共查询到20条相似文献,搜索用时 31 毫秒
1.
J. N. Zhang Z. C. Tan Q. F. Meng Q. Shi B. Tong S. X. Wang 《Journal of Thermal Analysis and Calorimetry》2009,95(2):461-467
The heat capacities (C
p,m) of 2-amino-5-methylpyridine (AMP) were measured by a precision automated adiabatic calorimeter over the temperature range
from 80 to 398 K. A solid-liquid phase transition was found in the range from 336 to 351 K with the peak heat capacity at
350.426 K. The melting temperature (T
m), the molar enthalpy (Δfus
H
m0), and the molar entropy (Δfus
S
m0) of fusion were determined to be 350.431±0.018 K, 18.108 kJ mol−1 and 51.676 J K−1 mol−1, respectively. The mole fraction purity of the sample used was determined to be 0.99734 through the Van’t Hoff equation.
The thermodynamic functions (H
T-H
298.15 and S
T-S
298.15) were calculated. The molar energy of combustion and the standard molar enthalpy of combustion were determined, ΔU
c(C6H8N2,cr)= −3500.15±1.51 kJ mol−1 and Δc
H
m0 (C6H8N2,cr)= −3502.64±1.51 kJ mol−1, by means of a precision oxygen-bomb combustion calorimeter at T=298.15 K. The standard molar enthalpy of formation of the crystalline compound was derived, Δr
H
m0 (C6H8N2,cr)= −1.74±0.57 kJ mol−1. 相似文献
2.
Mojtaba Shamsipur Mohsen Irandoust Kamal Alizadeh Vito Lippolis 《Journal of inclusion phenomena and macrocyclic chemistry》2007,59(3-4):203-209
Proton NMR was used to study the complexation reaction of Ag+ with octathia-24-crown-8 (OT24C8) in a number of binary dimethylsulfoxide (DMSO)–nitrobenzene (NB) mixtures at different
temperatures. In all cases, the exchange between free and complexed OT24C8 was fast on the NMR time scale and only a single
population average 1H signal was observed. The formation constants of the resulting 1:1 complexes in different solvent mixtures were determined
by computer fitting of the chemical shift-mole ratio data. There is an inverse relationship between the complex stability
and the amount of DMSO in the solvent mixtures. The enthalpy and entropy values for the complexation reaction were evaluated
from the temperature dependence of formation constants. In all solvent mixtures studied, the resulting complex is enthalpy
stabilized but entropy destabilized. The TΔS° versus ΔH° plot of all thermodynamic data obtained shows a fairly good linear correlation indicating the existence of enthalpy–entropy
compensation in the complexation reaction. 相似文献
3.
Molar heat capacity and thermodynamic properties of 1,2-cyclohexane dicarboxylic anhydride [C8H10O3]
X. -C. Lv X. -H. Gao Z. -C. Tan Y. -S. Li L. -X. Sun 《Journal of Thermal Analysis and Calorimetry》2008,92(2):523-527
The molar heat capacity C
p,m of 1,2-cyclohexane dicarboxylic anhydride was measured in the temperature range from T=80 to 390 K with a small sample automated adiabatic calorimeter. The melting point T
m, the molar enthalpy Δfus
H
m and the entropy Δfus
S
m of fusion for the compound were determined to be 303.80 K, 14.71 kJ mol−1 and 48.43 J K−1 mol−1, respectively. The thermodynamic functions [H
T-H
273.15] and [S
T-S
273.15] were derived in the temperature range from T=80 to 385 K with temperature interval of 5 K. The thermal stability of the compound was investigated by differential scanning
calorimeter (DSC) and thermogravimetry (TG), when the process of the mass-loss was due to the evaporation, instead of its
thermal decomposition. 相似文献
4.
As represented by equations in which there is a term representing the biomass, the thermodynamics of biological growth processes
is difficult to study without knowing the thermodynamic properties of cellular structural fabric. Measurement of the heat
capacity data required to determine the standard entropy, So
298,15 or the standard absorbed heat, (H
o
298,15
-ΔHo
0
=Θo
298,15 of biomass requires a low-temperature calorimter, and these are not present in most laboratories. Based on a previously described
method for entropy, two equations are developed that enable values of the absorbed heat (Θo
298,15) and the absorbed heat of formation, (Δ
f
Θo
298,15) for biomass to be calculated empirically which are accurate to within 1% with respect to the biomass substances tested.
