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1.
Pascale Bénézeth Donald A. Palmer David J. Wesolowski 《Journal of solution chemistry》1997,26(1):63-84
The three molal dissociation quotients for citric acid were measured potentiometrically with a hydrogen-electrode concentration
cell from 5 to 150°C in NaCl solutions at ionic strengths of 0.1, 0.3, 0.6, and 1 molal. The molal dissociation quotients
and available literature data at infinite dilution were fitted by empirical equations in the all-anionic form involving an
extended Debye-Hückel term and up to five adjustable parameters involving functions of temperature and ionic strength. This
treatment yielded the following thermodynamic quantitites for the first dissociation equilibrium at 25°C: logK
1a=−3.127±0.002, ΔH
1a
o
=4.1±0.2 kJ-mol−1, ΔS
1a
o
=−46.3±0.7 J-K−1-mol−1, and ΔCp
1a
o
=−162±7 J-K−1-mol−1; for the second acid dissociation equilibrium at 25°C: logK
2a
=−4.759±0.001, ΔH
2a
o
=2.2±0.1, ΔS
2a
o
=−83.8±0.4, and ΔCp
2a
o
=−192±15, and for the third dissociation equilibrium at 25°C: logK
3a=−6.397±0.002, ΔH
3a
o
=−3.6±0.2, ΔS
3a
o
=−134.5±0.7, and ΔCp
3a
o
=−231±7. 相似文献
2.
Lebedev B. V. Bykova T. A. Lobach A. S. 《Journal of Thermal Analysis and Calorimetry》2000,62(1):257-265
The temperature dependence of the molar heat capacity (C0
p) of hydrofullerene C60H36 between 5 and 340 K was determined by adiabatic vacuum calorimetry with an error of about 0.2%. The experimental data were
used for the calculation of the thermodynamic functions of the compound in the range 0 to340 K. It was found that at T=298.15 K and p=101.325 kPa C0
p (298.15)=690.0 J K−1 mol−1,Ho(298.15)−Ho(0)= 84.94 kJ mol−1,So(298.15)=506.8 J K−1 mol−1, Go(298.15)−Ho(0)= −66.17 kJ mol−1. The standard entropy of formation of hydrofullerene C60H36 and the entropy of reaction of its formation by hydrogenation of fullerene C60 with hydrogen were estimated and at T=298.15 K they were ΔfSo= −2188.4 J K−1 mol−1 and ΔrSo= −2270.5 J K−1mol−1, respectively.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
3.
The temperature dependence of heat capacity of C70 fullerene was studied by calorimetry in the range between 6 and 390 K. Phase transitions were established and their thermodynamic
characteristics were determined. From the experimental data obtained, the thermodynamic functionsH
o
(T)-H
o(0),S
o(T),G
o(T)-H
o(0) for temperatures between 0 and 390 K were calculated. The results were used to calculate the standard values of Δf
S
o, Δf
G
o, and logK
f
o
for the formation of C70 from graphite.
Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 4, pp. 647–650, April, 1998. 相似文献
4.
N. B. Morozova P. P. Semyannikov S. V. Sysoev V. M. Grankin I. K. Igumenov 《Journal of Thermal Analysis and Calorimetry》2000,60(2):489-495
The temperature dependency of the saturated vapor pressure of Ir(acac)3 has been measured by the method of calibrated volume (MCV), the Knudsen method, the flow transpiration method, and the membrane
method. The thermodynamic parameters of phase transition of a crystal to gas were calculated using each of these methods,
and the following values of ΔH
T
0 (kJ mol−1) and ΔS
T
0 (J mol−1K−1), respectively, were obtained: MCV: 101.59, 156.70; Knudsen: 130.54, 224.40; Flow transpiration: 129.34, 212.23; Membrane:
95.45, 149.44
Coprocessing of obtaining data (MCV, flow transportation method and Knudsen method) at temperature ranges 110−200°C as also
conducted:ΔH
T
0 =127.9±2.1 (kJ mol−1 ); ΔS
T
0 =215.2±5.0 (J mol−1 K−1 ).
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
5.
