共查询到20条相似文献,搜索用时 46 毫秒
1.
G. K. Moiseev 《Russian Journal of Physical Chemistry A, Focus on Chemistry》2007,81(2):308-308
The values of ΔH°298, S°298, H°298–H°0, T, ΔH fus, and C p(T), as well as the temperature dependences of the Gibbs energy function, are calculated for Bi8O11 oxide by proven computational methods. 相似文献
2.
G. G. Gorboletova A. A. Metlin 《Russian Journal of Physical Chemistry A, Focus on Chemistry》2016,90(9):1774-1777
The Cu2+–glycine–L-histidine system is studied calorimetrically at 298.15 K and an ionic strength of 0.2, 0.5, and 1.0 in aqueous solutions containing potassium nitrate. The standard thermodynamic parameters (ΔrH°, ΔrG°, ΔrS°) of complexation processes are determined. 相似文献
3.
De Stefano C Gianguzza A Piazzese D Sammartano S 《Analytical and bioanalytical chemistry》2005,383(4):587-596
Acid–base behaviour of a commercial sodium alginate extracted from brown seaweed (Macrocystis pyrifera) has been investigated at different ionic strengths (0.1≤I/mol l?1≤1.0) and in different supporting electrolytes (Et4NI, NaCl, KCl, LiCl, NaCl+MgCl2), with the aim of examining the influence of ionic medium on the proton-binding capacity and of quantifying the strength of interaction with light metal ions in the perspective of speciation studies in natural aqueous systems. Potentiometric ([H+]-glass electrode) and titration calorimetric data were expressed as a function of the dissociation degree (α) using different models (Henderson–Hasselbalch modified, Högfeldt three parameters and linear equations). The dependence on ionic strength of the protonation constants was taken into account by a modified specific interaction theory model. Differences among different media were explained in terms of the interaction between polyanion and metal cations of the supporting electrolytes. Quantitative information on the proton-binding capacity, together with the stabilities of different species formed, is reported. Protonation thermodynamic parameters, at α=0.5, are log K H=3.686±0.005, ΔG 0=?21.04±0.03 kJ mol?1, ΔH 0=4.8±0.2 kJ mol?1 and TΔS 0=35.7±0.3 kJ mol?1, at infinite dilution. Protonation enthalpies indicate that the main contribution to proton binding arises from the entropy term. A strict correlation between ΔG and TΔS was found, TΔS=?9.5–1.73 ΔG. Results are reported in light of building up a chemical complexation model of general validity to explain the binding ability of naturally occurring polycarboxylate polymers and biopolymers. Speciation profiles of alginate in the presence of sodium and magnesium ions, naturally occurring cations in natural waters, are also reported. 相似文献
4.
A. I. Lytkin N. V. Chernyavskaya A. S. Chernov V. E. Litvinenko 《Russian Journal of Inorganic Chemistry》2016,61(4):526-530
The thermodynamic characteristics of complexation between ethylenediamine-N,N'-disuccinic acid (H4Y; EDDA) and Ho3+ ion were determined calorimetrically and potentiometrically at 298.15 K and ionic strengths of 0.1, 0.5, 1.0, and 1.5 (KNO3). The logK, ΔrG, ΔrH, and ΔrS values for the formation of HoY– and HOHY complexes were calculated at the studied and zero ionic strength values. The changes in thermodynamic parameters of the reactions are discussed. 相似文献
5.
