Enthalpies Of Solution Research Articles

Enthalpy of Solution and Solubility of Carbon Dioxide in Acetone: Experimental Measurements and Modeling

Enthalpy of Solution and Solubility of Carbon Dioxide in Acetone: Experimental Measurements and Modeling

Enthalpy and heat capacity of hydration of the cytostatic Dioxadet

Thermochemical data on hydration of the well-established anticancer agent Dioxadet were obtained. Its enthalpies of solution and sublimation at various temperatures were determined calorimetrically, and on their basis the standard enthalpy (ΔhydrH0 = −154.6 ± 3.6 kJ mol−1) and the standard heat capacity (ΔhydrCp0 = 384 ± 80 J mol−1 K−1) of the transfer of the solute from the state of an ideal gas to an aqueous solution at infinite dilution at 298.15 K were calculated.

Enthalpy of Solution of Rhodium in Iron Studied by 57Fe Mössbauer Spectroscopy

Enthalpy of Solution of Rhodium in Iron Studied by ⁵⁷Fe Mössbauer Spectroscopy

The determination of the solubility, enthalpy, and entropy of solutions of methyl Furan-2,5-Dimethylenedicarbamate and its hydrides in different solvents

The solubilities of methyl furan-2,5-dimethylenedicarbamate (FDC) and methyl tetrahydrofuran-2,5-dimethylenedicarbamate (THFDC) in dimethyl carbonate (DMC), anhydrous ethanol (EtOH) and benzene were studied using the static equilibrium method combined with high-performance liquid chromatography under atmospheric pressure at temperatures ranging from 278.15 K to 318.15 K. The experimental results demonstrate that the solubility of FDC and THFDC exhibits an upward trend as temperature increases. Among the six correlation models used, all of them (modified Apelblat equation, Buchowski-ksiazczak (λh) model, simplified two-parameter equation, polynomial equation, NRTL model and Wilson model) can effectively correlate the solubility data. Notably, the Wilson model demonstrates superior correlation performance compared to others in FDC system and the NRTL model demonstrates superior correlation performance compared to others in THFDC system. Using the modified Van’t Hoff equation and Gibbs equation, we calculated the apparent standard dissolution enthalpy (ΔHsol), the standard dissolution entropy change (ΔSsol), and the standard dissolution Gibbs energy (ΔGsol) for FDC and THFDC in different solvents. The research resulted indicate that all these dissolution processes are non-spontaneous, entropy-increasing endothermic processes. This study provides valuable reference data for crystallization and purification in industrial production.

Solubility of Hydrogen in a WMoTaNbV High-Entropy Alloy.

The WMoTaNbV alloy has shown promise for applications as a solid state hydrogen storage material. It absorbs significant quantities of H directly from the atmosphere, trapping it with high energy. In this work, the dynamics of the absorption of hydrogen isotopes are studied by determining the activation energy for the solubility and the solution enthalpy of H in the WMoTaNbV alloy. The activation energy was studied by heating samples in a H atmosphere at temperatures ranging from 20 °C to 400 °C and comparing the amounts of absorbed H. The solution activation energy EA of H was determined to be EA=0.22±0.02 eV (21.2 ± 1.9 kJ/mol). The performed density functional theory calculations revealed that the neighbouring host atoms strongly influenced the solution enthalpy, leading to a range of theoretical values from -0.40 eV to 0.29 eV (-38.6 kJ/mol to 28.0 kJ/mol).