Polymorphism of paracetamol 总被引:1,自引:0,他引:1
G. L. Perlovich Tatyana V. Volkova Annette Bauer-Brandl 《Journal of Thermal Analysis and Calorimetry》2007,89(3):767-774
The thermodynamic relationship between crystal modifications of paracetamol was studied by alternative methods. Temperature
dependence of saturated vapor pressure for polymorphic modifications of the drug paracetamol (acetaminophen) was mea sured
and thermodynamic functions of the sublimation process calculated. Solution calorimetry was carried out for the two modifications
in the same solvent. Thermodynamic parameters for sublimation for form I (monoclinic) were found: ΔG
sub298=60.0 kJ mol−1; ΔH
sub298=117.9±0.7 kJ mol−1; ΔS
sub298=190±2 J mol−1 K−1. For the orthorhombic modification (form II), the saturated vapor pressure could only be studied at 391 K. Phase transition
enthalpy at 298 K, ΔH
tr298(I→II)=2.0±0.4 kJ mol−1, was derived as the difference between the solution enthalpies of the noted polymorphs in the same solution (methanol). Based
on ΔH
tr298 (I→II), differences between temperature dependencies of heat capacities of both modifications and the vapor pressure value
of form II at 391 K, the temperature dependence of saturated vapor pressure and thermodynamic sublimation parameters for modification
II were also estimated (ΔG
sub298=56.1 kJ mol−1; ΔH
sub298=115.9±0.9 kJ mol−1; ΔS
sub298=200±3 J mol−1 K−1). The results indicate that the modifications are monotropically related, which is in contrast to findings recently reported
found by classical thermochemical methods. 相似文献
6.
Deprotonation constants of phthalic (H2A) and biphthalic (HA−) acids and of mono-protonated (BH+) and di-protonated (BH22+) piperazine acids have been determined at 25 °C by measuring the Emf of galvanic cells comprising H+-sensitive glass GE(H+) and Ag,AgCl electrodes in non-aqueous isodielectric mixtures of protic ethylene glycol (EG) and dipolar aprotic N,N-dimethylformamide
(DMF). Solvent effects on deprotonation of the acids: ∂(ΔG
disso)=2.303RT[p(s
K
a)−p(R
K
a)], have been dissected into transfer Gibbs energies, ΔG
to
, of the species involved by evaluating ΔG
to of the uncharged phthalic acid and base piperazine (B) from the measured solubilities of the acid and base, respectively,
and using ΔG
to of H+ based on the TATB reference electrolyte assumptions, as evaluated earlier. The contributions of the different species involved
in the protolytic equilibria i.e., H+,H2A,HA−,BH22+ and BH+ and their respective conjugate bases HA−,A2−,BH+ and B have been discussed in terms of their solvation behavior as guided by the ‘acid-base’, dispersion, structural and electronic
characteristics of the acid-base species and of the co-solvent molecules and binary mixtures, ignoring the Born-type electrostatic
interactions on the ionic species as the solvent system is quasi isodielectric. 相似文献
7.
Thermal behavior of 1,2,3-triazole nitrate 总被引:1,自引:0,他引:1
Liang Xue Feng-Qi Zhao Xiao-Ling Xing Zhi-Ming Zhou Kai Wang Hong-Xu Gao Jian-Hua Yi Si-Yu Xu Rong-Zu Hu 《Journal of Thermal Analysis and Calorimetry》2011,104(3):999-1004
The thermal decomposition behaviors of 1,2,3-triazole nitrate were studied using a Calvet Microcalorimeter at four different
heating rates. Its apparent activation energy and pre-exponential factor of exothermic decomposition reaction are 133.77 kJ mol−1 and 1014.58 s−1, respectively. The critical temperature of thermal explosion is 374.97 K. The entropy of activation (ΔS
≠), the enthalpy of activation (ΔH
≠), and the free energy of activation (ΔG
≠) of the decomposition reaction are 23.88 J mol−1 K−1, 130.62 kJ mol−1, and 121.55 kJ mol−1, respectively. The self-accelerating decomposition temperature (T
SADT) is 368.65 K. The specific heat capacity was determined by a Micro-DSC method and a theoretical calculation method. Specific
heat capacity equation is
C\textp ( \textJ mol - 1 \text K - 1 ) = - 42.6218 + 0.6807T C_{\text{p}} \left( {{\text{J mol}}^{ - 1} {\text{ K}}^{ - 1} } \right) = - 42.6218 + 0.6807T (283.1 K < T < 353.2 K). The adiabatic time-to-explosion is calculated to be a certain value between 98.82 and 100.00 s. The critical
temperature of hot-spot initiation is 637.14 K, and the characteristic drop height of impact sensitivity (H
50) is 9.16 cm. 相似文献
8.
