Excess Molar Free Energies Research Articles

Excess properties, computational chemistry and spectroscopic analyses of 1,2-propanediamine + n-propanol/isopropanol binary mixtures

To understand excess properties and intermolecular interactions of 1,2-propanediamine and n-propanol/isopropanol binary mixtures, their density and viscosity were systemically measured at T = (298.15–318.15) K under atmospheric pressure (1005 hectopascals in Tianjin, China), and their excess molar volume (VmE), viscosity deviation (Δη) and excess viscous activation free energy (ΔG*E) were also calculated. From the results of VmE, it can be inferred that two n-propanol/isopropanol molecules and one 1,2-propanediamine molecule have the strongest binding capacity and form the most stable intermolecular hydrogen bonds. The experimental density and kinematic viscosity were correlated and predicted by several semi-empirical models, among which the Jouyban-Acree model had a better fit for the density and the McAllister four-body equation had a better fit for the kinematic viscosity, and the calculated results of VmE, Δη and ΔG*E were analyzed using the R-K equation. Meanwhile, the apparent molar volume, partial molar volume, thermal expansion coefficient and viscous activation parameters of 1,2-propanediamine and n-propanol/isopropanol solutions were calculated and analyzed. After that, the existence of intermolecular hydrogen bonds (IHBs) between 1,2-propanediamine and n-propanol/isopropanol binary mixtures was demonstrated on the basis of computational chemistry. And then, the IHBs between 1,2-propanediamine and n-propanol/isopropanol binary mixtures with the form of –OH···NH2– were further confirmed based on Raman, ultraviolet (UV), fluorescence (FLS) and nuclear magnetic resonance (1H NMR) spectral technologies.

Development of Higher‐Order Interaction Parameter Formalisms for a Ternary Solution in a Thermodynamically Consistent Manner

Wagner's interaction parameter formalism (WIPF), being thermodynamically inconsistent (on truncation) and limited in applicability to a very dilute solution, is modified, ever so often, to extend its utility. In WIPF, the activity coefficients of the solutes present in a solution are represented by Taylor's series. Herein, the analogy between the activity coefficient expression obtained by two different ways, that is, 1) by partially differentiating the (Redlich–Kister) polynomial representing the excess molar free energy and 2) by expressing the truncated Taylor's series (WIPF) along with the special relationships obtained between the interaction parameters by applying Gibbs–Duhem equation, is exhibited. WIPF truncated after the second order along with the special relations obtained by applying Gibbs–Duhem equation and the unified interaction parameter formalism (UIPF) truncated after the first order are identical to the Darken's quadratic formalism which is thermodynamically consistent and restricted to a limited concentration range. Therefore, these formalisms cannot be universal. Higher‐order terms must be included in Redlich–Kister polynomials or in WIPF in a thermodynamically consistent manner to extend its utility for a wide concentration range. Herein, a general quadratic and higher‐order formalisms such as cubic and quartic are developed for a ternary system.

Densities, Viscosities, and Excess/Deviation Properties of the Ternary System 2-(Methylamino)ethanol + Dimethyl Sulfoxide + Water and the Binary Subsystems

Densities and viscosities of the ternary system 2-(methylamino)ethanol (MAE) + DMSO + water and its corresponding binary constituents have been measured experimentally over the whole composition range and the temperature range from 293 to 353 K. The excess molar volumes (VE), viscosity deviations (Δη), and excess free energies of activation (ΔG*E) of the binary systems were correlated with the Redlich–Kister equation, while the experimental data of ternary mixtures were represented by using Nagata–Tamura, Cibulka, Singh, and Redlich–Kister equations. For binary mixtures, the VE values of aqueous DMSO and aqueous MAE are negative but positive for the nonaqueous blend of MAE + DMSO. The values of Δη and ΔG*E of aqueous binary systems are positive and negative, respectively, for the binary mixture of MAE + DMSO over the whole composition range and at all temperatures. These behaviors can be interpreted with molecular interactions and structural effects. The V123E and Δη123 values have also been derived from the experimental data of the ternary system. It was found that the V123E values are negative except for the regions highly deficient in water. The values of Δη123 become more positive in both H2O- and MAE-rich regions that were highly poor in DMSO. The observed behaviors indicate that the properties of the ternary system investigated are dominated by binary effects.

