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1.
The enthalpy of formation at 298.15 K of the polymer Al13O4(OH)28(H2O)3+8 and an amorphous aluminium trihydroxide gel was studied using an original differential calorimetric method, already developed for adsorption experiments, and aluminium-27 NMR spectroscopy data. ΔHf “Al13” (298.15 K) = ? 602 ± 60.2 kJ mole?1 and ΔHf Al(OH)3 (298.15 K) = ? 51 ± 5 kJ mole?1. Using theoretical values of ΔGR “Al13” and ΔGR Al(OH)3, we calculated ΔGf “Al13” (298.15 K) = ? 13282 kJ mole?1; ΔSf “Al13” (298.15 K) = + 42.2 kJ mole?1; ΔGf Al(OH)3 (298.15 K) = ? 782.5 kJ mole?1; and ΔSf Al(OH)3 (298.15 K) = + 2.4 kJ mole?1.  相似文献   

2.
The enthalpy of reaction between praseodymium metal and 1.07 n HCl and the enthalpy of solution of praseodymium trichloride in 1.07 n HCl and water were measured in a swinging isoperibol calorimeter at 298.15 K. The results were used to calculate the enthalpy of formation of the praseodymium ion in the state of an infinitely dilute aqueous solution, Δf H°298.15 Pr3+(sln, ∞H2O) = ?687.8 ± 1.7 kJ/mol.  相似文献   

3.
The heat capacities of Na2Tb(MoO4)(PO4) and K2Tb(MoO4)(PO4) were measured by adiabatic calorimetry at low temperatures (6.34–333.74 and 7.20–341.17 K, respectively). Smoothed thermal-capacities values were used to calculate the entropy, enthalpy increments, and reduced Gibbs energy. The respective values at 298.15 K are as follows: for Na2Tb(MoO4)(PO4), C p 0 (298.15 K) = 240.1 ± 0.2 J/(K mol), 0 (298.15 K) = 307.4 ± 0.4 J/(K mol), H 0(298.15 K) ? H 0(0) = 44.95 ± 0.03 kJ/mol, and Φ0(298.15 K) = 156.6 ± 0.5 J/(K mol); and for K2Tb(MoO4)(PO4): C p 0 (298.15 K) = 245.1 ± 0.1 J/(K mol), S 0(298.15 K) = 322.9 ± 0.1 J/(K mol), H 0(298.15 K) ? H 0(0) = 46.58 ± 0.02 kJ/mol, and Φ0(298.15 K) = 166.6 ± 0.2 J/(K mol). The noncooperative magnetic component of the heat capacity was estimated.  相似文献   

4.
A thermochemical study of natural lithium micas, iron-containing polylithionite and lepidolite, was performed on a high-temperature heat-flux Calvet microcalorimeter (Setaram, France). Melt solution calorimetry was used to measure the enthalpies of mineral formation from the elements Δf H°el (298.15 K), ?5989.3 ± 9.6 and ?5981.3 ± 6.3 kJ/mol, respectively. The drop method was used to determine the enthalpy increments heating of the micas over the temperature interval 444–973 K. The equations for the temperature dependences of the heat capacities and enthalpies of Fe-polylithionite and Fe-lepidolite were obtained. The S° (298.15 K) and Δf G°el (298.15 K) values were estimated. The thermodynamic functions of the micas were calculated over the temperature range 298.15–1000 K.  相似文献   

5.
A thermochemical study of natural aluminum hydroxosulfate Al2[(OH)4SO4] · 7H2O, aluminite (Nakhodka deposit, West Chukotka, Russia) is performed on a Tian-Calvet “Setaram” high-temperature heat-conducting microcalorimeter (France). The enthalpy of aluminite formation from simple compounds is obtained via the melt calorimetry of dissolution, Δf H (298.15 K) = ?4986 ± 21 kJ/mol.  相似文献   

6.
The enthalpies of reactions of La2CoO4(cr) and CoCl2(cr) with hydrochloric acid were measured with an isothermal-jacket calorimeter. The results obtained and the available literature data were used to calculate the standard enthalpy of formation of La2CoO4(cr) at 298.15 K, Δf H o = ?2179 ± 7 kJ/mol.  相似文献   

7.
The low-temperature heat capacity of K2MoO4 was measured by adiabatic calorimetry. The smoothed heat capacity values, entropies, reduced Gibbs energies, and enthalpies were calculated over the temperature range 0–330 K. The standard thermodynamic functions determined at 298.15 K were C p ° (298.15 K) = 143.1 ± 0.2 J/(mol K), S°(298.15 K) = 199.3 ± 0.4 J/(mol K), H°(298.15 K)-H°(0) = 28.41 ± 0.03 kJ/mol, and Φ°(298.15 K) = 104.0 ± 0.4 J/(mol K). The thermal behavior of potassium molybdate at elevated temperatures was studied by differential scanning calorimetry. The parameters of polymorphic transitions and fusion of potassium molybdate were determined.  相似文献   