Helena Dodziuk Anna Bielejewska Wojciech Schilf Haruhisa Ueda 《Central European Journal of Chemistry》2011,9(6):1056-1061
The NMR spectra of [2.2]paracyclophane with β- or γ-cyclodextrin in DMF-d7 at room temperature do not show significant complexation, while HPLC of the complexes in mixed H2O:alcohol solvents demonstrate complexation with different stoichiometries. At 243 K in DMF solution the H3 and H5 NMR signals
of γ-cyclodextrin (but not β) exhibit complexation-induced chemical shifts denoting complex formation. According to HPLC,
at room temperature the [2.2]paracyclophane complex with β-cyclodextrin in 20% H2O:EtOH exhibits 1:2 stoichiometry with K
1 = 1×102 ± 2, K
2 = 9.0×104 ± 2×103 (K = 9×106) while that with γ-cyclodextrin in 50% H2O:MeOH exhibits 1:1 stoichiometry with K
1 = 4×103 ± 150 M−1. Thermodynamic parameters for both complexes have been estimated from the retention time temperature dependence. For the
β-cyclodextrin complexation at 25°C ΔG
0
CD is −39.7 kJ mol−1 while ΔH
0
CD and ΔS
0
CD are −88.2 kJ mol−1 and −0.16 kJ mol−1 K−1. For γ-cyclodextrin, the corresponding values are ΔG
0
CD = −20.5 kJ mol−1, ΔH
0
CD = −33.5 kJ mol−1 and ΔS
0
CD = −0.04 kJ mol−1 K−1.
相似文献
9.
T. G. Kulagina Ya. S. Samosudova I. A. Letyanina E. V. Sevast’yanov N. N. Smirnova L. A. Smirnova A. E. Mochalova 《Russian Journal of Physical Chemistry A, Focus on Chemistry》2012,86(5):747-751
The temperature dependence of the heat capacity C
p
o= f(T) 2 of 2-ethylhexyl acrylate was studied in an adiabatic vacuum calorimeter over the temperature range 6–350 K. Measurement
errors were mainly of 0.2%. Glass formation and vitreous state parameters were determined. An isothermic shell calorimeter
with a static bomb was used to measure the energy of combustion of 2-ethylhexyl acrylate. The experimental data were used
to calculate the standard thermodynamic functions C
p
o(T), H
o(T)-H
o(0), S
o(T)-S
o(0), and G
o(T)-H
o(0) of the compound in the vitreous and liquid states over the temperature range from T → 0 to 350 K, the standard enthalpies of combustion Δc
H
o, and the thermodynamic characteristics of formation Δf
H
o, Δf
S
o, and Δf
G
o at 298.15 K and p = 0.1 MPa. 相似文献
10.
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
11.
A. V. Markin N. N. Smirnova I. E. Boronina V. A. Ruchenin A. G. Lyapin 《Russian Chemical Bulletin》2008,57(9):1975-1980
Temperature dependences of the heat capacities of disordered graphite-like nanostructures prepared by the thermobaric treatment
of fullerite C60 (p = 2 and 8 GPa, T = 1373 K) were measured in the temperature ranges from 7 to 360 K in an adiabatic vacuum calorimeter and from 330 to 650
K in a differential scanning calorimeter. At T < 50 K, the dependences obtained were analyzed using the Debye theory of the heat capacity of solids and its multifractal
version. The fractal dimensions D were determined and some conclusions on the heterodynamic character of the structures studied were made. The thermodynamic
functions C
p
o
T), H
o(T) − H
o(0), S
o(T) − S
o(0), and G
o(T) − H
o(0) were calculated in the temperature range from T → 0 to 610 (650) K. The thermodynamic properties of the graphite-like nanostructures studied and some carbon allotropes were
compared. The standard entropies of formation Δf
S
o of the graphite nanostructures studied and diamond were calculated along with the standard entropies of the reactions of
their synthesis from the face-centered cubic phase of fullerite C60 and their interconversions at T = 298.15 K.
Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 9, pp. 1940–1945, September, 2008. 相似文献
12.
