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1.
Ben Abdelkader S. Ben Cherifa A. Coulet M. V. Khattech I. Rogez J. Jemal M. 《Journal of Thermal Analysis and Calorimetry》2004,77(3):863-871
Pure and well crystallised whitlockite Ca18Mg2H2(PO4)14 has been synthesized by precipitation from the magnesium and calcium nitrates and the diammonic phosphate. The product of
the reaction has been characterized by X-ray diffraction, IR spectroscopy and chemical analysis. Using differential conduction
calorimeters the enthalpies of solution of the whitlockite and of a mixture of the solid reactants - the tricalcium, the trimagnesium
and the dicalcium phosphates - have been measured at 25°C for various concentrations of solid in a 46 wt% nitric acid solution.
A combination of the enthalpies of solution with the enthalpies of formation of the reactants allows us to determine the standard
enthalpy of formation of the whitlockite. The value deduced, -27,93·103kJ mol-1, is compared to the standard enthalpies of formation of the trimagnesium and the tricalcium phosphates.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
2.
The standard molar enthalpies of formation
f
H
m
°
(l) at the temperature T = 298.15 K were determined using combustion calorimetry for N-methylpiperidine (A), N-ethylpiperidine (B), N-propylpiperidine (C), N-butylpiperidine (D), N-cyclopentylpiperidine (E), N-cyclohexylpiperidine (F), and N-phenylpiperidine (G). The standard molar enthalpies of vaporization
l
g
H
m
° of these compounds were obtained from the temperature variation of the vapor pressure measured in a flow system. From these data the following standard molar enthalpies of formation in gaseous phase
f
H
m
°
(g) were derived for: A –(61.39 ± 0.88); B –(88.1 ± 1.3); C –(105.81 ± 0.66); D –(126.2 ± 1.3); E ( –88.21 ± 0.75); F –(135.21 ± 0.94); G (70.3 ± 1.4) kJ · mol–1. They are used to determine the strain enthalpies of the cyclic amines A–G. The N-alkylated piperidine rings have been found to be about strainless. 相似文献
3.
Verevkin Sergey P. Beckhaus Hans-Dieter Schüle Ursula Rüchardt Christoph 《Structural chemistry》1998,9(1):1-7
The standard molar enthalpies of formation H
f
00B0;
(liq) at the temperature t = 298.15 K were determined using combustion calorimetry for N-methyl-3-methyl-3-phenyl-2-butaneamine 1a, N,N-dimethyl-3-methyl-3-phenyl-2-butaneamine 1b N-methyl-2,3-dimethyl-3-phenyl-2-butaneamine 2a, and N,N-dimethyl-2,3-dimethyl-3-phenyl-2-butaneamine 2b. The standard molar enthalpies of vaporization H
vap
00B0;
of these compounds were obtained from the temperature variation of the vapor pressure measured in a flow system. The following standard molar enthalpies of formation in gaseous phase H
f
00B0;
(g) are obtained from these data: for 1a – 10.9 ± 1.9; 1b – 3.6 ± 1.8; 1c – 26.6 ± 1.4, and 1d – 23.0 ± 1.8 kJ mol–1. From the standard molar enthalpies of formation for gaseous compounds which are available in the literature, improved values for the increments of the Benson group addivitiy scheme of amines were calculated. They are used to determine the strain enthalpies of the amines 1 and 2 from this investigation. 相似文献
4.
The standard molar enthalpies of formation
f
H
m
°
(cr) at the temperature T = 298.15 K were determined using combustion calorimetry for di-tert-butyl-methanol (A), di-tert-butyl-iso-propyl-methanol (B), and di-phenyl-methyl-methanol (C). The standard molar enthalpies of sublimation
cr
8
H
m
°
of these compounds and of di-phenyl-methanol (D) were obtained from the temperature variation of the vapor pressure measured in a flow system. Molar enthalpies of fusion
cr
1
H
m
°
of the compounds A–D and of tri-phenyl-methanol (E) were measured by differential scanning calorimeter (DSC). From these data and data available from the literature, the following standard molar enthalpies of formation in gaseous phase
f
H
m
°
(g) for A, (–397.0 ± 1.2); B, (–418.1 ± 2.3); C, (–34.2 ± 1.3); and D, (0.9 ± 2.1) kJ · mol–1 were derived, which correspond to strain enthalpies (H
S) of 46.1, 114.7, 8.1, and 5.0 kJ · mol–1, respectively. 相似文献
5.