The structure of CaO–MgO–Al2O3–SiO2 melts and glasses doped with FeOX–NiO

AbstractNeutron and x‐ray diffraction measurements have been performed on CaO–MgO–Al2O3–SiO2 (CMAS) glasses doped with NiO–FeXO at room temperature, along with x‐ray measurements on aerodynamically levitated liquids at ≥2000 K. The disordered structures have been modeled using empirical potential structure refinement to investigate the relation between the aluminosilicate network and the modifying cations. The SiO4 and AlO4 tetrahedra are found to have wider Si–O and Al–O bond distance distributions in the glass, and the first Ca–On coordination shell is highly distorted, redistributing different populations of long and short bonds between the liquid and the glass. The addition of Fe and Ni at low aluminosilicate content increases the number of free oxygens not bonded to AlO4 or SiO4. Mg–O and Fe–O are both found to be predominantly fourfold and fivefold in the liquid and glassy states. Despite these low coordination numbers, their bond angle distributions indicate that they are predominantly in nontetrahedral‐type geometries, with ferrous and ferric iron possessing similar coordination environments. The Ca–O and Mg–O average coordination numbers and enthalpies of solution are consistent with their higher reactivity within relatively acidic aluminosilicate melts.

Investigation of interstitial carbon in the disordered bcc FeCr alloys

The solution enthalpy of interstitial carbon in the ferromagnetic bcc Fe-Cr disordered alloys was calculated. It was found that the enthalpy depends on the number of chromium atoms in the octahedron constituting the octahedral pore and their positions, as well as on the magnetic states of the lattice atoms (Fe/Cr) surrounding the interstitial atom. The lowest cell energy corresponds to the configuration in which only chromium atoms are in the first coordination sphere of the carbon atom. The magnetic moments of the carbon and the nearest lattice atoms show dependency from their distances. For the most energetically favorable configurations, the values of the enthalpy of carbon dissolution in Fe-Cr alloy and in α-Fe are close to each other. It is found that these configurations correspond to the states in which the local magnetic moment on the interstitial carbon atom is close to zero. Also the elastic constants of the Fe-Cr-C alloy were calculated, and it is shown that alloying with carbon slightly increases the elastic properties of Fe-Cr alloys.

Thermochemical and structural study of sodium, iron, and niobium phosphate NASICON solid solutions

Solid solutions NaxFe0.5+0.5xNb1.5-0.5x(PO4)3 (0 ≤ x ≤ 1; x = 2) of NASICON structure (sp.gr. R3-c) and NbOPO4 were prepared via solid-state reaction and characterized by electron microprobe analysis, powder X-ray and neutron diffraction, and differential thermal analysis. The decrease of the a- and b-unit cell parameter prevails over the increase in c-parameters, resulting in nonlinear decrease of the unit cell volume with Na content. Enthalpies of drop solution in molten sodium molybdate solvent at 700 °C were measured by high temperature oxide melt solution calorimetry and were used to derive the enthalpies of formation. Strongly negative enthalpies of formation from elements and from constituent oxides indicate high thermodynamic stability. The mixing enthalpies of solid solutions show negative deviation from the ideality. Negative mixing enthalpies and negative mixing volumes indicate short-range ordering of cations in the structure.

Development of an Activity Coefficient Model for the Aqueous Amino Acid Solution

AbstractThe enthalpy and solubility of aqueous amino acid solutions are essential thermodynamic properties for the modeling of heat and mass balance, and these properties can be estimated by considering the activity coefficient in thermodynamic calculations. In this study, the parameters of a non‐random two‐liquid model were identified using heat capacity and solubility data together to calculate the acceptable activity coefficient for an aqueous amino acid system. As a result, a highly accurate activity coefficient model of an aqueous amino acid solution was developed, and inaccurate alternative solutions regressed with heat capacity or solubility only can be avoided.

Phase transition thermodynamics of organic semiconductors: N,N,N’,N’-tetraphenylbenzidine and 4,4′-bis(N-carbazolyl)-1,1′-biphenyl