H. X. Ma B. Yan Y. H. Ren Y. Hu Y. L. Guan F. Q. Zhao J. R. Song R. Z. Hu 《Journal of Thermal Analysis and Calorimetry》2011,103(2):569-575
3,3-Dinitroazetidinium (DNAZ) salt of perchloric acid (DNAZ·HClO4) was prepared, it was characterized by the elemental analysis, IR, NMR, and a X-ray diffractometer. The thermal behavior
and decomposition reaction kinetics of DNAZ·HClO4 were investigated under a non-isothermal condition by DSC and TG/DTG techniques. The results show that the thermal decomposition
process of DNAZ·HClO4 has two mass loss stages. The kinetic model function in differential form, the value of apparent activation energy (E
a) and pre-exponential factor (A) of the exothermic decomposition reaction of DNAZ·HClO4 are f(α) = (1 − α)−1/2, 156.47 kJ mol−1, and 1015.12 s−1, respectively. The critical temperature of thermal explosion is 188.5 °C. The values of ΔS
≠, ΔH
≠, and ΔG
≠of this reaction are 42.26 J mol−1 K−1, 154.44 kJ mol−1, and 135.42 kJ mol−1, respectively. The specific heat capacity of DNAZ·HClO4 was determined with a continuous C
p mode of microcalorimeter. Using the relationship between C
p and T and the thermal decomposition parameters, the time of the thermal decomposition from initiation to thermal explosion (adiabatic
time-to-explosion) was evaluated as 14.2 s. 相似文献
13.
R. Donat G. K. Cılgı S. Aytas H. Cetisli 《Journal of Radioanalytical and Nuclear Chemistry》2009,279(1):271-280
This paper discusses the sorption properties for U(VI) by alginate coated CaSO4·2H2O sepiolite and calcined diatomite earth (Kieselguhr) (ACSD). The removal of U(VI) from aqueous solution by sorption onto
ACSF in a single component system with various contact times, pH, temperatures, and initial concentrations of U(VI) was investigated.
The sorption patterns of uranium on the composite adsorbent followed the Langmuir, Freundlich and Dubinin-Radushkhevic (D-R)
isotherms. The Freundlich, Langmuir, and D-R models have been applied and the data correlated well with Freundlich model and
that the sorption was physical in nature (sorption energy, E
a
= 17.05 kJ/mol). The thermodynamic parameters such as variation of enthalpy ΔH, variation of entropy ΔS and variation of Gibbs free energy ΔG were calculated from the slope and intercept of lnK
0 vs. 1/T plots. Thermodynamic parameters (ΔH
ads = 31.83 kJ/mol, ΔS
ads = 167 J/mol·K, ΔG
o
ads (293.15 K) = −17.94 kJ/mol) showed the endothermic heat of sorption and the feasibility of the process. The thermodynamics
of U(VI) ion/ACSD system indicates the spontaneous and endothermic nature of the process. It was noted that an increase in
temperature resulted in a higher uranium loading per unit weight of the adsorbent. 相似文献
14.
Letícia R. Teixeira Rubén D. Sinisterra Rafael P. Vieira Aline Scarlatelli-Lima Márcio F.D. Moraes Maria Carolina Doretto Ângelo M. Denadai Heloisa Beraldo 《Journal of inclusion phenomena and macrocyclic chemistry》2006,54(1-2):133-138
A non-hygroscopic pharmaceutical composition was obtained following a host-guest strategy that used the anticonvulsant drug
sodium valproate (VA) and α-cyclodextrin. The pharmaceutical composition was fully characterized by thermal analyses (TG/DTG,
DSC), X-ray powder diffraction and by 1H, 13C, hydrogen relaxation times (T1) and 2D-ROESY NMR techniques. Isothermal titration calorimetry (ITC) was used to determine the VA:α-CD 1:1 stoichiometry
as well as to calculate the equilibrium constant (K) and thermodynamic energies of interaction (ΔGo, ΔHo and TΔSo). 相似文献
15.
Hong-Lin Zhang Zhe Kong Yong-Mei Yan Gan-Zuo Li Li Yu Fei Geng 《Journal of solution chemistry》2008,37(12):1631-1644
The power-time curves for the micelle formation process were determined for two anionic surfactants, sodium laurate (SLA)
and sodium dodecyl sulfate (SDS), in mixed alcohol + N,N-dimethylacetamide (DMA) solvent using titration microcalorimetry.