Density, viscosity and intermolecular interaction of polyethylene glycol 300 + N, N-Dimethylformamide binary mixture

ABSTRACT The density (ρ) and kinematic viscosity (v) data of polyethylene glycol 300 (PEG) + N, N-Dimethylformamide (DMF) binary mixture were determined under atmospheric pressure and six temperatures of T = (293.15–318.15) K. From these experimental results, the thermodynamic parameters like excess molar volume (V m E), apparent molar volume (Vφ, 1 and Vφ, 2) and partial molar volume ( and ), viscosity deviation (Δη) and excess Gibbs activation free energy (ΔG*E) were systemically counted, in which the standard deviation between the experimental and calculated data was estimated by fitting the Redlich-Kister formula. The intermolecular interaction of DMF with PEG was analysed by FTIR and UV-vis spectral technologies.

Phase equilibria and thermodynamic description of solid dispersions of 8-hydroxyquinoline – 4-chlorobenzoic acid drug system

In present article 8-hydroxyquinoline (HQ)-4-chlorobenzoic acid (CBA) binary drug system has been undertaken to study phase diagram and thermodynamic contribution in the system in terms of partial and integral mixing and excess functions. The phase equilibria of the system undertaken shows the formation of 1:1 addition compound C and its eutectic E at 214º and199º c respectively. The negative value of molar free energy of mixing (∆GM) of solid dispersion at 0.810 and 0.895 mole fraction of CBA suggests that the mixing in these cases is spontaneous. The integral molar enthalpy of mixing value corresponds to the value of excess integral molar free energy of the system favors the regularity in the binary solutions. The positive value of excess free energy (gE) for all the eutectic and noneutectic solid dispersion suggests an association of weaker nature between unlike molecules and of stronger nature between like molecules. Gibbs-Duhem equation gives the graphical solution of partial molar heat of mixing (Hi-M), activity and activity coefficient of a particular constituent in the binary mix. Interfacial roughness of the binary solid dispersion has also been explained. Keywords: Binary drug dispersion, phase diagram, activity, activity coefficient, mixing and excess function.

Electromotive force study of lanthanum in liquid bismuth

The thermodynamics of lanthanum (La) dissolved in liquid bismuth (Bi) were determined by means of the electromotive force (EMF) measurement using a galvanic cell consisting of molten chloride and liquid bismuth at the temperature ranging from 723 K to 975 K. A considerable increase of the activity coefficient with temperature was observed for the La-Bi alloy. In addition, the activity coefficient increased slightly with the concentration of La. The values of the molar excess free energy of formation, the excess enthalpy, and the excess entropy of La dissolved in Bi were determined. The heat of formation of liquid La-Bi alloys (ΔHLa–BiM) was deduced from the measured activity coefficient. There is a linear dependence of experimental ΔHLa–BiM on the La concentration.

Measurement of Activity of Indium in Liquid Bi-In-Sn Alloys by EMF Method

The electrochemical technique based on a molten salt electrolyte galvanic cell has been used to measure the activity of indium in liquid Bi-In-Sn alloys in the temperature range of 723 K to 855 K along three ternary sections. The activity of tin in Bi-Sn binary alloys has also been measured by the same technique in the above temperature range. The activity of indium in Bi-In-Sn alloys shows negative deviation from Raoult’s law for most of the compositions and slight positive deviations for a few indium-rich compositions. The ternary excess molar free energies have been calculated by Darken’s treatment. Isoactivity curves at 813 K in the ternary Bi-In-Sn alloys were derived by combining the activity data of In-Sn and Bi-In alloys. The values of excess molar free energy obtained in this study are compared with those calculated from the Muggianu model at 813 K.