8.
Isopiestic vapor-pressure measurements were made for Li2SO4(aq) from 0.1069 to 2.8190 mol?kg?1 at 298.15 K, and from 0.1148 to 2.7969 mol?kg?1 at 323.15 K, with NaCl(aq) as the reference standard. Published thermodynamic data for this system were reviewed, recalculated for consistency, and critically assessed. The present results and the more reliable published results were used to evaluate the parameters of an extended version of Pitzer’s ion-interaction model with an ionic-strength dependent third-virial coefficient, as well as those of the standard Pitzer model, for the osmotic and activity coefficients at both temperatures. Published enthalpies of dilution at 298.15 K were also analyzed to yield the parameters of the ion-interaction models for the relative apparent molar enthalpies of dilution. The resulting models at 298.15 K are valid to the saturated solution molality of the thermodynamically stable phase Li2SO4?H2O(cr). Solubilities of Li2SO4?H2O(cr) at 298.15 K were assessed and the selected value of m(sat.)=3.13±0.04 mol?kg?1 was used to evaluate the thermodynamic solubility product K s(Li2SO4?H2O, cr, 298.15 K) = (2.62±0.19) and a CODATA-compatible standard molar Gibbs energy of formation Δf G m o (Li2SO4?H2O, cr, 298.15 K) = ?(1564.6±0.5) kJ?mol?1.  相似文献   

9.
The standard enthalpies of formation of liquid and gaseous octachlorotrisilane were estimated, Δf H o (298.15, Si3Cl8, g) = ?1397(9) kJ/mol and Δf H o (298.15, Si3Cl8, l) = ?1447(9) kJ/mol. The decomposition of Si3Cl8 over the temperature range 400–1000 K was studied theoretically.  相似文献   

10.
The vaporization of praseodymium triiodide was studied by high-temperature mass spectrometry. Monomeric (PrI3) and dimeric (Pr2I6) molecules and the PrI 4 ? and Pr2I 7 ? negative ions were recorded in saturated vapor over the temperature range 842–1048 K. The partial pressures of neutral vapor components were determined. The enthalpies of sublimation Δs H o(298.15 K) in the form of monomers (291 ± 10 kJ/mol) and dimers (400 ± 30 kJ/mol) were calculated by the second and third laws of thermodynamics. The equilibrium constants of ion-molecular reactions were measured and the enthalpies of the reactions determined. The enthalpies of formation Δf H o(298.15 K) of molecules and ions in the gas phase were calculated (?373 ± 11, ?929 ± 31, ?865 ± 25, and ?1433 ± 48 kJ/mol for PrI3, Pr2I6, PrI 4 ? , and Pr2I 7 ? , respectively).  相似文献   

11.
A calorimetric study of natural pyromorphite Pb5[PO4]3Cl was performed. Its enthalpy of formation was determined by melt solution calorimetry from elements Δf H el(298.15 K) = −4124 ± 20 kJ/mol. Value Δf G elo(298.15 K) = −3765 ± 20 kJ/mol was calculated.  相似文献   

12.
An isothermal-jacket calorimeter was used to measure the enthalpies of the reactions of LaCoO3(cr), LaCl3(cr), and CoCl2(cr) with a 2m hydrochloric acid solution. Based on these values and the published data, the standard enthalpy of formation of LaCoO3(cr) at 298.15 K was calculated (Δf H 0 = ?1232 ± 6 kJ/mol).  相似文献   

13.
The enthalpy of sublimation of benzamide was obtained by calorimetry in the range 323<T (K)<350. From values of ΔHsub(T)=f(T), it was possible to determine ΔH0sub (298.15 K)=101.7±1.0 kJ mole?1. Using previous data on ΔH0f (c, 298.15 K) obtained by combustion calorimetry, the value of ΔH0f (g, 298.15 K)=?100.9±1.2 kJ mole?1 was calculated. With the use of energetical values concerning thioacetamide, thiobenzamide and thiourea, on the one hand, and acetamide, benzamide and urea, on the other, a comparative study was made.  相似文献   

14.
The low-temperature heat capacity of Na2Lu (MoO4)(PO4) was measured by adiabatic calorimetry in the range of 7.47–345.74 K. The experimental data were used to calculate the thermodynamic functions of Na2Lu (MoO4)(PO4). At 298.15 K, the following values were obtained: C p 0 (298.15 K) = 237.7 ± 0.1 J/(K mol), S 0(298.15 K) = 278.1 ± 0.8 J/(K mol), H 0(298.15 K) ? H 0 (0 K) = 42330 ± 20 J/mol, and Φ0(298.15 K) = 136.1 ± 0. 3 J/(K mol). A heat capacity anomaly was found in the range of 10-67 K with a maximum at T tr = 39.18 K. The entropy and enthalpy of transition are ΔS = 12.39 ± 0.75 J/(K mol) and ΔH = 403 ± 16 J/mol. The thermal investigation of sodium lutetium molybdate phosphate in the high-temperature range (623–1223 K) was performed using differential scanning calorimetry. It was found that during melting in the range of 1030–1200 K, Na2Lu(MoO4)(PO4) degrades to simpler compounds; the degradation scenario is verified by X-ray powder diffraction.  相似文献   