These equations depend on a previous knowledge of the atomic composition or the unit-carbon formulas of macromolecules or
structural cellular fabric.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
5.
M.-H. Wang Z.-C. Tan Q. Shi L.-X. Sun T. Zhang 《Journal of Thermal Analysis and Calorimetry》2006,84(2):413-418
The
heat capacities of 2-benzoylpyridine were measured with an automated adiabatic
calorimeter over the temperature range from 80 to 340 K. The melting point,
molar enthalpy, ΔfusHm,
and entropy, ΔfusSm,
of fusion of this compound were determined to be 316.49±0.04 K, 20.91±0.03
kJ mol–1 and 66.07±0.05 J mol–1
K–1, respectively. The purity of the compound
was calculated to be 99.60 mol% by using the fractional melting technique.
The thermodynamic functions (HT–H298.15) and (ST–S298.15) were calculated based
on the heat capacity measurements in the temperature range of 80–340
K with an interval of 5 K. The thermal properties of the compound were further
investigated by differential scanning calorimetry (DSC). From the DSC curve,
the temperature corresponding to the maximum evaporation rate, the molar enthalpy
and entropy of evaporation were determined to be 556.3±0.1 K, 51.3±0.2
kJ mol–1 and 92.2±0.4 J K–1
mol–1, respectively, under the experimental
conditions. 相似文献
6.
F. Xu L.-X. Sun Z.-C. Tan J.-G. Liang Y.-Y. Di Q.-F. Tian T. Zhang 《Journal of Thermal Analysis and Calorimetry》2004,76(2):481-489
Molar heat capacities (C
p,m) of aspirin were precisely measured with a small sample precision automated adiabatic calorimeter over the temperature range
from 78 to 383 K. No phase transition was observed in this temperature region. The polynomial function of C
p,m
vs. T was established in the light of the low-temperature heat capacity measurements and least square fitting method. The corresponding
function is as follows: for 78 K≤T≤383 K, C
p,m/J mol-1 K-1=19.086X
4+15.951X
3-5.2548X
2+90.192X+176.65, [X=(T-230.50/152.5)]. The thermodynamic functions on the base of the reference temperature of 298.15 K, {ΔH
T -ΔH
298.15} and {S
T-S
298.15}, were derived. Combustion energy of aspirin (Δc
U
m) was determined by static bomb combustion calorimeter. Enthalpy of combustion (Δc
H
o
m) and enthalpy of formation (Δf
H
o
m) were derived through Δc
U
m as - (3945.26±2.63) kJ mol-1 and - (736.41±1.30) kJ mol-1, respectively.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
7.
B. Tong Z. C. Tan J. N. Zhang S. X. Wang 《Journal of Thermal Analysis and Calorimetry》2009,95(2):469-475
The low-temperature heat capacity C
p,m of erythritol (C4H10O4, CAS 149-32-6) was precisely measured in the temperature range from 80 to 410 K by means of a small sample automated adiabatic
calorimeter. A solid-liquid phase transition was found at T=390.254 K from the experimental C
p-T curve. The molar enthalpy and entropy of this transition were determined to be 37.92±0.19 kJ mol−1 and 97.17±0.49 J K−1 mol−1, respectively. The thermodynamic functions [H
T-H
298.15] and [S
T-S
298.15], were derived from the heat capacity data in the temperature range of 80 to 410 K with an interval of 5 K. The standard
molar enthalpy of combustion and the standard molar enthalpy of formation of the compound have been determined: Δc
H
m0(C4H10O4, cr)= −2102.90±1.56 kJ mol−1 and Δf
H
m0(C4H10O4, cr)= − 900.29±0.84 kJ mol−1, by means of a precision oxygen-bomb combustion calorimeter at T=298.15 K. DSC and TG measurements were performed to study the thermostability of the compound. The results were in agreement
with those obtained from heat capacity measurements. 相似文献
8.
J. Leitner M. Hampl K. Růžička M. Straka D. Sedmidubský P. Svoboda 《Journal of Thermal Analysis and Calorimetry》2008,91(3):985-990
The heat capacity and the enthalpy increments of strontium metaniobate SrNb2O6 were measured by the relaxation method (2-276 K), micro DSC calorimetry (260-320 K) and drop calorimetry (723-1472 K). Temperature
dependence of the molar heat capacity in the form C
pm=(200.47±5.51)+(0.02937±0.0760)T-(3.4728±0.3115)·106/T
2 J K−1 mol−1 (298-1500 K) was derived by the least-squares method from the experimental data. Furthermore, the standard molar entropy
at 298.15 K S
m0 (298.15 K)=173.88±0.39 J K−1 mol−1 was evaluated from the low temperature heat capacity measurements. The standard enthalpy of formation Δf
H
0 (298.15 K)=-2826.78 kJ mol−1 was derived from total energies obtained by full potential LAPW electronic structure calculations within density functional
theory. 相似文献
9.
