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71.
Sergio Cabani Paolo Gianni Vincenzo Mollica Luciano Lepori 《Journal of solution chemistry》1981,10(8):563-595
The thermodynamic properties G
h
o,H
h
o, and C
p,h
oassociated with the transfer of non-ionic organic compounds from gas to dilute aqueous solution and the limiting partial molar properties C
p
o
,2 and V2
2 of these compounds in water are described through a simple scheme of group contributions. A distinction is made between groups made only of carbon and hydrogen, and functional groups i.e. groups containing at least one atom different from carbon and hydrogen. Each group is assigned a contribution, for each property, through a least squares procedure which utilizes only molecules containing at most one functional group. Finally, for compounds containing more than one functional group, correction parameters are evaluated as the differences between the experimental values and those calculated by means of the group contributions. The different behavior of hydrophilic compared with hydrophobic groups is discussed for the various properties. A rationale for the correction parameters, i.e. for the effects of the interactions among hydrophilic groups on the thermodynamic properties, is attempted. 相似文献
72.
On the Thermodynamics of Vaporization and the Enthalpies of Formation of CaSe, SrSe and BaSe The congruent vaporization of the solid compounds CaSe, SrSe and BaSe of stoichiometric composition was studied over the temperature ranges 1832?2138 K, 1862?2122 K and 1860?2158 K, respectively, by the Knudsen effusion weight-loss method. Using enthalpy and entropy data from the literature for gaseous M, MSe, Se2 and Se (M = Ca, Sr, Ba) and estimated data for the standard entropies and enthalpy functions of solid MSe, it can be shown that within the given temperature ranges CaSe and SrSe vaporize predominatly to the atomic species, while in case of BaSe the mode of vaporization to the atoms and to the molecular species BaSe are of about equal importance. The Se2-content of the gas phase is very small in all cases. The following second and third law enthalpies and entropies (indices II and III respectively) were derived for the vaporization to the gaseous elements: see “Inhaltsübersicht”. The following standard enthalpies of formation of MSe(s) were derived from the third law enthalpies (in kJ · mol?1): CaSe: ?445 ± 44; SrSe: ?451 ± 42; BaSe: ?467 ± 44. 相似文献
73.
Christine Bonal Jean-Pierre Morel Nicole Morel-Desrosiers 《Journal of solution chemistry》1998,27(4):361-372
The apparent equilibrium constants and enthalpies of complexation of Nd3+, Sm3+, Eu3+, and Gd3+ by xylitol in aqueous solutions containing NaNO3 at an ionic strength of 2.0 mol-kg–1 have been determined by microcalorimetry at 25°C. Since nitrate anion weakly complexes the lanthanide cations, these values are analyzed in terms of competition between xylitol and NO
3
-
The method leads to the apparent equilibrium constants and enthalpies of complexation of the lanthanide cations by NO
3
-
at this particular ionic strength. Despite the difficulties encountered in characterizing rather weak associations, the results are, whenever comparison is possible, in good agreement with those obtained by direct microcalorimetry. The advantage of this competition method is that it can be used when the enthalpic effects are too weak and insufficiently concentration dependent for direct microcalorimetric determination. In the present case, it allows us to thermodynamically characterize the formation of SmNO
3
2+
and EuNO
3
2+
, processes we have not been able to study directly. 相似文献
74.
S.?Didaoui-NemouchiEmail author A.?Ait-Kaci M.?Rogalski 《Journal of Thermal Analysis and Calorimetry》2005,79(1):85-88
Enthalpies of mixing H have been measured for liquid binary mixtures of diisopropylether (DIPE)+benzene or cyclohexane and for liquid ternary mixtures diisopropylether+benzene+cyclohexane at 303.15 K and constant pressure using a C80 calorimeter. A Redlich-Kister type equation was used to correlate experimental results. 相似文献
75.
M. Asmann A. Wank H. Kim J. Heberlein E. Pfender 《Plasma Chemistry and Plasma Processing》2001,21(1):37-63
Enthalpy probe measurements were taken of the converging plasma plume in a triple torch plasma reactor and related to substrate heat flux measurements. Results show excellent entrainment of process gases injected into the converging plasma plume by way of the central injection probe. At lower pressures (40 kPa), the plasma volume is equivalent to at least a 3 cm diameter, 4 cm long cylinder, with relatively uniform temperature, velocity, and substrate heat flux profiles when compared to a typical dc arc jet. Converging plasma plume size, substrate heat flux, and enthalpy profiles are also shown to be a strong function of applied system power. Substrate heat flux measurements show smaller radial gradients than enthalpy probe measurements, because of the high radial velocity component of gases above the substrate boundary layer. Enthalpy probe measurements were also conducted for diamond deposition conditions and approximate temperature and velocity profiles obtained. Problems with the uniform gas mixture assumption prohibited more accurate measurements. Reproducibility of enthalpy measurement results was shown with an average standard deviation of 11.8% for the velocity and 7.6% for the temperature measurements. 相似文献
76.