15.
Five solid complexes of zinc with L‐α‐methionine, L‐α‐phenylalanine and L‐α‐histidine were prepared. The constant‐volume combustion energies of the complexes, ΔEc (coordination), were determined by a precise rotating bomb calorimeter at 298.15 K. They were ‐ 2969.03 ± 0.34, ‐2929.46 ± 1.59, ‐9597.13 ± 6.12, ‐4378.98 ± 3.27 and ‐14047 ± 6.75 kJ/mol, respectively. Their standard enthalpies of combustion, ΔHθm,c(coordination, s, 298.15 K), and standard enthalpies of formation, ΔHθm,f (coordination, s, 298.15 K), were calculated. They were ‐2959.73 ± 0.34, ‐2923.88 ± 1.59, ‐9649.18 ± 6.12, ‐4373.40 ± 3.27, ‐14048.53 ± 6.75 kj/mol and ‐1180.94 ± 0.92, ‐1401.26 ± 1.77, ‐2501.69 ± 6.50, ‐1381.47 ± 3.49, ‐1950.19 ± 7.65 kJ/mol, respectively.  相似文献   

16.
It was shown that the published data on the thermodynamic properties of aluminum monooxycarbide Al2OC (ed) are not consistent with the phase diagram of the Al2O3-Al4C3 system. A thermodynamic modeling of the equilibrium state of the Al2O3-Al4C3 system made it possible to obtain new estimates of the standard entropy and enthalpy of formation of aluminum monooxycarbide: S°(298.15 K, cd. Al2OC) = 45.3 J/(K mol) and Δf H°(298.15 K, cd, Al2OC) = ?625.6 kJ/mol.  相似文献   

17.
A thermochemical study of partheite of composition (Ca1.96Mg0.04Na0.01K0.01) · [(Al4.04Fe 0.01 3+ )Si3.95O14.97(OH)2.03] · 4.2H2O, a natural calcium zeolite extracted from gabbro pegmatites of the Denezhkin Kamen’ deposit (North Ural, Russia), was performed. The enthalpies of formation of partheite from the constituent oxides, (Δf H°ox(298.15 K) = ?359 ± 21), and elements, (Δf H°el(298.15 K) = ?10108 ± 21), were determined by means of high-temperature in-melt-dissolution calorimetry. On the basis of the experimental data obtained, the enthalpy of formation of partheite of theoretical composition Ca2[Al4Si4O15(OH)2] · 4H2O from the elements was evaluated, ?10052 ± 21 kJ/mol.  相似文献   

18.
Microcalorimetric measurements at 520–523 K of the heats of thermal decomposition and of iodination of bis-(benzene)molybdenum and of bis-(toluene)tungsten have led to the values (kJ mol?): ΔHof[Mo(η-C6H6)2, c] = (235.3 ± 8) and ΔHof[W(η6-C7H8)2, c] = (242.2 ± 8) for the standard enthalpies of formation at 25°C. The corresponding ΔHof(g) values, using available and estimated enthalpies of sublimation, are (329.9 ± 11) and 352.2 ± 11) respectively, from which the metalligand mean bond-dissociation enthalpies, D(Mo—benzene) = (247.0 ± 6) and D(W—toluene) = (304.0 ± 6) kJ mol?1, are derived.  相似文献   

19.
Adiabatic calorimetry is used to measure the low-temperature heat capacity of Na2Er(MoO4)(PO4)from 6.41 to 347.87 K. Experimental data are used to calculate the thermodynamic functions of Na2Er(MoO4)(PO4), which at 298.15 K are as follows: C p 0 (298.15 K) = 243,3 ± 0.4 J/(K mol), S 0(298.15 K) = 312.8 ± 0.8 J/(K mol), H 0(298.15 K) ? H 0(0 K) = 45280 ± 90 J/mol, and Φ0(298.15 K) = 136.1 ± 0.3 J/(K mol). A diffuse heat-capacity anomaly associated with splitting of the Stark levels (Schottky anomaly) is discovered in the low-temperature region.  相似文献   

20.
For a set of 32 selected free radicals, energy minimum structures, harmonic vibrational wave numbers ωe, principal moments of inertia IA, IB, and IC, heat capacities C°p(T), entropies S°(T), thermal energy contents H°(T) ? H°(0), and standard enthalpies of formation ΔfH°(T) were calculated at the G3MP2B3 level of theory in the temperature range 200–3000 K. In this article, thermodynamic functions at T = 298.15 K are presented and compared with recent experimental values. The mean absolute deviation between calculated and experimental ΔfH°(298.15) values resulted in 3.91 kJ mol?1, which is close to the average experimental uncertainty of ± 3.55 kJ mol?1. The influence of hindered rotation on thermodynamic functions is studied for isopropyl and tert‐butyl radicals. © 2002 Wiley Periodicals, Inc. Int J Chem Kinet 34: 550–560, 2002  相似文献   

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