Measurement of zinc activity in the ternary In–Zn–Sn alloys by EMF method

Activity of zinc in liquid In–Zn–Sn alloys has been measured by electrochemical technique based on molten salt electrolyte galvanic cell in the temperature range 753–853K along three ternary sections of Znx(InySn1−y)1−x where y=0.67, 0.50 and 0.33. The activity of indium in In–Sn binary alloys has also been measured by the same technique in the same temperature range. The activity of Zinc in In–Zn–Sn alloys shows positive deviation from the Raoult's law over entire range of composition. The activity of indium in In–Sn alloys shows negative deviations from ideality for entire composition. The excess molar free energies have been computed by the Darken's treatment of the ternary solutions using In–Sn binary data and ternary data in this study. Isoactivity curves at 813K in the ternary In–Zn–Sn alloys were derived by combining the activity data of In–Zn and Sn–Zn alloys. The values of excess molar free energy in this study are in good agreement with those calculated from the general model calculation proposed by Chou.

Density and Viscosity of Binary Mixtures of n-Butyl Acetate with Ketones at (298.15, 303.15, 308.15, and 313.15) K

Densities and viscosities of binary mixtures of n-butyl acetate with acetophenone, cyclopentanone, cyclohexanone, and 3-pentanone were determined over the entire composition range at temperatures (298.15 to 313.15) K and at normal atmospheric pressure. From the experimental data, the excess molar volumes VE and excess free energy of activation of viscous flow ΔG*E were calculated. These results were fitted to the Redlich–Kister polynomial equation. The excess molar volumes for all of the studied systems are negative over the whole composition range and at all of the studied temperatures. The experimental mixture viscosity data have been correlated using Grunberg–Nissan, Heric (two-parameter), and McAllister (four-body) models at different temperatures.

<b>Structural interaction of novel dendrimer and subunits with water estimated with excess molar volumes, viscosities and free energies</b>

The 2,4,6-tridiethylmalonatetriazine (TDEMTA) dendrimer and subunits developed interaction potential when mixed with water due to structural reorientation. Thus excess volumes (VE10-6 m3 mol-1), viscosities (ηE/0.1 N s m-2) and molar free activation energy (ΔGE kJ mol-1 K–1) from 0.63 to 10 mm kg-1 of 2,4,6-trichlorotriazine (TCT), 2,4,6-triacetotriazine (TAT), 2,4,6-trihydroxytriazine (THT) and 2,4,6-tridiethyl- malonatetriazine (TDEMTA) have been reported with water at 298.15 K. The VE and ηE positive values inferred deviations from ideal behavior with an adequate potential to cause solute-solvent interactions. The ideally the VE = 0 and ηE = 0, and their ηE0 noted as limiting excess viscosities were as TAT > 2,4,6-trihydroxytriazine (THT) = 2,4,6-trichlorotriazine (TCT) > 2,4,6-tridiethylmalonatetriazine (TDEMTA). The ΔGE > 0, was higher by 15.15 kJ mol-1 K–1 with weaker interacting response of the dendrimer. The 3 x 10-4 mm kg-1 2,4,6-trihydroxytriazine (THT) showed higher ΔGE values with an abrupt decrease with much disruption in molecular interaction similar to surfactant behavior. The lowest ΔGE values were with the 2,4,6-trichlorotriazine (TCT) due to comparatively higher interactions of the chloride ion.KEY WORDS: Excess viscosity, Trichlorotriazine, Hydrophilic, Hydrophobic, HydrodynamicBull. Chem. Soc. Ethiop. 2011, 25(1), 119-126.

Thermodynamic investigations of Sn–Zn–Ga liquid solutions

Activity of zinc in liquid Sn–Zn–Ga alloys has been measured by electrochemical technique based on molten salt electrolyte galvanic cell in the temperature range 723–823 K along three pseudo-binary lines of Zn x (Sn y Ga 1− y ) 1− x where y = 0.75, 0.50 and 0.25. The excess molar free energy, enthalpy and entropy have been computed by the Darken's treatment of the ternary solutions using published data of the relevant binary solutions and ternary system investigated. Slope–intercept method has been used to compute the partial molar quantities. The activities of tin and gallium are computed from the partial molar excess free energies of three components at 750 K. The activities of all the three components show positive deviation from the Raoult's law. Thermodynamic properties of Sn–Ga binary system have been predicted at 750 K from the ternary data and compared with those published in the literature.

