共查询到20条相似文献,搜索用时 31 毫秒
1.
1. Results of thermodynamic and kinetic investigations for the different crystalline calcium carbonate phases and their phase
transition data are reported and summarized (vaterite: V; aragonite: A; calcite: C). A→C: T
tr=455±10°C, Δtr
H=403±8 J mol–1 at T
tr, V→C: T
tr=320–460°C, depending on the way of preparation,Δtr
H=–3.2±0.1 kJ mol–1 at T
tr,Δtr
H=–3.4±0.9 kJ mol–1 at 40°C, S
V
Θ= 93.6±0.5 J (K mol)–1, A→C: E
A=370±10 kJ mol–1; XRD only, V→C: E
A=250±10 kJ mol–1; thermally activated, iso- and non-isothermal, XRD
2. Preliminary results on the preparation and investigation of inhibitor-free non-crystalline calcium carbonate (NCC) are
presented. NCC→C: T
tr=276±10°C,Δtr
H=–15.0±3 kJ mol–1 at T
tr, T
tr – transition temperature, Δtr
H – transition enthalpy, S
Θ – standard entropy, E
A – activation energy.
3. Biologically formed internal shell of Sepia officinalis seems to be composed of ca 96% aragonite and 4% non-crystalline calcium carbonate.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
2.
G. Xie S. P. Chen S. L. Gao X. X. Meng Q. Z. Shi 《Journal of Thermal Analysis and Calorimetry》2006,83(3):693-700
A novel solid complex, formulated as Ho(PDC)3
(o-phen), has been obtained from the reaction
of hydrate holmium chloride, ammonium pyrrolidinedithiocarbamate (APDC) and
1,10-phenanthroline (o-phen·H2O)
in absolute ethanol, which was characterized by elemental analysis, TG-DTG
and IR spectrum. The enthalpy change of the reaction of complex formation
from a solution of the reagents, ΔrHmθ (sol), and the molar heat capacity of the complex, cm,
were determined as being –19.161±0.051 kJ mol–1
and 79.264±1.218 J mol–1 K–1
at 298.15 K by using an RD-496 III heat conduction microcalorimeter. The enthalpy
change of complex formation from the reaction of the reagents in the solid
phase, ΔrHmθ(s), was calculated as
being (23.981±0.339) kJ mol–1 on the
basis of an appropriate thermochemical cycle and other auxiliary thermodynamic
data. The thermodynamics of reaction of formation of the complex was investigated
by the reaction in solution at the temperature range of 292.15–301.15
K. The constant-volume combustion energy of the complex, ΔcU, was determined as being –16788.46±7.74
kJ mol–1 by an RBC-II type rotating-bomb
calorimeter at 298.15 K. Its standard enthalpy of combustion, ΔcHmθ, and standard enthalpy of formation,
ΔfHmθ, were calculated to be –16803.95±7.74 and –1115.42±8.94
kJ mol–1, respectively. 相似文献
3.
Z. Fengqi G. Hongxu L. Yang H. Rongzu C. Pei G. Sheng-li Y. Xu-wu S. Qizhen 《Journal of Thermal Analysis and Calorimetry》2006,85(3):791-794
The constant-volume combustion energies of
the lead salts of 2-hydroxy-3,5-dinitropyridine (2HDNPPb) and 4-hydroxy-3,5-dinitropyridine
(4HDNPPb), ΔU
c
(2HDNPPb(s) and 4HDNPP(s)),
were determined as –4441.92±2.43 and –4515.74±1.92
kJ mol–1 , respectively, at 298.15 K. Their
standard enthalpies of combustion, Δc
m
H θ(2HDNPPb(s) and 4HDNPPb(s), 298.15 K), and standard enthalpies of formation,
Δr
m H θ(2HDNPPb(s) and 4HDNPPb(s),
298.15 K) were as –4425.81±2.43, –4499.63±1.92 kJ
mol–1 and –870.43±2.76, –796.65±2.32
kJ mol–1 , respectively. As two combustion
catalysts, 2HDNPPb and 4HDNPPb can enhance the burning rate and reduce the
pressure exponent of RDX–CMDB propellant. 相似文献
4.
