calorimetry. Standard enthalpy of formation of anhydrous PtO2 was estimated to be -80 kJ mol-1 based on the calorimetry. A meaningful linear relationship was found between the pseudo-atomization enthalpies of platinum oxides and the coordination number of oxygen surrounding platinum. This relationship indicates that the Pt-O bond dissociation energy is 246 kJ mol-1 at T=298.15 K which is surprisingly independent of both the coordination number and the valence of platinum atom. This may provide an energetic reason why platinum hydrous oxide is non-stoichiometric.

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The standard enthalpy of combustion of crystalline silver pivalate, (CH3)3CC(O)OAg (AgPiv), was determined in an isoperibolic calorimeter with a self-sealing steel bomb, Δc H 0 (AgPiv, cr)= −2786.9±5.6 kJ mol−1. The value of standard enthalpy of formation was derived for crystalline state: Δf H 0(AgPiv,cr)= −466.9±5.6 kJ mol−1. Using the enthalpy of sublimation, measured earlier, the enthalpy of formation of gaseous dimer was obtained: Δf H 0(Ag2Piv2,g)= −787±14 kJ mol−1. The enthalpy of reaction (CH3)3CC(O)OAg(cr)=Ag(cr)+(CH3)3CC(O)O.(g) was estimated, Δr H 0=202 kJ mol−1.

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The standard (p 0=0.1 MPa) molar enthalpy of formation of 1-cyanoacetylpiperidine, in the crystalline state, at T=298.15 K, has been derived from measurements of its standard massic energy of combustion, by static bomb combustion calorimetry, as Δf H m 0=−217.1±1.4 kJ mol−1. The standard molar enthalpy of sublimation was measured, at T=298.15 K, by the microcalorimetric sublimation technique as Δcr g H m 0=103.5±1.9 kJ mol−1.

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