A method has been purposed to calculate some of the thermodynamic quantities for the thermal deformation of a smectite without using any basic thermodynamic data. The Hanç?l? (Keskin, Ankara, Turkey) bentonite containing a smectite of 88% by volume was taken as material. Thermogravimetric (TG) and differential thermal analysis (DTA) curves of the sample were obtained. Bentonite samples were heated at various temperatures between 25–900°C for the sufficient time (2 h) until to establish the thermal deformation equilibrium.Cation-exchange capacity (CEC) of heated samples was determined by using the methylene blue standard method. The CEC was used as a variable of the equilibrium. An arbitrary equilibrium constant (K a) was defined similar to chemical equilibrium constant and calculated for each temperature by using the corresponding CEC-value. The arbitrary changes in Gibbs energy (ΔG a 0 ) were calculated from K a-values. The real change in enthalpy (ΔH 0) and entropy (ΔS 0) was calculated from the slopes of the lnK vs. 1/T and ΔG vs. T plots, respectively. The real changes in Gibbs energy (ΔG 0) and real equilibrium constant (K) were calculated by using the ΔH 0 and ΔS 0 values. The results at the two different temperature intervals are summarized as below: ΔG 1 0 =ΔH 1 0 ?ΔS 1 0 T=?RTlnK 1=47000?53t, (200–450°C), and ΔG 2 0 =ΔH 2 0 -ΔS 2 0 T=?RTlnK 2=132000?164T, (500–800°C). 相似文献
6.
Thermodynamic characteristics of stepwise dissociation of glycyl-glycyl-glycine in aqueous solutions
A. I. Lytkin V. V. Chernikov O. N. Krutova G. G. Gorboletova I. A. Skvortsov A. S. Korchagina 《Russian Journal of Inorganic Chemistry》2017,62(2):240-243
The heats of interaction between glycyl-glycyl-glycine and solutions of nitric acid and potassium hydroxide are determined by calorimetry at 298.15 K and ionic strengths of 0.25, 0.50, and 0.75 in the presence of KNO3. The standard thermodynamic characteristics (Δr H°, Δr G°, and Δr S°) of acid–base interaction in aqueous solutions of the peptide are calculated. The effect of background electrolyte concentration on the enthalpy of dissociation of glycyl-glycyl-glycine is discussed. 相似文献
7.
Min Shu Liang Zhu Min Yuan Liyu Wang Yanfei Wang Libin Yang Zuoliang Sha Meng Zeng 《Journal of solution chemistry》2017,46(11):1995-2013
The solubility of 4-(4-hydroxyphenyl)-2-butanone (raspberry ketone) in six pure solvents was experimentally determined at temperatures ranging from 283.15 to 313.15 K under the pressure 0.10 MPa by employing a gravimetrical method. The experimental results indicate that the solubility of raspberry ketone in all studied solvents is temperature dependent, a rise in temperature brings about an increase in solubility. The experimental solubility data of raspberry ketone in six pure solvents (acetone, ethanol, ethyl acetate, n-propyl alcohol, n-butyl alcohol, and distilled water) was correlated by using several commonly used thermodynamic models, including the Apelblat, van’t Hoff and λh equations. The results of the error analysis indicate that the van’t Hoff equation was able to give more accurate and reliable predictions of solubility with root-mean-square deviation less than 0.56%. Furthermore, the changes of dissolution enthalpies (Δdiss H°), dissolution entropies (Δdiss S°) and dissolution Gibbs energies (Δdiss G°) of raspberry ketone in the solvents studied were estimated by the van’t Hoff equation. The positive value of Δdiss H°, Δdiss S°, and Δdiss G° indicated that these dissolution processes of raspberry ketone in the solvents studied were all endothermic and enthalpy-driven. 相似文献
8.
R. Kh. Mudarisova L. A. Badykova 《Russian Journal of Physical Chemistry A, Focus on Chemistry》2016,90(3):592-595
The thermodynamics of complexation of arabinogalactan with salicylic and p-aminobenzoic acids in aqueous solutions is studied by means spectroscopy. The standard thermodynamic characteristics (ΔH°; ΔG°; ΔS°) of complexation are calculated. 相似文献
9.
L. Pham Thi T. R. Usacheva T. M. Khrenova V. A. Sharnin 《Russian Journal of Physical Chemistry A, Focus on Chemistry》2017,91(7):1235-1240
Thermodynamic functions Δr H, Δr G, and TΔr S of the complex formation between Cu2+ and triglycine in water–ethanol solutions are calculated on the basis of calorimetric data. It is found that raising the concentration of EtOH results in a monotonic increase in the exothermic effect of [CuHL]2+ complex formation due to the weakening of triglycine solvation with the mutual compensation of ion solvation contributions. The enthalpy of [CuL]+ complex formation has an exothermic maximum at 0.1?0.3 molar fractions of EtOH due to competition between the solvation contributions from ions and ligands. 相似文献
10.