Elena Blanco J. M. Ruso J. Sabín G. Prieto F. Sarmiento 《Journal of Thermal Analysis and Calorimetry》2007,87(1):211-215
The interactions of lysozyme and myoglobin with anionic surfactants
(hydrogenated and fluorinated), at surfactant concentrations below the critical
micelle concentration, in aqueous solution were studied using spectroscopic
techniques. The temperature conformational transition of globular proteins
by anionic surfactants was analysed as a function of denaturant concentration
through absorbance measurements at 280 nm. Changes in absorbance of protein-surfactant
system with temperature were used to determine the unfolding thermodynamics
parameters, melting temperature, T
m,
enthalpy, ΔH
m,
entropy, ΔS
m
and the heat capacity change, ΔC
p,
between the native and denatured states. 相似文献
10.
Preparation and characterization of anion-cation surfactants modified montmorillonite 总被引:3,自引:2,他引:1
D. Chen J. X. Zhu P. Yuan S. J. Yang T. -H. Chen H. P. He 《Journal of Thermal Analysis and Calorimetry》2008,94(3):841-848
The low-temperature molar heat capacities of CoPc and CoTMPP were measured by temperature modulated differential scanning
calorimetry (TMDSC) over the temperature range from 223 to 413 K for the first time. No phase transition or thermal anomaly
was observed in the experimental temperature range for CoPc. However, a structural change was found to be nonreversible for
CoTMPP in the temperature range of 368–403 K, which was further validated by the results of IR and XRD. The molar enthalpy
ΔH
m and entropy ΔS
m of phase transition of the CoTMPP were determined to be 3.301 kJ mol−1 and 8.596 J K−1 mol−1, respectively. The thermodynamic parameters of CoPc and CoTMPP such as entropy and enthalpy relative to reference temperature
298.15 K were derived based on the above molar heat capacity data. Moreover, the thermal stability of these two compounds
was further investigated through TG measurements. Three steps of mass loss were observed in the TG curve for CoPc and five
steps for CoTMPP. 相似文献
11.
L. Peng X. Jiangjun M. Fangquan L. Xi Z. Chaocan 《Journal of Thermal Analysis and Calorimetry》2008,93(2):485-488
The standard molar enthalpy of combustion of cholesterol was measured at constant volume. According to value of Δr
U
mθ(−14358.4±20.65 kJ mol−1), Δr
H
mθ(−14385.7 kJ mol−1) of combustion reaction and Δf
H
mθ(2812.9 kJ mol−1) of cholesterol were obtained from the reaction equation. The enthalpy of combustion reaction of cholesterol was also estimated
by the average bond enthalpies. By design of a thermo-chemical recycle, the enthalpy of combustion of cholesterol were calculated
between 283.15∼373.15 K. Besides, molar enthalpy and entropy of fusion of cholesterol was obtained by DSC technique. 相似文献
12.
Magoshi J. Becker M. A. Han Z. Nakamura S. 《Journal of Thermal Analysis and Calorimetry》2002,68(3):833-839
The sample of LiCoO2 was synthesized, and the heat capacity was measured by adiabatic calorimetry between 13 and 300 K. The smoothed values of
the heat capacity were calculated from the data. The thermodynamic functions, standard enthalpy, entropy and Gibbs energy,
of LiCoO2 were calculated from the heat capacity and the numerical values are tabulated at selected temperatures from 15 to 300 K.
The heat capacity, enthalpy, entropy, and Gibbs energy at T=298.15 K are 71.57 J K–1mol–1, 9.853 kJ mol–1, 52.45 J K–1 mol–1, –5.786 kJ mol–1, respectively.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
13.