The standard molar enthalpies of vaporization
l
g
H
m
º
of 2,5-dimethylfuran, 2-tert-butylfuran, 2,5-di-tert-butylfuran, cyclopentenyl methyl ether, cyclohexenyl methyl ether, and tert-amyl methyl ether were obtained from the temperature variation of the vapor pressure measured in a flow system. The standard (p° = 0.1 MPa) molar enthalpies of formation f H
m
º
(1) at the temperature T = 298.15 K were measured using combustion calorimetry for 2,5-dimethylfuran, 2-tert-butylfuran, and 2,5-di-tert-butylfuran. From the derived standard molar enthalpies of formation for gaseous compounds, ring correction terms and non-nearest neighbor interactions useful in the application of the Benson group additivity scheme were calculated. 相似文献
6.
7.
Monoclinicammoniumparatlingstate,(NH.),,H,W,,O.,4H,O(s),isanessentialintermediatecompoundintheextractionoftungstenfromitsoresl.Theknowledgeofthepropertiesofammoniumparatungstateisdesirableforcontrollingitscrystallizationanditsthermaldecomposition.However,thestudyonthethermodynamicpropertieshasnotbeenreported.Inthepresentwork,theenthalpyofreactionforthethermaldecompositionofammoniumparatungstatewasmeasured,anditsstandardenthalpyofformationat298.15Kisobtained.Thesampleofmonoclinicanunoniumpa… 相似文献
8.
以L-苏糖酸钙与草酸的复分解反应得到的L-苏糖酸溶液,在80℃下与过量 CoO反应较长时间,滤液浓缩后加无水乙醇制得L-苏糖酸钴粉红色粉末。用化学分 析及元素分析确定其组成为Co(C4H7O5)·H2O,IR光谱分析结果表明新化合物中苏糖 酸以羧基氧原子与Co^+配位。TD-DTG结果说明,它在热分解中有一定稳定性,经 脱水生成Co-(C4H7O5)2,最后生成CoO。用转动弹热量计测得其恒容燃烧能ΔcE为( -3504.47±1.64)kJ·mol^-1,计算得其标准燃烧焓和标准生成焓ΔfHm^θ分别为 (-3501.99±1.64)和(-2170.67±1.97)kJ·mol^-1。 相似文献
9.
10.
用溶解量热法,以KIO_4和KOH组成的弱碱性溶液为量热溶剂,设计3个不同的热化学循环,用RD-1型热导式自动量热计测定了MoO_3的标准生成焓,并推荐其值为ΔH_(t(moO_3))~0(298.15K)=-765.0±6.8kJ·mol~(-1)。 相似文献
11.
Yu. V. Maksimuk V. D. Sokolov V. M. Sevruk P. K. Trahanov 《Journal of Thermal Analysis and Calorimetry》2001,65(3):965-970
The enthalpies of combustion for 4-formylbenzoic acid (I), 4-methylbenzyl alcohol (II), and trimethyl 1,2,4-benzenetricarboxylate
(III) were determined by the bomb calorimetry method. Enthalpies of sublimation for I and II were measured with a calorimeter.
The contributions of different substituents to the standard enthalpies of formation for benzene derivatives in the gas state
were derived.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
12.
A calorimetric study of alloy formation in Au-Cu and Au-In systems was carried out. The heats of mixing, ΔH
mix, were measured at 1380,1484 and 1604 K for Au-Cu and at 1387, 1449 and 1505 K for Au-In in the full concentration range.
The results of experiments were described by approximating equations. Observed values of ΔH
mix were discussed using the phase diagrams of the systems. It was shown that the systems become closer to the ideal state with
increasing temperature. From the experimental data, the dependencies of the enthalpies of the systems on the composition and
temperature were estimated. The simultaneous effects of composition and temperature on enthalpy are represented in 3D diagrams.