Jianbing Hua Chao Wu Liming Zou Shuyun Chen Hongwei Lu Yongjing Xu Xianyang Peng 《Journal of Thermal Analysis and Calorimetry》2017,128(3):1273-1278
In this study, a series of binary mixtures of N-butyl stearate (nBS) and methyl palmitate (MP) were used to produce a novel composite phase change material (CPCM) for potential application in the eastern China, and their thermal properties were investigated by differential scanning calorimetry (DSC). The results of DSC indicated that the mixture consisting of 10 mass% nBS and 90 mass% MP is optimum as the CPCM in terms of the phase change temperature ranges (T f = 19.74–5.59 °C; T m = 18.34–33.80 °C) and latent heats (ΔH f = 176.8 J g?1; ΔH m = 189.3 J g?1). On the other hand, the thermal reliability and chemical stability of the CPCM after 120, 180, 240, 300, 360 and 500 accelerated thermal cycling tests were studied by DSC and fourier transform infrared (FTIR) analysis. The results demonstrated that the CPCM had good thermal reliability and chemical stability. 相似文献
11.
Song-tao Xiao Guo-an Ye Li Li Xie-chun Liu He Yang Hui-bo Li Zhong-wei Yuan 《Journal of Radioanalytical and Nuclear Chemistry》2017,311(3):1565-1575
The 3D structure of hydrazine derivatives was optimized and their energy was calculated by density functional theory with B3LYP method and 6-311 + (3d, 3p) basis set. The results show that the reaction relationship between the structure of hydrazine derivatives and Np(VI) could be explained by two quantitative structure–activity relationships equations. In Eq. 1, the lowest unoccupied molecular orbital energy is a major factor affecting the reduction rate, and it is negatively correlated with the reaction rate. In Eq. 2, the molecular dipole moment and hydrophobic parameters are the most important factors affecting the reduction rate. The molecular dipole moment is negatively correlated with the reaction rate, but the hydrophobic parameter is positively correlated with the reaction rate. 相似文献
12.
S. N. Gridchin 《Russian Journal of Physical Chemistry A, Focus on Chemistry》2016,90(12):2499-2501
The formation of complexes of nickel(II) with L-homoserine at 298.15 K and ionic strengths I = 0.5, 1.0, and 1.5 (KNO3) are investigated by potentiometry and calorimetry. Standard characteristics of studied equilibria (log K°, ΔrG°, ΔrH°, and ΔrS°) are determined. 相似文献
13.
L. A. Kochergina A. V. Emel’yanov O. N. Krutova G. G. Gorboletova 《Russian Journal of Physical Chemistry A, Focus on Chemistry》2007,81(10):1632-1638
The heats of interaction of L-phenylalanine with solutions of nitric acid and potassium and lithium hydroxides were determined calorimetrically at 288.15, 298.15, and 308.15 K and solution ionic strengths of 0.5, 0.75, and 1.0 in the presence of LiNO3 and KNO3. The standard thermodynamic characteristics (Δr H°, Δr G°, Δr S°, and ΔC p ° of acid-base interactions in aqueous solutions of L-phenylalanine were calculated. The influence of the concentration of background electrolytes and temperature on the heats of dissociation of L-phenylalanine was considered. A comparative analysis of the standard thermodynamic characteristics of step dissociation of L-phenylalanine and alanine was performed in terms of the modern concepts of the structure and physicochemical properties of these compounds and their solutions. 相似文献
14.