Formation Enthalpy, Free-Energy and Activity Coefficients of Sn-Pb Eutectic Solders

Based on Miedema’s model, the enthalpy of formation, excess free-energy and partial molar excess free-energy of Sn-Pb binary alloy solders were calculated. The model of the activity coefficient for each component in the solders was established. The diagrams of enthalpy of formation, free energy versus composition and activity versus composition and temperature as well as activity coefficients as a function of composition and/or temperature were drawn. And then the relationship between the activity coefficients of elements Sn/Pb in the solders and temperature was obtained. The approaches to reduction in the volatilization of lead at high temperature were proposed from the point of views that the lead pollution to environment results from its chemical activity in the solder alloys.

Density, dynamic viscosity, and derived properties of binary mixtures of 1,4 dioxane with water at T = 298.15 K

Densities and dynamic viscosities for 1,4dioxane with water, at several temperatures T = 298.15 K have been measured over the whole composition range and 0.1 MPa, along with the properties of the pure components. Excess molar volumes, viscosity deviations, and excess free energy of activation for the binary system at the above-mentioned temperature are deduced. The viscosity of a mixture depends on the molecular interactions between the component mixtures with strong interactions between different molecules show positive viscosity deviations and negative excess molar volume confirming recent works that affirmed the water–1,4dioxane cluster formation.

Thermodynamic Investigations of Cd-Zn-Ga Liquid Solutions

Activity of zinc in liquid Cd-Zn-Ga alloys has been measured by electrochemical technique based on molten salt electrolyte galvanic cell in the temperature range 723 to 823 K along three pseudo-binary lines of Zn-(Cd y Ga1−y ), where y = 0.75, 0.50, and 0.25. The excess molar free energy, enthalpy, and entropy were computed by the Darken’s treatment of the ternary solutions using published data of the relevant binary solutions and the ternary system investigated. The excess molar free energy surface of the ternary confirms substantially what one would expect from the knowledge of the corresponding curves of the component binary systems. The excess molar free energy surfaces have the maxima in the Cd-Ga side. The extremum value of molar excess free energy was found to be 3.24 kJ/mol (x Cd = 0.5, x Zn = 0.125, and x Ga = 0.375) at 800 K. The excess molar enthalpy curves have been found to be tilted toward the Zn-Cd and Cd-Ga sides. The extremum value of excess molar enthalpy was found to be 2.58 kJ/mol (x Ga = 0.3 and x Zn = x Cd = 0.35) at 800 K. The excess molar entropy surfaces have the maxima in the Zn-Ga side and minima in the Cd-Ga side. The slope-intercept method was used to compute the partial molar quantities. The activities are computed from the partial molar excess free energy for three components at 800 K. The isoactivity surfaces of the three components are depicted by the isoactivity lines. The activities of all three components show positive deviation from the Raoult’s law. The excess molar free energies of the Cd-Zn-Ga system obtained experimentally are compared with those estimated from the theoretical models.

Physical properties of the ternary system (ethanol + water + 1-butyl-3-methylimidazolium methylsulphate) and its binary mixtures at several temperatures

In this paper, we report experimental densities, dynamic viscosities, and refractive indices and their derived properties of the ternary system (1-butyl-3-methylimidazolium methylsulphate + ethanol + water) at T = 298.15 K and of its binary systems 1-butyl-3-methylimidazolium methylsulphate with ethanol and with water at several temperatures T = (298.15, 313.15, 328.15) K. These physical properties have been measured over the whole composition range and at 0.1 MPa. Excess molar volumes, viscosity deviations, and excess free energy of activation for the binary systems at the abovementioned temperatures, were calculated and fitted to the Redlich–Kister equation to determine the fitting parameters and the root-mean-square deviations and for the ternary systems were calculated and fitted to Cibulka, Singh et al., and Nagata and Sakura equations. The ternary excess properties were predicted from binary contributions using geometrical solution models. Refractive indices were measured from T = 298.15 K over the whole composition range for the binary and ternary systems. The results were used to calculate deviations in the refractive index.

Effect of excess free energy of solvents on the oxidation of methionine by quinolinium fluorochromate: A kinetic study

The oxidation of methionine by quinolinium fluorochromate (QFC) was studied in the presence of chloroacetic acid, in water/organic solvent mixtures of varying excess molar free energy function. The reaction is first order with respect to both QFC and acid. The reaction rates were determined at different temperatures and the activation parameters computed. The rate data was correlated with different solvent parameters using linear multiple regression analysis. From the results, information on the solvent-reactants and the solvent-transition state interactions was obtained. .