L. A. C. Leiva J. M. Romero N. L. Jorge L. F. R. Cafferata M. E. Gómez Vara E. A. Castro 《Chemistry of Heterocyclic Compounds》2009,45(12):1455-1459
The thermal decomposition study of 3,3,6,6-tetramethyl-1,2,4,5-tetroxane (acetone cyclic diperoxide) was carried out in 2-methoxyethanol
solution in the 130-166 °C temperature range. The overall reaction follows a first-order kinetic law up to at least 75% diperoxide
conversion. The activation parameters (ΔH# = 22.5 ± 0.7 kcal⋅mol–1 and ΔS# = -25.6 ± 0.5 cal⋅mol–1⋅K–1) for the unimolecular rupture of the O–O bond in the diperoxide molecule were obtained by measuring the remnant diperoxide
at different reaction times by the CG technique. Acetone was detected by GC as the major organic product of the reaction. 相似文献
5.
Thermochemical
studies on the thioproline 总被引:3,自引:0,他引:3
The combustion energy of thioproline was determined
by the precision rotating-bomb calorimeter at 298.15 K to be Δc
U= –2469.30±1.44 kJ mol–1.
From the results and other auxiliary quantities, the standard molar enthalpy
of combustion and the standard molar enthalpy of formation of thioproline
were calculated to be Δc
H
m
θC4H7NO2S,
(s), 298.15 K= –2469.92±1.44 kJ mol–1
and Δf
H
m
θC4H7NO2S, (s), 298.15K= –401.33±1.54
kJ mol–1. 相似文献
6.
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
7.
S. Vecchio 《Journal of Thermal Analysis and Calorimetry》2006,84(1):271-278
The standard sublimation enthalpies of (2,4,5-trichlorophenoxy)acetonitrile
and (2,4,5-trichlorophenoxy)aniline were determined by isothermal thermogravimetry
using the Langmuir equation and by non-isothermal differential scanning calorimetry
for comparison. The used procedure was previously tested using three reference
compounds: benzoic acid, succinic acid and salicylic acid. The results compared
to those reported in literature show an excellent agreement for two of the
three compounds while the third agrees quite well. For (2,4,5-trichlorophenoxy)acetonitrile
and (2,4,5-trichlorophenoxy)aniline, the extrapolation of data at 298.15 K
were obtained, respectively: ΔsubH°(298
K)={(106±4) and (101±4)} kJ mol–1.
From Clausius Clapeyron equation obtained after the determination of the vaporization
constant α′, the following standard sublimation entropies for
(2,4,5-trichlorophenoxy)acetonitrile and (2,4,5-trichlorophenoxy)aniline equal
to ΔsubS°(298
K)=(251 and 237) J K–1 mol–1,
respectively, were derived, with an error of ±4 J K–1
mol–1 equal for the studied herbicides. 相似文献
8.
S. Vecchio 《Journal of Thermal Analysis and Calorimetry》2007,87(1):79-83
The vaporization enthalpies of two acetanilide pesticides, alachlor
(2’,6’-diethyl-N-(methoxymethyl)-2-chloroacetanilide) and metolachlor
(2-chloro-N-(2-ethyl-6-methylphenyl)-N-[(1S)-2-methoxy-1-methylethyl] acetamide),
were determined by processing non-isothermal thermogravimetry data according
to the Clausius-Clapeyron equation. The reliability of the procedure proposed
was tested carrying out some experiments at different heating rates using
acetanilide as a reference compound. A good agreement is found among the vaporization
enthalpies derived from all the multi-heating rate experiments as well as
with the one predicted from the vapor pressure data taken from literature.
The vaporization temperatures (T
vap=470±2
K and T
vap=479±2
K) and enthalpies (Δvap
H°(436
K)=85±1 kJ mol–1 and Δvap
H°(436 K)=70±1 kJ mol–1)
for alachlor and metolachlor, were selected, respectively. 相似文献
9.
Tandra?Das Biplab?K.?Bera Subhasis?Mallick Parnajyoti?Karmakar Arup?Mandal Subala?Mondal Gauri?S.?De Alak?K.?Ghosh 《Transition Metal Chemistry》2010,35(7):885-890
The interaction of thiosemicarbazide with the title complex has been studied spectrophotometrically in aqueous medium as a
function of [complex], [thiosemicarbazide], pH and temperature at constant ionic strength. At pH 7.4, the reaction shows two
distinct paths; both of which are [thiosemicarbazide] dependent. A parallel reaction scheme fits well with the experimental
findings. An associative interchange mechanism is proposed for both the paths; the activation parameters calculated from Eyring
plots are ΔH1≠ = 14.2 ± 0.8 kJ mol−1, ΔS1≠ = −241 ± 2 JK−1 mol−1, ΔH2≠ = 30.8 ± 1.4 kJ mol−1 and ΔS2≠ = −236 ± 4 JK−1 mol−1. From the temperature dependence of the outer sphere association complex equilibrium constants, the thermodynamic parameters
calculated are ΔH1° = 34.25 ± 1.9 kJ mol−1, ΔS1° = 146 ± 6 J K−1 mol−1 and ΔH2° = 9.4 ± 1.1 kJ mol−1, ΔS2° = 71 ± 3 JK−1 mol−1, which gives a negative ΔG° at all temperatures studied, supporting the spontaneous formation of an outer sphere association
complex. 相似文献
10.
