Authors:Gaochao Fan, Zaiyin Huang, Junying Jiang, and Li Sun
data of the standard molar enthalpyofformation 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
By using a DSK of the French firm Seteram, the standard enthalpies of formation of 5 tellurites and 5 tetratellurites of the
rare earths Gd, Tb, Dy, Tm and Yb were determined for the first time.
Three parallel determinations for each sample were compared. The results are very similar, which is an indication of the great
reliability of the method used and the correctness of the data obtained.
Authors:K. Ardhaoui, J. Rogez, A. Ben Chérifa, M. Jemal, and P. Satre
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).
The standard (p0=0.1
MPa) molar enthalpy of formation, ΔfH0m, 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, ΔgcrH0m
, 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
Authors:V. Lukyanova, T. Papina, K. Didenko, and A. Alikhanyan
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, ΔcH0 (AgPiv, cr)= −2786.9±5.6 kJ mol−1. The value of standard enthalpy of formation was derived for crystalline state: ΔfH0(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: ΔfH0(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, ΔrH0=202 kJ mol−1.
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.
The standard (p0=0.1 MPa) molar enthalpy of formation, ΔfHm0(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, Δ1gHm0=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, ΔfHm0(g)=240.5±3.5 kJ mol−1.
The standard (p0=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 ΔfHm0=−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 ΔcrgHm0=103.5±1.9 kJ mol−1.
of the liquid 2-methylfuran, 5-methyl-2-acetylfuran and 5-methyl-2-furaldehyde were derived from the standard molar energies
of combustion, in oxygen, at T = 298.15 K, measured by static bomb combustion calorimetry. The Calvet high temperature vacuum sublimation technique was
used to measure the enthalpies of vaporization of the three compounds. The standard (po = 0.1 MPa) molar enthalpies of formation of the compounds, in the gaseous phase, at T = 298.15 K have been derived from the corresponding standard molar enthalpies of formation in the liquid phase and the standard
molar enthalpies of vaporization. The results obtained were −(76.4 ± 1.2), −(253.9 ± 1.9), and −(196.8 ± 1.8) kJ mol−1, for 2-methylfuran, 5-methyl-2-acetylfuran, and 5-methyl-2-furaldehyde, respectively.