EFFECT OF DILUENTS ON CRYSTALLIZATION OF POLY(VINYLIDENE FLUORIDE) AND PHASE SEPARATED STRUCTURE IN A TERNARY SYSTEM via THERMALLY INDUCED PHASE SEPARATION

The phase diagram of a ternary system of PVDF, dibutyl phthalate (DBP) and di(2-ethylhexyl) phthalate (DEHP) was determined in terms of a pseudo binary system with the same polymer concentration and different DBP content in diluent mixture. The experimental results showed that as the DBP content increased in diluent mixture, the phase separation changed from liquid-liquid phase separation to solid-liquid phase separation, and both the cloudy point for L-L phase separation and crystallization temperature shifted to lower temperature. Molar excess free energy of mixing ΔGE implying the estimated interaction between PVDF and diluent mixture was characterized to explain the features in the phase diagram. The effects of DBP content in diluent mixture on crystallization behavior and phase separated structure were investigated. The crystallization of PVDF in system with L-L phase separation was perfect, but the crystallinity was lower relative to the system with only S-L phase separation. The phase separated structures can be controlled successfully by varying the DBP content in diluent mixture as the cooling conditions kept constant.

<b>ACTIVATION PARAMETERS AND EXCESS THERMODYANAMIC FUNCTIONS OF HYDROXAMIC ACIDS IN ACETONE - WATER MIXTURE AT 303.15 K AND 313.15 K: A VISCOMETRIC APPROACH</b>

Experimental values of density and viscosity of N-arylsubstituted hydroxamic acids were evaluated at T = 303.15 K and 313.15 K in acetone-water mixture as a function of their concentration. The properties of solutes were obtained as an intercept of plots C vs η of solutions. Applying these data, viscosity-B-coefficients, activation parameters (Δμ10≠) and (Δμ20≠) and excess thermodynamic functions, viz., excess molar volume (VE), excess viscosity, ηE and excess molar free energy of activation of flow, (GE) were calculated. The value of interaction parameter, d, of Grunberg and Nissan expression have also been calculated and reported. Analysis of these data suggests that specific interactions are present in the system. KEY WORDS: Activation parameters, N-Arylsubstituted hydroxamic acids, Density, Viscosity, Viscosity-B-coefficients, Excess viscosity Bull. Chem. Soc. Ethiop. 2007, 21(3), 379-387.

Spontaneity of reactions of triazine dendric molecules in aqueous medium illustrated with excess viscosities, volumes and free energies

The far-reaching applications of the dendric units – 2,4,6 trichloro-triazine (2,4,6 TCT), triaceto-triazine (2,4,6 TAT), trihydroxy-triazine (2,4,6 THT) and tridiethylmalonate-triazine (2,4,6 TDEMTA) for reactions in an aqueous medium have been assessed in the present study. Some of their fundamental properties, such as density and viscosity, have been measured to calculate the excess volume (V E), viscosity (η E) and molar free activation energy (Δ G E) at 298.15 K for 6.25–10.0 × 10−4 mol kg−1. The positive values of Δ G E for such units suggest their weaker response with water. THT around 3.0 × 10−7 mole fraction shows maximum Δ G E values. The lowest values of Δ G E are recorded for TCT.

Density, dynamic viscosity, and derived properties of binary mixtures of methanol or ethanol with water, ethyl acetate, and methyl acetate at T = (293.15, 298.15, and 303.15) K

Densities and dynamic viscosities for methanol or ethanol with water, ethyl acetate, and methyl acetate at several temperatures T = (293.15, 298.15, and 303.15) K have been measured over the whole composition range and 0.1 MPa, along with the properties of the pure components. Excess molar volumes, viscosity deviations, and excess free energy of activation for the binary systems at the above-mentioned temperatures, were calculated and fitted to the Redlich–Kister equation to determine the fitting parameters and the root-mean-square deviations. UNIQUAC equation was used to correlate the experimental viscosity data. The UNIFAC-VISCO method and ASOG-VISCO method, based on contribution groups, were used to predict the dynamic viscosities of the binary mixtures.