I. Zięborak-Tomaszkiewicz 《Journal of Thermal Analysis and Calorimetry》2006,83(3):611-615
The energies of combustion
in fluorine of gallium nitride and indium nitride in wurzite crystalline structure
have been measured in a two-compartment calorimetric bomb, and new standard
molar enthalpies of formation have been calculated: ΔfHm0(GaN(cr)
298.15 K)= –(163.7±4.2) kJ mol–1
and ΔfHm0(InN(cr) 298.15 K)= –(146.5±4.6) kJ mol–1
. Comparison with the recommended values of the ΔfHm0 nitrides
from the literature is also presented. 相似文献
11.
The basic kinetic parameters of thermal polymerization of hexafluoropropylene, namely, general rate constants, degree of polymerization,
and their temperature and pressure dependences in the range of 230–290 °C and 2–12 kbar (200–1200 MPa) were determined. The
activation energy (E
act = 132±4 kJ mol−1) and activation volume (ΔV
0
≠ = −27±1 cm3 mol−1) were calculated. The activation energy of thermal initiation of polymerization was estimated. The reaction scheme based
on the assumption about a biradical mechanism of polymerization initiation was proposed. 相似文献
12.
S. P. Chen X. X. Meng Q. Shuai B. J. Jiao S. L. Gao Q. Z. Shi 《Journal of Thermal Analysis and Calorimetry》2006,86(3):767-774
A
solid complex Eu(C5H8NS2)3(C12H8N2) has been obtained from reaction of
hydrous europium chloride with ammonium pyrrolidinedithiocarbamate (APDC)
and 1,10-phenanthroline (o-phen⋅H2O)
in absolute ethanol. IR spectrum of the complex indicated that Eu3+
in the complex coordinated with sulfur atoms from the APDC and nitrogen atoms
from the o-phen. TG-DTG investigation provided
the evidence that the title complex was decomposed into EuS.
The
enthalpy change of the reaction of formation of the complex in ethanol, Δr
H
m
θ(l), as –22.214±0.081 kJ mol–1,
and the molar heat capacity of the complex, c
m,
as 61.676±0.651 J mol–1 K–1,
at 298.15 K were determined by an RD-496 III type microcalorimeter. The enthalpy
change of the reaction of formation of the complex in solid, Δr
H
m
θ(s), was calculated as 54.527±0.314 kJ mol–1
through a thermochemistry cycle. Based on the thermodynamics and kinetics
on the reaction of formation of the complex in ethanol at different temperatures,
fundamental parameters, including the activation enthalpy (ΔH
≠
θ),
the activation entropy (ΔS
≠
θ),
the activation free energy (ΔG
≠
θ),
the apparent reaction rate constant (k),
the apparent activation energy (E), the
pre-exponential constant (A) and the reaction
order (n), were obtained. The constant-volume
combustion energy of the complex, Δc
U,
was determined as –16937.88±9.79 kJ mol–1
by an RBC-II type rotating-bomb calorimeter at 298.15 K. Its standard enthalpy
of combustion, Δc
H
m
θ,
and standard enthalpy of formation, Δf
H
m
θ,
were calculated to be –16953.37±9.79 and –1708.23±10.69
kJ mol–1, respectively. 相似文献
13.
The thermodynamics of the conversion of aqueous glucose to fructose has been investigated using both heat conduction microcalorimetry and high pressure liquid chromatography (HPLC). The reaction was carried out in both aqueous TRIS/HCl buffer and in aqueous phosphate buffer in the pH range 7 to 8 using the enzyme glucose isomerase and the cofactors CoCl2 and MgSO4. The temperature range over which this reaction was investigated was 298.15 to 358.15 K (25–85°C). We have found that the enthalpy of reaction is independent of pH over the range 7 to 8. A combined analysis of both the HPLC and microcalorimetric data leads to the following results at 25°C: ΔGo=349±53 J-mol?1, ΔHo=2780±200 J-mol?1, and ΔC p o =76±30 J-mol?1-K?1. The stated uncertainties are based upon an analysis of both the random and systematic errors inherent in the measurements. The temperature dependence of the equilibrium constant K for the process is expressed as $$RinK = - \frac{{349}}{{298.15}} + 2780(\frac{1}{{298.15}} - \frac{1}{T}) + 76(\frac{{298.15}}{T} - 1 + \ln \frac{T}{{298.15}})$$ Comparisons are made with literature data. 相似文献
14.