Valery P. Nesterenko 《Journal of Thermal Analysis and Calorimetry》2005,80(3):575-577
Summary On the basis of calorimetric research of selenium dioxide, zirconium dioxide and zirconium diselenite dissolution reactions in the hydrofluoric acid solution under 298 K a standard enthalpy of Zr(SeO3)2 formation reaction from ZrO2 and SeO2 and a standard enthalpy of zirconium diselenite formation have been obtained. The value of enthalpy has been equal to -58.1±3.43 kJ mol-1 in ZrO2(solid)+2SeO2(solid) Zr(SeO3)2(solid) reaction. The standard enthalpy of zirconium diselenite formation is equal to Hf,2980Zr(SeO3)2(solid)= -1603.2±3.8 kJ mol-1. The Hf,2980 Zr(SeO3)2(solid) value has been determined for the first time. 相似文献
77.
K. Ardhaoui J. Rogez A. Ben Chérifa M. Jemal P. Satre 《Journal of Thermal Analysis and Calorimetry》2006,86(2):553-559
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). 相似文献
78.
分子拓扑指数在晶格能中的应用凌天才(重庆师范学院化学系重庆630047)关键词拓扑指数,晶格能分子拓扑指数实际上是分子图的不变量。自wiener ̄[1]于1947年首次提出wiener指数并用以关联烃类的沸点等数据以来,分子拓扑指数广泛用于关联与预测... 相似文献
79.
H. Honda A. Oshima H. Hinode M. Wakihara 《Journal of Thermal Analysis and Calorimetry》1992,38(8):1939-1945
Enthalpy increment HT-H289K measurements have been made on iron Chevrel phase sulphide Fe2Mo6S7.8, in the temperature range 300 to 500 K by the drop method using a hightemperature Calvet-type twin calorimeter. The first-order phase transition of this sulphide from a triclinic (low-temperature phase) to a rhombohedral (high-temperature phase) occurred at 375 K, and the enthalpy was evaluated to be 6.0 kJ/mol. The heat capacities of iron Chevrel phase sulphide Fe2Mo6S7.8 were also calculated before and after the phase transition.
Zusammenfassung Nach der Tropfenmethode wurden mittels eines Hochtemperaturdoppelkalorimeters vom Typ Calvet im Temperaturbereich 300–500 K an Fe2Mo6S7.8Messungen der Enthalpieinkremente HT-H298K durchgeführt. Die Phasenumwandlung erster Ordnung bei diesem Sulfid von der triklinen (Niedertemperaturphase) in die rhomboedrische (Hoch-temperaturphase) erfolgt bei 375 K und die Enthalpie erhielt man mit einem Wert von 6.0 kJ/mol. Die Wärmekapazitäten für Fe2Mo6S7.8 wurden sowohl vor als auch nach der Phasenumwandlung berechnet.相似文献
80.
J. N. Spencer S. K. Berger C. R. Powell B. D. Henning G. S. Furman W. M. Loffredo E. M. Rydberg R. A. Neubert C. E. Shoop D. N. Blauch 《Journal of solution chemistry》1981,10(7):501-509
Enthalpies of solution and of transfer of amides for the solvents chloroform (CHCl3), methylenechloride (CH2Cl2), carbontetrachloride (CCl4), cyclohexane (C6H12), N,N-dimethylformamide (DMF), N,N-dimethylacetamide (DMA), and ethylacetate (EtOAc) have been used to isolate and quantify the solvation interactions of amides in chlorinated solvents. Specific interactions at the aminde carbonyl and N–H groups have been identified. An analysis of the transfer enthalpies of pyrrole and methylpyrrole from cyclohexane to the chlorinated solvents shows that specific interactions between the pyrroles and these solvents are similar in nature. A means of calculating differences in the transfers of different solutes between the same solvent pair is given.Work done at Lebanon Valley College. 相似文献