From the data of the lowest point and the area of the power-time curves, their critical micelle concentration (CMC) and ΔH
mo were obtained. The other thermodynamic functions of the micellization process (ΔG
mo and ΔS
mo) were also calculated with thermodynamic equations. For both surfactants, the effects of the carbon number (chain length)
of the alcohol, the concentration of alcohol, and the temperature on the CMC and thermodynamic functions are discussed. For
systems containing identical concentrations of a different alcohol, values of the CMC, ΔH
mo and ΔS
mo increased whereas ΔG
mo decreased with increasing temperature. For systems containing an identical alcohol concentration at the same temperature,
values of the CMC, ΔH
mo,ΔG
mo and ΔS
mo decrease with increasing carbon number of alcohol. For systems containing the same alcohol at the same temperature, the CMC
and ΔG
mo values increase whereas ΔH
mo and ΔS
mo decrease with increasing alcohol concentration. 相似文献
16.
Rearrangements of cyclopentadienyl cyanates,isocyanates and their thio-,seleno-, and telluro-analogs
Dushenko G. A. Mikhailova O. I. Mikhailov I. E. Minyaev R. M. Minkin V. I. 《Russian Chemical Bulletin》2009,58(8):1713-1723
Dynamic NMR spectroscopy revealed that pentaphenylcyclopentadienyl isoselenocyanate undergoes reversible hetero-Cope rearrangement
(ΔG
≠
408 K ∼ 22 kcal mol−1, C6D5CD3) giving isomeric selenocyanate in which 1,5-sigmatropic shifts of the SeCN group along the perimeter of the cyclopentadiene
ring occur (ΔG
≠
298 K = 16.7 kcal mol−1, C6D5CD3). On the contrary, pentaphenylcyclopentadienyl iso(thio)cyanates Ph5C5NCO and Ph5C5NCS are structurally rigid compounds on the NMR time scale. The energy barrier to the 3,3-shift of the isoselenocyanate group
in pentaphenylcyclopentadienyl derivative Ph5C5NCSe (ΔG
298 K
≠ = 17.9 kcal mol−1) caclulated using the B3LYP/6-31G** method is 7.6 kcal mol−1 lower than for the unsubstituted analog H5C5NCSe. 相似文献
17.
The protonation equilibria for some phenolic acids in nonaqueous solutions have been studied by pH-potentiometry. The dissociation
constants, pK
a, of these phenolic acids and the thermodynamic functions, ΔG
o,ΔH
o and ΔS
o, for the successive and overall protonation processes of these phenolic acids have been derived at different temperatures
in three different mixtures of water and dioxane (mole fractions of dioxane were 0.083, 0.174 and 0.33). Titrations were also
carried out in (water + dioxane) with ionic strengths of 0.15, 0.20 and 0.25 mol⋅dm−3 NaNO3, and the resulting dissociation constants are reported. A detailed thermodynamic analysis of the effects of organic solvent,
dioxane, temperature and ionic strength on the protonation processes of phenolic acids is presented and discussed to determine
the factors which control these processes.
Ahmed E. Fazary; previous address: Egyptian Organization for Biological Products and Vaccines, 51 Wezaret El-Zeraa Street,
Agouza, Giza, Egypt. Tel. +2010-3017357. 相似文献
18.
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
19.
I. E. Paukov Yulia A. Kovalevskaya Elena V. Boldyreva 《Journal of Thermal Analysis and Calorimetry》2008,93(2):423-428
Heat capacity C
p(T) of the orthorhombic polymorph of L-cysteine was measured in the temperature range 6–300 K by adiabatic calorimetry; thermodynamic functions were calculated
based on these measurements. At 298.15 K the values of heat capacity, C
p; entropy, S
m0(T)-S
m0(0); difference in the enthalpy, H
m0(T)-H
m0(0), are equal, respectively, to 144.6±0.3 J K−1 mol−1, 169.0±0.4 J K−1 mol−1 and 24960±50 J mol−1. An anomaly of heat capacity near 70 K was registered as a small, 3–5% height, diffuse ‘jump’ accompanied by the substantial
increase in the thermal relaxation time. The shape of the anomaly is sensitive to thermal pre-history of the sample. 相似文献
20.
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