G. D'Andrea V. Mucciante F. Fantauzzi 《Journal of Thermal Analysis and Calorimetry》2001,65(3):737-743
At 298.15 K, the solubilization of hen ovotransferrin at buffered pH 7.8 (0.08 M Tris⋅HCl buffer, containing 0.1 M CaCl2) and the solubilization of α-chymotrypsin (from bovine pancreas) at non-buffered pH 3.0 (0.001 M HCl) both resulted in large
exothermic reactions, being the apparent ΔHs –2485 in the first case and –780.1 kJ mol–1 in the second case, respectively. By contrast, the complete hydrolysis of ovotransferrin (pH 7.8) achieved by using a-chymotrypsin
(pH 3.0) gave an endothermic reaction with ΔH=+31.84 kJ mol–1.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
15.
Z. H. Zhang Z. C. Tan Y. S. Li L. X. Sun 《Journal of Thermal Analysis and Calorimetry》2006,85(3):551-557
The molar heat capacities of the room temperature
ionic liquid 1-butyl-3-methylimidazolium tetrafluoroborate (BMIBF4)
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)=
195.55+47.230 X–3.1533 X
2+4.0733 X
3+3.9126 X
4 [X=(T–125.5)/45.5] for the solid phase (80~171
K), and C
P,m (J
K–1 mol–1)=
378.62+43.929 X+16.456 X
2–4.6684 X
3–5.5876 X
4 [X=(T–285.5)/104.5] for the liquid phase (181~390
K), respectively. According to the polynomial equations and thermodynamic
relationship, the values of thermodynamic function of the BMIBF4
relative to 298.15 K were calculated in temperature range from 80 to 390 K
with an interval of 5 K. The glass translation of BMIBF4
was observed at 176.24 K. Using oxygen-bomb combustion calorimeter, the molar
enthalpy of combustion of BMIBF4 was determined to
be Δc
H
m
o=
– 5335±17 kJ mol–1. The standard
molar enthalpy of formation of BMIBF4 was evaluated
to be Δf
H
m
o=
–1221.8±4.0 kJ mol–1 at T=298.150±0.001 K. 相似文献
16.
M. A. V. Ribeiro da Silva C. P. F. Santos M. J. S. Monte C. A. D. Sousa 《Journal of Thermal Analysis and Calorimetry》2006,83(3):533-539
The
standard (p0=0.1
MPa) molar enthalpies of formation, ΔfHm0, for
crystalline phthalimides: phthalimide, N-ethylphthalimide
and N-propylphthalimide were derived from
the standard molar enthalpies of combustion, in oxygen, at the temperature
298.15 K, measured by static bomb-combustion calorimetry, as, respectively,
– (318.0±1.7), – (350.1±2.7) and – (377.3±2.2)
kJ mol–1. The standard molar enthalpies of
sublimation, ΔcrgHm0, at T=298.15
K were derived by the Clausius-Clapeyron equation, from the temperature dependence
of the vapour pressures for phthalimide, as (106.9±1.2) kJ mol–1
and from high temperature Calvet microcalorimetry for phthalimide, N-ethylphthalimide and N-propylphthalimide
as, respectively, (106.3±1.3), (91.0±1.2) and (98.2±1.4)
kJ mol–1.
The derived standard molar enthalpies of formation,
in the gaseous state, are analysed in terms of enthalpic increments and interpreted
in terms of molecular structure. 相似文献
17.
Digo Hermínio P. Pinto Susana S. Moura Ramos Joaquim J. 《Journal of Thermal Analysis and Calorimetry》2004,77(3):893-904
The thermal behaviour of salicylsalicylic acid (CAS number 552-94-3) was studied by differential scanning calorimetry (DSC).