N. N. Smirnova T. A. Bykova N. A. Polotnyanko N. D. Shikina I. L. Khodakovskii 《Russian Journal of Physical Chemistry A, Focus on Chemistry》2010,84(11):1851-1855
The temperature dependence of the heat capacity C
p
o = f(T) of palladium oxide PdO(cr.) was studied for the first time in an adiabatic vacuum calorimeter in the range of 6.48–328.86
K. Standard thermodynamic functions C
p
o(T), H
o(T) — H
o(0), S
o(T), and G
o(T) — H
o(0) in the range of T → 0 to 330 K (key quantities in different thermodynamic calculations with the participation of palladium compounds) were
calculated on the basis of the experimental data. Based on an analysis of studies on determining the thermodynamic properties
of PdO(cr.), the following values of absolute entropy, standard enthalpy, and Gibbs function of the formation of palladium
oxide are recommended: S
o(298.15) = 39.58 ± 0.15 J/(K mol), Δf
H
o(298.15) = −112.69 ± 0.32 kJ/mol, Δf
G
o(298.15) = −82.68 ± 0.35 kJ/mol. The stability of Pd(OH)2 (amorph.) with respect to PdO(cr.) was estimated. 相似文献
14.
N. N. Smirnova T. A. Bykova V. N. Larina T. G. Kulagina A. D. Pomogailo G. I. Dzhardimalieva 《Polymer Science Series A》2010,52(4):349-355
The temperature dependences of the heat capacities of hydrated acrylamide and poly(acrylamide) complexes of cobalt nitrate
are studied via high-precision adiabatic calorimetry at 6 to 300–380 K. The energy of combustion is estimated via isothermic
calorimetry. This evidence makes it possible to calculate thermodynamic functions C
p
ℴ(T), H
ℴ(T) − H
ℴ(0), S
ℴ(T), G
ℴ(T) − H
ℴ(0) at 0 to 300–380 K; the standard enthalpy of combustion, ΔcH
ℴ; and the thermodynamic parameters of formation, Δ
f
H
ℴ, Δ
f
S
ℴ, and Δ
f
G
ℴ, of monomer and polymer complexes composed of simple compounds at 298.15 K. The results are used for the estimation of enthalpy
Δpol
H
ℴ, entropy Δpol
S
ℴ, and Gibbs function Δpol
G
ℴ of bulk polymerization for hydrated acrylamide complexes of cobalt nitrate at 0–300 K. 相似文献
15.
The temperature dependence of the Gibbs free energy difference (ΔG), enthalpy difference (ΔH) and entropy difference (ΔS) between the undercooled meltand the corresponding equilibrium solid has been analysed for glass forming polymeric materials
by calculating ΔG, ΔH and ΔS within the framework of the hole theory of liquids. The study is made for nine samples of glass forming polymeric melts;
polypropylene oxide (PPO), polyamid-6 (PA-6), polytetramethylene oxide (PTMO), polyethylene oxide (PEO), polystyrene (PS),
polypropylene (PP), polyethylene (PE), polyethylene terephthalate (PET) and polybutadiene (PB) and three simple organic liquids:
tri-α-naphthyl benzene (tri-α-NB), o-terphenyl (o-ter) and phenyl salicylate (salol) in the entire temperature range T
m (melting temperature) to T
g (glass transition temperature). The ideal glass transition temperature (T
K) and the residual entropy (ΔS
R) of these samples have also been studied due to their important role in the study of the glass forming ability of materials.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
16.
G. I. Zharkova S. V. Sysoev P. A. Stabnikov V. A. Logvinenko I. K. Igumenov 《Journal of Thermal Analysis and Calorimetry》2011,103(1):381-385
Volatile palladium(II) β-iminoketonates of the general formula Pd(R–C(NH)–CH–CO–R1),where R and R1 are CH3, CF3, C(CH3)3 in various combinations, were synthesized and identified. Thermal properties of the resulting palladium(II) complexes in
the solid phase were studied by thermogravimetric analysis under an argon atmosphere. The temperature dependence of the saturated
vapor pressure was measured for the compounds by the flow method and thermodynamic characteristics of vaporization processes,
enthalpy ΔH
T and entropy ΔS
To, were determined. The atom-atomic potential calculation of the van der Waals energy (E
cryst) of the crystal lattice was performed and the results were compared to the experimental values of the sublimation enthalpy
for the complexes under study. 相似文献
17.