A quantum-chemical study of the thermodynamic properties of the CNOH<Subscript>3</Subscript> isomers
V. V. Turovtsev I. V. Stepnikov A. N. Kizin Yu. D. Orlov 《Russian Journal of Physical Chemistry A, Focus on Chemistry》2007,81(2):317-319
The B3LYP/6-311++G(3df,3pd) DFT method was used to determine the geometry and vibrational frequencies for the formamide, formaldoxime, nitrosomethane, oxaziridine, and formimide. The potential energy functions of the hindered internal rotations were calculated. The conformers of formaldoxime and formimide were determined. For all the molecules, including the conformers, the thermodynamic characteristics Δf H° (298 K), S°(298 K), C p(298 K), and Δf G° (298 K) were determined. The temperature dependences C p(T) within 298–1500 K were represented in the form of cubic polynomials. 相似文献
15.
Faisal I. Chowdhury M. U. Khandaker H. Zabed M. R. Karim H. A. Kassim A. K. Arof 《Journal of solution chemistry》2017,46(5):1104-1120
Thermodynamic activation parameters, enthalpies (ΔH ?), entropies (ΔS ?) and Gibbs energies (ΔG ?) for viscous flow of the systems tert-butanol (TB)+n-butylamine (NBA), TB+di-n-butylamine (DBA) and TB+tri-n-butylamine (TBA) have been calculated from measured density and viscosity data at temperatures ranging from 303.l5 to 323.15 K over the composition range 0 ≤ x 2 ≤ 1, where x 2 is the mole fraction of TB. For all systems, the corresponding excess properties ΔH ?E, ΔS ?E and ΔG ?E have been determined, which are negative in the whole range of composition. The observed negative excess activation properties have been accounted for in terms of dispersive forces and H-bonding. The derived properties are well represented by fourth degree polynomial equations whereas the excess properties could be fitted to third degree Redlich–Kister polynomial equations. Furthermore, the viscosities have been predicted by using the UNIFAC–VISCO model, Grunberg–Nissan model and McAllister three-body interaction model. The UNIFAC–VISCO model and Grunberg–Nissan model do not show good agreement with the experimental data, whereas the McAllister three-body interaction model shows excellent agreement for all three systems, with small average absolute percent deviations (AAD% = 0.6–2.3). The DFT-B3LYP method with the 6-311 G (d, p) basis set has been employed for the optimization of the geometry and calculation of the total energies of the pure compounds and their binary complexes. 相似文献
16.
Mansour Mohamed Mohamed N. Abd-el Salam M. A. Abdel-Rahim A. Y. Abdel-Latief E. R. Shaaban 《Journal of Thermal Analysis and Calorimetry》2018,132(1):91-101
Chalcogenide glasses of (As50Se50)100?xAgx (0 ≤ x ≤ 25) were prepared using the melt quenching technique under non-isothermal conditions. Differential scanning calorimetry curves measured at different heating rates (5 ≤ β ≤ 40 K min?1) are used to characterize the as-quenched samples. The thermal stability was monitored through the calculation of the temperature difference T c ? T g, stability parameter S and crystallization rate factor K p. The glass-forming ability (GFA) was investigated on the basis of Hurby parameter H r which is a strong indicator of GFA. In addition, the activation energy of glass transition E t, activation energy of crystallization E c and Avrami exponent n of the studied compositions were determined. The mechanism of crystallization was found to be a combination of two- and three-dimensional crystal growth. 相似文献
17.
In Vitro Binding of Furadan to Bovine Serum Albumin 总被引:1,自引:0,他引:1
Under physiological conditions, the interaction between furadan (FRD) and bovine serum albumin (BSA) was investigated by spectroscopy including fluorescence emission, UV-visible absorption, scattering, circular dichroism (CD) spectra, synchronous and three-dimensional fluorescence spectra. The observed binding constant K b and the number of binding sites n were determined by the fluorescence quenching method. The distance r between donor (BSA) and acceptor (FRD) was obtained according to the Förster theory of non-radiation energy transfer. The enthalpy change (ΔH θ ), Gibbs energy change (ΔG θ ) and entropy change (ΔS θ ) at four different temperatures were calculated. The process of binding was proposed to be a spontaneous process since the ΔG θ values were negative. The positive ΔS θ and ΔH θ values indicated that the interaction of FRD and BSA was driven mainly by hydrophobic interactions. The addition of FRD to BSA solutions leads to enhancement in scattering intensity, exhibiting the formation of an aggregate in solution. CD spectra, synchronous and three-dimensional fluorescence spectra were used to measure the structural change of BSA molecules with FRD present. 相似文献
18.