In this work, we report a comprehensive study of the phase change thermodynamics of two compounds, N,N,N’,N’-tetraphenylbenzidine (TPB) and 4,4′-bis(N-carbazolyl)-1,1′-biphenyl (CBP), used in the production of organic light-emitting diodes and photovoltaics. The vapor pressures and phase transition enthalpies of these compounds have been previously studied at the elevated temperatures which may not be relevant to the conditions during fabrication and use TPB- and CBP-based materials. In this work, a combination of experimental and computational methods was employed to establish the reliable temperature dependences of the sublimation, fusion, and vaporization enthalpies of TPB and CBP in a wide temperature range. The vapor pressures of both compounds over solid and liquid phases were measured using fast scanning calorimetry. The fusion enthalpies at the melting point were determined by DSC. The isobaric heat capacities of the compounds in crystalline and liquid phases, including the supercooled liquids, were measured using scanning calorimetry. For the first time, the heat capacities of the ideal gas TPB and CBP were computed, considering internal rotation effects. The solution enthalpies in benzene at 298.15 K were measured, providing an independent estimate of the fusion enthalpy temperature dependence. Its consistency with the data on the fusion enthalpies was confirmed using Hess’s and Kirchhoff’s laws of Thermochemistry. Using the obtained results, the available literature data were critically evaluated. The obtained thermodynamic parameters may facilitate optimization of vapor deposition conditions and description of the thermodynamic and kinetic stability of the glassy state of TPB and CBP.

Thermodynamic Description of Liquid Crystalline N(p-n-Alkyloxybenzyliden)-p’-Toluidines with Organic Solvents

Solubility polytherms of nematic (smectic-nematic) N(p-n-alkyloxybenzyliden)-p’-toluidenes (n-alkyl = C4H9, C9H19, C10H21) in organic solvents have been studied. Thermal analysis, visual-polythermal and solubility methods were used. The solution enthalpies of these mesogens in 8 solvents (n-hexane, n-heptane, benzene, p-xylene, cyclohexane, methylcyclohexane, ethanol, n-propanol) were determined. To calculate the solubility polytherms, thermodynamic methods based on the Hildebrand solubility parameters were used. The advantage of the proposed calculation method is that it requires a minimum of experimental parameters (fusion enthalpy and melting temperature of pure mesogen) and the data obtained from the structural formula (group contribution increments) of a mesogen to evaluate its solubility polytherms.

Effect of Sn on stacking fault energies in zirconium and its hydrides

Hydrogen embrittlement in Zr-alloy fuel cladding is a primary safety concern for water-based nuclear reactors. Here we investigated the stabilization of planar defects within the forming hydrides by Sn, the primary alloying element of Zircaloy-4 used in the cladding. In order to explain the formation of hydrides and planar defects observed in our experiments, we performed atomic-scale calculations focusing on the solute interactions with generalized stacking faults in hcp α-Zr and fcc zirconium hydrides. Our calculations showed that an increase in Sn concentration leads to a stabilization of stacking faults in both the α-Zr and hydride phases. However, the solution enthalpy of Sn is lower in the α-Zr as compared to the other hydride phases, indicative of two competing processes of Sn depletion/enrichment at the Zr hydride/matrix interface. This is corroborated by experimental findings, where Sn is less soluble in hydrides and is mostly found trapped at interfaces and planar defects, indicative of stacking faults inside the hydride phases. Our systematic investigation enables us to understand the presence and distribution of solutes in the hydride phases, which provides a deeper insight into the microstructural evolution of such alloy's properties during its service lifetime. Published by the American Physical Society 2024

Thermochemistry of solvation versus vaporisation: Why is the enthalpy of solvation extremely additive?

In the present work, the enthalpies of vaporisation and solvation were compared for various homologous series. It was found that the contribution of the methylene fragment into the enthalpy of solvation in n-heptane is a constant value (4.9 ± 0.1 kJ·mol−1). Simultaneously, the contributions of the methylene group into the enthalpy of vaporisation differ considerably from each other. For example, the contributions of the methylene groups for alkyl acetates and n-alkanes are 4.39 ± 0.04 kJ·mol−1 and 4.99 ± 0.02 kJ·mol−1, respectively. To find an explanation for this phenomenon, the dissolution processes of n-alkanes in homologous series of solvents were compared with the contributions of the methylene groups into vaporisation enthalpy. A relationship between the enthalpy of solution and the contribution of the methylene group into the enthalpy of vaporisation at 298.15 K was discovered. This quantitative relationship shows that the contribution of the methylene fragment into the vaporisation enthalpy is connected with the molecular volumes of n-alkane and solvents and the solution enthalpies of the n-alkane in studied homologous series of solvents.