The endothermic melting peak and the fingerprint of the glass transition were characterised at a heating rate of 10°C min-1. The melting peak showed an onset at T
on = 144°C (417 K) and a maximum intensity at T
max = 152°C (425 K), while the onset of the glass transition signal was at T
on = 6°C. The melting enthalpy was found to be ΔmH = 28.9±0.3 kJ mol-1, and the heat capacity jump at the glass transition was ΔC
P = 108.1±0.1 J K-1mol-1. The study of the influence of the heating rate on the temperature location of the glass transition signal by DSC, allowed
the determination of the activation energy at the glass transition temperature (245 kJ mol-1), and the calculation of the fragility index of salicyl salicylate (m = 45). Finally, the standard molar enthalpy of formation of crystalline monoclinic salicylsalicylic acid at T = 298.15 K, was determined as ΔfHm
o(C14H10O5, cr) = - (837.6±3.3) kJ mol-1, by combustion calorimetry.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
18.
Joanna Wiśniewska 《Transition Metal Chemistry》2007,32(1):107-111
The kinetics of the oxidation of promazine by trisoxalatocobaltate(III) were studied in the presence of a large excess of
the cobalt(III) in tris buffer solution using u.v.–vis spectroscopy ([CoIII] = (0.6 − 2) × 10−3
M, [ptz] = 6 × 10−5
M, pH = 6.6–7.8, I = 0.1 M (NaCl), T = 288−308 K, l = 1 cm). The reaction proceeds via two consecutive reversible steps. In the first step, the reaction leads to formation of cobalt(II) species and a stable cationic
radical. In the second step, cobalt(III) is reduced to cobalt(II) ion and a promazine radical is oxidized to the promazine
5-oxide. Linear dependences of the pseudo-first-order rate constants (k
1 and k
2) on [CoIII] with a non-zero intercept were established for both redox processes. Rates of reactions decreased with increasing concentration
of the H+ ion indicating that the promazine and its radical exist in equilibrium with their deprotonated forms, which are reactive
reducing species. The activation parameters for reactions studied were as follows: ΔH≠ = 44 ± 1 kJ mol−1, ΔS≠ = −100 ± 4 JK−1 mol−1 for the first step and ΔH≠ = 25 ± 1 kJ mol−1, ΔS≠ = −169 ± 4 J K−1 mol−1 for the second step, respectively. Mechanistic consequences of all the results are discussed. 相似文献
19.
M. A. V. Ribeiro da Silva Cláudia P. F. Santos 《Journal of Thermal Analysis and Calorimetry》2007,87(1):21-25
The standard (p
0=0.1
MPa) molar enthalpy of formation, Δf
H
0
m, for crystalline N-phenylphthalimide
was derived from its standard molar enthalpy of combustion, in oxygen, at
the temperature 298.15 K, measured by static bomb-combustion calorimetry,
as –206.0±3.4 kJ mol–1. The
standard molar enthalpy of sublimation, Δg
cr
H
0
m
, at T=298.15 K, was derived, from high
temperature Calvet microcalorimetry, as 121.3±1.0 kJ mol–1.
The derived standard molar enthalpy of formation, in the gaseous state,
is analysed in terms of enthalpic increments and interpreted in terms of molecular
structure. 相似文献
20.
Jonathan F. Ojo Jide Ige Grace O. Ogunlusi Olanrewaju Owoyomi Esan S. Olaseni 《Transition Metal Chemistry》2006,31(6):782-785
The kinetics of the reactions between Fe(phen)
3
2+
[phen = tris–(1,10) phenanthroline] and
Co(CN)5X3− (X = Cl, Br or I) have been investigated in aqueous acidic solutions at I = 0.1 mol dm−3 (NaCl/HCl). The reactions were carried out at a fixed acid concentration ([H+] = 0.01 mol dm−3) and the second-order rate constants for the reactions at 25 °C were within the range of (0.151–1.117) dm3 mol−1 s−1. Ion-pair constants K
ip for these reactions, taking into consideration the protonation of the cobalt complexes, were 5.19 × 104, 3.00 × 102 and 4.02 × 104 mol−1 dm−3 for X = Cl, Br and I, respectively. Activation parameters measured for these systems were as follows: ΔH* (kJ K−1 mol−1) = 94.3 ± 0.6, 97.3 ± 1.0 and 109.1 ± 0.4; ΔS* (J K−1) = 69.1 ± 1.9, 74.9 ± 3.2 and 112.3 ± 1.3; ΔG* (kJ) = 73.7 ± 0.6, 75.0 ± 1.0 and 75.7 ± 0.4; E
a
(kJ) = 96.9 ± 0.3, 99.8 ± 0.4, and 122.9 ± 0.3; A (dm3 mol−1 s−1) = (7.079 ± 0.035) × 1016, (1.413 ± 0.011) × 1017, and (9.772 ± 0.027) × 1020 for X = Cl, Br, and I respectively. An outer – sphere mechanism is proposed for all the reactions. 相似文献