Sai-Bo Yu Ju-Lan Zeng Sai-Ling Sun Lei Zhou Yu-Hang Chen Liu-Bin Song Zhong Cao Li-Xian Sun 《Journal of Thermal Analysis and Calorimetry》2017,129(1):189-199
Solar absorption cooling is a wonderful method to provide cold energy by exploiting solar energy. Phase change materials (PCMs) that store latent thermal energy are indispensible in solar absorption cooling system. It is worthwhile to find new PCMs due to the demanding on the temperature of the stored thermal energy which in turn would power the absorption chiller. In this paper, two compounds: 1-bromo-2-methoxynaphthalene (compound 1) and 2,2′-diphenyl-4,4′-bi(1,3-dioxane)-5,5′-diol (compound 2), were selected as potential PCMs. Their thermal energy storage properties and thermal stability were characterized by differential scanning calorimetry and thermogravimetric analysis. The results showed that both compounds could be applied as good PCMs in solar absorption cooling systems. Compound 1 melted at 356.82 K with the ΔH of 98.81 J g?1, while compound 2 melted in a broad temperature range with the melting point of 466.26 K and the ΔH of 101.4 J g?1. Both compounds exhibited good thermal stability. Furthermore, the molar specific heat capacities of these two compounds were measured by temperature-modulated differential scanning calorimetry from 198.15 K to the temperature that they started to decompose, and the thermodynamic functions of [H T–H 298.15] and [S T–S 298.15] were calculated based on the specific heat capacities data. 相似文献
19.
N. N. Smirnova T. G. Kulagina T. A. Bykova V. N. Kizhnyaev T. L. Petrova 《Russian Journal of Physical Chemistry A, Focus on Chemistry》2009,83(1):13-19
The temperature dependences of the heat capacities of 5-vinyltetrazole and poly-5-vinyltetrazole were measured by adiabatic vacuum calorimetry over the temperature range 6-(350–370) K with errors of ~0.2%. The results were used to calculate the thermodynamic functions of the compounds, C p ° , H °(T) - H °(0), S °(T), and G °(T) - H °(0), over the temperature range from T → 0 to 350–370 K. The energy of combustion of 5-vinyltetrazole and poly-5-vinyltetrazole was measured in an isothermic-shell static bomb calorimeter. The standard enthalpies of combustion Δ c H ° and thermodynamic characteristics of formation Δf H °, Δf S °, and Δf G ° at 298.15 K and p = 0.1 MPa were calculated. The results were used to determine the thermodynamic characteristics of polymerization of 5-vinyltetrazole over the temperature range from T → 0 to 350 K. 相似文献
20.
Mohammad S. Al Tuwaim Adel S. Al-Jimaz Khaled H. A. E. Alkhaldi 《Journal of solution chemistry》2018,47(3):449-467
Viscosities, η, and surface tensions, σ, of binary systems of phenetole (ethoxy benzene or ethyl phenyl ether) with N-methyl-2-pyrrolidone, N,N-dimethylformamide or with tetrahydrofuran were measured over the entire mole fraction range and at (298, 303 and 308) K. The experimental data was used to compute the deviations in viscosity, Δη, and surface tension, Δσ. Values of the excess Gibbs energy of activation G*E, surface entropy S σ and surface enthalpy H σ were calculated. Viscosity data of the binary systems were calculated using the Grunberg and Nissan and the three-body and four-body McAllister correlations. The Redlich–Kister method was used for evaluation of coefficients and standard deviations for Δη, Δσ and G*E. The results were interpreted in terms of the probable effect of molecular interactions between components as well as polarity. 相似文献