Grain boundary segregation predicted by quantum-accurate segregation spectra but not by classical models

In alloys, solute segregation at grain boundaries is classically attributed to three driving forces: a high solution enthalpy, a high size mismatch, and a high difference in interfacial energy. These effects are generally cast into a single scalar segregation energy and used to predict grain boundary solute enrichment or depletion. This approach neglects the physics of segregation at many competing grain boundary sites, and can also miss electronic effects that are energetically significant to the problem. In this paper, we demonstrate that such driving forces cannot explain, nor thus predict, segregation in some alloys. Using quantum-accurate segregation spectra that have recently become available for some polycrystalline alloys, we predict strong segregation for gold in aluminum, a solvent-solute combination that does not conform to classical driving forces. Our experiments confirm these predictions and reveal gold enrichment at grain boundaries that is two orders of magnitude over the bulk lattice solute concentration.

New Polymorph of β-Cyclodextrin with a Higher Bioavailability

A new polymorph of anhydrous β-cyclodextrin (polymorph III) was obtained and characterized for the first time using powder X-ray diffraction, infrared spectroscopy, and thermal analysis. The solution enthalpy and time of dissolution in water were determined using solution calorimetry for this polymorph and compared with those of the dried commercial form of β-cyclodextrin (polymorph I), its amorphous form, and 2-hydroxypropyl-β-cyclodextrin. The specific heat capacities of polymorphs I and III were determined using differential scanning calorimetry across a wide range of temperatures, providing enthalpy and Gibbs energy values for the polymorphic transition at 298 K. The affinities of polymorph III and 2-hydroxypropyl-β-cyclodextrin for water were characterized by determining their hydration isotherms, which provided values of hydration Gibbs energy. Being energy-rich, the new-found polymorph of β-cyclodextrin has a significantly higher dissolution rate and an increased affinity for water compared with the dried commercial form of β-cyclodextrin. These properties render the new polymorph promising in industrial applications for guest inclusion in aqueous solutions and pastes, and may be a desirable alternative for water-soluble β-cyclodextrin derivatives.

Modeling of dilution enthalpies within implicit-solvent models for electrolytes

This work deals with the calculation of dilution enthalpies for strong aqueous electrolyte solutions when their thermodynamic properties are described within implicit-solvent models. The solution is modeled as a collection of charged hard spheres in a continuum solvent. A new general expression is obtained that accounts for the variation of the solution permittivity, of the size of the ions, and of the specific volume of the solution, with temperature and concentration. This expression is used to compute the enthalpies of LiCl aqueous solutions at temperatures in the range of 25∘C to 100∘C for concentrations up to 6 mol kg−1. The mean spherical approximation (MSA) model with implicit continuum solvent is employed to describe the thermodynamic properties of these solutions.

Synthesis and thermodynamic properties of 4ZnO·B2O3·H2O with three different morphologies

Polycrystalline 4ZnO·B2O3·H2O with flower-like, spherical-like and sheet-like morphologies have been synthesized and characterized by XRD, TG–DSC, SEM and TEM. The molar enthalpies of solution of 4ZnO·B2O3·H2O with different morphologies in 1 mol L−1 HCl(aq) were measured. With the incorporation of the previously determined enthalpy of solution of H3BO3 in 1 mol L−1 HCl(aq), the enthalpy of solution of ZnO in (HCl + H3BO3)(aq) and the standard molar enthalpies of formation of ZnO(s), H3BO3(s) and H2O(l), the standard molar enthalpies of formation of 4ZnO·B2O3·H2O with flower-like, spherical-like, and sheet-like morphologies were calculated to be -(3033.91 ± 2.03), -(3030.91 ± 2.03) and -(3025.94 ± 2.04) kJ·mol−1, respectively.