The specific heats of the alloys, in the temperature range of experiments, were derived from the slopes of enthalpy planes.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
13.
14.
Y. M. Dan Y. R. Zhao Y. Liu S. S. Qu 《Journal of Thermal Analysis and Calorimetry》2006,84(3):531-534
The two complexes, [Ln(Ala)2(Im)(H2O)](ClO4)3 (Ln=Pr,
Gd), were synthesized and characterized. Using a solution-reaction isoperibol
calorimeter, standard enthalpies of reaction of two reactions: LnCl3⋅6H2O(s)+2Ala(s)+Im(s)+3NaClO4(s)=[Ln(Ala)2(Im)(H2O)](ClO4)3(s)+3NaCl(s)+5H2O(l) (Ln=Pr, Gd),
at T=298.15 K, were determined to be (39.26±0.10)
and (5.33±0.12) kJ mol–1 , respectively.
Standard enthalpies of formation of the two complexes at T=298.15
K, ΔfHΘm
{[Ln(Ala)2(Im)(H2O)](ClO4)3(s)} (Ln=Pr, Gd),
were calculated as –(2424.2±3.3) and –(2443.4±3.3)
kJ mol–1 , respectively. 相似文献
15.
在(298.15 ±0.01) K下用转动弹热量计测定了离子液体硫酸乙酯-1-甲基-3-乙基咪唑(EMIES)及合成它的原料1-甲基咪唑的恒容燃烧热,通过计算得到它们的标准燃烧焓 分别为(-2671±2) 和(-286.3±0.5) kJ·mol-1;标准生成焓 分别为(-3060±3) kJ·mol-1和(-2145±4) kJ·mol-1.结合文献上硫酸二乙酯的标准生成焓数据,得到了合成离子液体EMIES的反应热(-102.3±1.0) kJ·mol-1,与合成实验中观察到的强烈放热现象是一致的.根据离子液体EMIES的热容数据,计算了不同温度下EMIES的标准生成焓. 相似文献
16.
碳酸盐标准生成焓的计算 总被引:1,自引:0,他引:1
碳酸盐标准生成焓的计算戴长文,王振民,徐琰,戴晓弘(郑州大学化学系,郑州,450052)(郑州高新技术开发区,郑州,450001)关键词热力学性质,标准生成焓,碳酸盐预测无机化合物生成热的计算方法已见报道[1,2],但引入经验参数过多,且计算偏差亦较... 相似文献
17.
CHEN San-ping WEI Qing JIAO Bao-juan GAO Sheng-li ** Shaanxi Key Laboratory of Physico-Inorganic Chemistry Department of Chemistry Northwest University Xi′an P. R. China 《高等学校化学研究》2003,19(4):459-463
IntroductionThe pyrimidine and its derivatives are knownto possess extraordinary biological properties thatare generally distinguished qualitatively by havingbeen used as pesticide,herbicide,bactericide,andmedicine intermediates[1] .A survey of these appli-cations and a number of the related variations thathave been developed recently,such as the extraor-dinary effective herbicide of sulfonyl sulfourea,re-veals that the biological properties are just becauseof the wide existence of pyrimidine … 相似文献
18.
Thepyrimidinesasaclassareknowntopossessextraordinarybiologicalpropertiesthataregenerallydistinguishedqualitativelybytheirapplicationsinpesticide,herbicide,bactericide,andmedicineinter-mediates犤1犦.Asurveyoftheseapplicationsandanum-beroftherelatedvariationsthataredevelopedrecent-ly,suchastheextraordinaryeffectiveherbicideofsulfonylsulfourea,revealsthebroadbiologicalimpor-tancejustbecauseofthewideoccurrenceofpyrimi-dinesringsystemsinthesemolecules犤2犦.Ithasbeenshownthatthemedicineintermediates… 相似文献
19.
20.
合成了通式为RE(NCS)_3·5DMSO的7种稀土元素异硫氰酸盐与二甲基亚砜的固态配合物(RE=La,Ce,Pr,Nd,Sm,Eu,Gd)。运用本文设计的热化学循环,采用量热法,测定了上述7种配合物在298.15K时的标准生成焓,并计算了它们的晶格能。 相似文献