T. R. Usacheva V. A. Sharnin E. Matteoli 《Russian Journal of Physical Chemistry A, Focus on Chemistry》2011,85(11):1898-1902
Complexation of the 18-crown-6 ether (18C6) with glycine (Gly) in mixed H2O-DMSO solvents with the composition of 0.1, 0.2, and 0.25 mole fraction of DMSO (T = 298.15 K) was studied calorimetrically. Thermodynamic characteristics of the reaction of the formation of the molecular
Gly18C6 complex (Δr
G°, Δr
H°, TΔr
S°) were calculated from the calorimetric data. It was established that the change in the stability of the Gly18C6 complex
is mainly determined by the predominance of the enthalpy component of the Gibbs energy over the entropy component. It was
shown during the analysis of the enthalpy contributions of the reagents to the enthalpy of the reaction of the formation of
Gly18C6 that the change in the enthalpy of the reaction upon a change the solvent composition was due to changes in the solvation
state of 18C6. 相似文献
18.
Galán J. J. González-Pérez A. Rodríguez J. R. 《Journal of Thermal Analysis and Calorimetry》2003,72(2):465-470
Specific conductivity of aqueous solutions of dodecyldimethylethylammonium bromide has been determined in the temperature
range of 15-40°C. The critical micelle concentration (cmc) and ionization degree of the micelles, b, were determined from
the data. Thermodynamic functions, such as standard Gibbs free energy, ΔG
m°, enthalpy, ΔG
m°, and entropy, ΔG
m°, of micellization, were estimated by assuming that the system conforms to the mass action model. The change in heat capacity
upon micellization, ΔG
m°, was estimated from the temperature dependence of ΔG
m°. An enthalpy-entropy compensation phenomenom for the studied system has been found.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
19.
Mario N. Berberan-Santos Evgeny N. Bodunov Lionello Pogliani 《Journal of mathematical chemistry》2008,43(4):1437-1457
The thermodynamic properties, enthalpy of vaporization, entropy, Helmholtz function, Gibbs function, but especially the heat
capacity at constant volume of a van der Waals gas (and liquid) at the phase transition are examined in two different limit
approximations. The first limit approximation is at the near-critical temperatures, i.e., for T/T
c
→ 1, where T
c
is the critical temperature, the other limit approximation is at the near-zero temperatures, T→ 0. In these limits, the analytical equations for liquid and gas concentrations at saturated conditions were obtained. Although
the heat capacities at constant volume of a van der Waals gas and liquid do not depend on the volume, they have different
values and their change during the phase transition was calculated. It should be noticed that for real substances the equations
obtained at the near-zero temperature are only valid for T > T
triple point and T ≪ T
c
, which means that found equations can be used only for substances with T
triple point ≪ T
c
. 相似文献
20.
Z. H. Zhang L. X. Sun Z. C. Tan F. Xu X. C. Lv J. L. Zeng Y. Sawada 《Journal of Thermal Analysis and Calorimetry》2007,89(1):289-294
The molar heat capacities of the room temperature ionic liquid 1-butylpyridinium tetrafluoroborate (BPBF4) were measured by an adiabatic calorimeter in temperature range from 80 to 390 K. The dependence of the molar heat capacity
on temperature is given as a function of the reduced temperature X by polynomial equations, C
p,m [J K−1 mol−1]=181.43+51.297X −4.7816X
2−1.9734X
3+8.1048X
4+11.108X
5 [X=(T−135)/55] for the solid phase (80–190 K), C
p,m [J K−1 mol−1]= 349.96+25.106X+9.1320X
2+19.368X
3+2.23X
4−8.8201X
5 [X=(T−225)/27] for the glass state (198–252 K), and C
p,m[J K−1 mol−1]= 402.40+21.982X−3.0304X
2+3.6514X
3+3.4585X
4 [X=(T−338)/52] for the liquid phase (286–390 K), respectively. According to the polynomial equations and thermodynamic relationship,
the values of thermodynamic function of the BPBF4 relative to 298.15 K were calculated in temperature range from 80 to 390 K with an interval of 5 K. The glass transition
of BPBF4 was observed at 194.09 K, the enthalpy and entropy of the glass transition were determined to be ΔH
g=2.157 kJ mol−1 and ΔS
g=11.12 J K−1 mol−1, respectively. The result showed that the melting point of the BPBF4 is 279.79 K, the enthalpy and entropy of phase transition were calculated to be ΔH
m = 8.453 kJ mol−1 and ΔS
m=30.21 J K−1 mol−1. Using oxygen-bomb combustion calorimeter, the molar enthalpy of combustion of BPBF4 was determined to be Δc
H
m0 = −5451±3 kJ mol−1. The standard molar enthalpy of formation of BPBF4 was evaluated to be Δf
H
m0 = −1356.3±0.8 kJ mol−1 at T=298.150±0.001 K. 相似文献