Thermochemical Study of Bismuth Cobalt Dysprosium Oxide: The Enthalpy of Formation and Lattice Enthalpy

Bismuth cobalt dysprosium oxide of composition Bi12.5Dy1.5CoO22.325 has been prepared by solid-state reactions. The compound has a cubic structure (space group Fmm) with the unit cell parameter a = 0.55279(5) nm. The solution enthalpy and standard enthalpy of formation of Bi12.5Dy1.5CoO22.325 have been measured by solution calorimetry: ΔsolH0 = −1017.0 ± 7.5 kJ/mol, and ΔfH0 = −5338.8 ± 19.9 kJ/mol. The lattice enthalpy has been calculated using the Born–Haber cycle: ΔlatH0 = −99020 kJ/mol. The lattice enthalpy increases in magnitude as the lanthanide radius decreases in the neodymium–dysprosium–holmium series.

Re-evaluation of solution enthalpies of aliphatic hydrocarbons functional derivatives and terpenes in n-heptane and their validation by thermochemical consistency

The aim of this study was to investigate the influence of the position of the functional group and the choice of solvent on the relationships between the enthalpies of solution and the alkyl chain length of aliphatic hydrocarbons functional derivatives. The results show that the selection of an appropriate solvent for functional derivatives, such as methanol for alcohols and acetonitrile for alkyl nitriles, is not a viable option because the enthalpies of solution increase non-linearly with increasing alkyl chain length, leading to significant errors in the prediction of enthalpies of solution.On the other hand, the enthalpies of solution of aliphatic hydrocarbons functional derivatives in n-heptane decrease non-linearly with increasing number of methylene fragments in the chain. In this work, complementary measurements of the enthalpies of solution of homologous series of dialkyl ethers, alkyl-amines and nitroalkanes in n-heptane were carried out. These new data were used to develop an approach to estimate the enthalpies of solution of dialkyl ethers, alkyl-nitriles and alkyl-amines in n-heptane. The absolute deviations between predicted and experimental solution enthalpies for most of the investigated compounds do not exceed 0.5 kJ mol−1. The proposed approach to predict the solution enthalpies of aliphatic hydrocarbon derivatives in n-heptane was applied to estimate the enthalpies of fusion of 11 aliphatic hydrocarbon derivatives, which agreed well with the values obtained by differential scanning calorimetry. Complementary vapour pressure measurements were carried out on cyclic aliphatic hydrocarbons from the terpene family using a transpiration method to derive their enthalpies of vaporisation. The latter were used for independent validation of the re-evaluated solution enthalpies.

THERMODYNAMIC MAGNITUDES OF MIXING AND SOLVATION OF ACETAMINOPHEN IN ETHANOL + WATER COSOLVENT MIXTURES.

Based on van't Hoff and Gibbs equations the thermodynamic functions free energy, enthalpy, and entropy of solution, mixing and solvation of acetaminophen in ethanol + water cosolvent mixtures, were evaluated from solubility data determined at several temperatures. The solubility was greater at 90% m/m of ethanol at all temperatures studied. This result shows clearly the cosolvent effect present in this system. The solvation of this drug in the mixtures increases as the ethanol proportion is also increased. By means of enthalpy-entropy compensation analysis, a more complex behavior for solution was found with respect to that exposed previously in literature. From 0% up to 10% m/m of ethanol and from 90% up to 100% of ethanol, entropy driving was found, while from 20% up to 60% of ethanol, enthalpy driving was found. These facts would be explained in terms of a losing of water-structure in addition to a diminishing in the energy required for cavity formation in the solvent for mixtures from 20% up to 60% of ethanol. Nevertheless in the ethanol-rich mixtures the intermolecular mechanisms involved in the solution process should be more complex including other physicochemical considerations.