scholarly journals Calculation of the Vapour Pressure of Organic Molecules by Means of a Group-Additivity Method and their Resultant Gibbs Free Energy and Entropy of Vaporization at 298.15K

2021 ◽  
Author(s):  
Rudolf Naef ◽  
William E. Acree Jr.
Keyword(s):  
Experimental Data ◽  
Free Energy ◽  
Correlation Coefficient ◽  
Gibbs Free Energy ◽  
Vapour Pressure ◽  
Organic Molecules ◽  
Group Additivity ◽  
Standard Entropy ◽  
Absolute Deviation ◽  
Entropy Of Vaporization

The calculation of the vapour pressure of organic molecules at 298.15K is presented using a commonly applicable computer algorithm based on the group-additivity method. The basic principle of this method rests on the complete breakdown of the molecules into their constituting atoms, further characterized by their immediate neighbour atoms. The group contributions are calculated by means of a fast Gauss-Seidel fitting algorithm using the experimental data of 2036 molecules from literature. A ten-fold cross-validation procedure has been carried out to test the applicability of this method, which confirmed excellent quality for the prediction of the vapour pressure, expressed in log(pa), with a cross-validated correlation coefficient Q2 of 0.9938 and a standard deviation  of 0.26. Based on these data, the molecules' standard Gibbs free energy G°vap has been calculated. Furthermore, using their enthalpies of vaporization, predicted by an analogous group-additivity approach published earlier, the standard entropy of vaporization S°vap has been determined and compared with experimental data of 1129 molecules, exhibiting excellent conformance with a correlation coefficient R2 of 0.9598, a standard error  of 8.14 J/mol/K and a medium absolute deviation of 4.68%.

scholarly journals Calculation of the Vapour Pressure of Organic Molecules by Means of a Group-Additivity Method and Their Resultant Gibbs Free Energy and Entropy of Vaporization at 298.15 K

Molecules ◽  
2021 ◽  
Vol 26 (4) ◽  
pp. 1045
Author(s):  
Rudolf Naef ◽  
William E. Acree
Keyword(s):  
Experimental Data ◽  
Free Energy ◽  
Correlation Coefficient ◽  
Gibbs Free Energy ◽  
Vapour Pressure ◽  
Organic Molecules ◽  
Group Additivity ◽  
Standard Entropy ◽  
Absolute Deviation ◽  
Entropy Of Vaporization

The calculation of the vapour pressure of organic molecules at 298.15 K is presented using a commonly applicable computer algorithm based on the group-additivity method. The basic principle of this method rests on the complete breakdown of the molecules into their constituting atoms, further characterized by their immediate neighbour atoms. The group contributions are calculated by means of a fast Gauss–Seidel fitting algorithm using the experimental data of 2036 molecules from literature. A ten-fold cross-validation procedure has been carried out to test the applicability of this method, which confirmed excellent quality for the prediction of the vapour pressure, expressed in log(pa), with a cross-validated correlation coefficient Q2 of 0.9938 and a standard deviation σ of 0.26. Based on these data, the molecules’ standard Gibbs free energy ΔG°vap has been calculated. Furthermore, using their enthalpies of vaporization, predicted by an analogous group-additivity approach published earlier, the standard entropy of vaporization ΔS°vap has been determined and compared with experimental data of 1129 molecules, exhibiting excellent conformance with a correlation coefficient R2 of 0.9598, a standard error σ of 8.14 J/mol/K and a medium absolute deviation of 4.68%.

scholarly journals Revision and Extension of a Generally Applicable Group-Additivity Method for the Calculation of the Standard Heat of Combustion and Formation of Organic Molecules

Molecules ◽  
2021 ◽  
Vol 26 (20) ◽  
pp. 6101
Author(s):  
Rudolf Naef ◽  
William E. Acree
Keyword(s):  
Standard Deviation ◽  
Correlation Coefficient ◽  
Organic Molecules ◽  
Heat Of Formation ◽  
Group Additivity ◽  
Absolute Deviation ◽  
Complete Breakdown ◽  
Validation Procedure ◽  
Heats Of Combustion ◽  
Fold Cross Validation

The calculation of the heats of combustion DH°c and formation DH°f of organic molecules at standard conditions is presented using a commonly applicable computer algorithm based on the group-additivity method. This work is a continuation and extension of an earlier publication. The method rests on the complete breakdown of the molecules into their constituting atoms, these being further characterized by their immediate neighbor atoms. The group contributions are calculated by means of a fast Gauss–Seidel fitting calculus using the experimental data of 5030 molecules from literature. The applicability of this method has been tested by a subsequent ten-fold cross-validation procedure, which confirmed the extraordinary accuracy of the prediction of DH°c with a correlation coefficient R2 and a cross-validated correlation coefficient Q2 of 1, a standard deviation σ of 18.12 kJ/mol, a cross-validated standard deviation S of 19.16 kJ/mol, and a mean absolute deviation of 0.4%. The heat of formation DH°f has been calculated from DH°c using the standard enthalpies of combustion for the elements, yielding a correlation coefficient R2 for DH°f of 0.9979 and a corresponding standard deviation σ of 18.14 kJ/mol.

scholarly journals Kinetics and thermodynamic properties related to the drying of 'Cabacinha' pepper fruits

2016 ◽  
Vol 20 (2) ◽  
pp. 174-180 ◽  
Author(s):  
Hellismar W. da Silva ◽  
Renato S. Rodovalho ◽  
Marya F. Velasco ◽  
Camila F. Silva ◽  
Luís S. R. Vale
Keyword(s):  
Experimental Data ◽  
Activation Energy ◽  
Free Energy ◽  
Thermodynamic Properties ◽  
Gibbs Free Energy ◽  
Removal Rate ◽  
Effective Diffusion ◽  
Drying Time ◽  
Three Samples ◽  
Different Temperatures

ABSTRACT The objective of this study was to determine and model the drying kinetics of 'Cabacinha' pepper fruits at different temperatures of the drying air, as well as obtain the thermodynamic properties involved in the drying process of the product. Drying was carried out under controlled conductions of temperature (60, 70, 80, 90 and 100 °C) using three samples of 130 g of fruit, which were weighed periodically until constant mass. The experimental data were adjusted to different mathematical models often used in the representation of fruit drying. Effective diffusion coefficients, calculated from the mathematical model of liquid diffusion, were used to obtain activation energy, enthalpy, entropy and Gibbs free energy. The Midilli model showed the best fit to the experimental data of drying of 'Cabacinha' pepper fruits. The increase in drying temperature promoted an increase in water removal rate, effective diffusion coefficient and Gibbs free energy, besides a reduction in fruit drying time and in the values of entropy and enthalpy. The activation energy for the drying of pepper fruits was 36.09 kJ mol-1.

scholarly journals Thermodynamically Consistent Estimation of Gibbs Free Energy from Data: Data Reconciliation Approach

2018 ◽  
Author(s):  
Saman Salike ◽  
Nirav Bhatt
Keyword(s):  
Experimental Data ◽  
Free Energy ◽  
Gibbs Free Energy ◽  
Measurement Errors ◽  
Optimization Problems ◽  
Data Reconciliation ◽  
Group Contributions ◽  
Free Energies ◽  
Consistent Estimation ◽  
Gibbs Energies

AbstractMotivationThermodynamic analysis of biological reaction networks requires the availability of accurate and consistent values of Gibbs free energies of reaction and formation. These Gibbs energies can be measured directly via the careful design of experiments or can be computed from the curated Gibbs free energy databases. However, the computed Gibbs free energies of reactions and formations do not satisfy the thermodynamic constraints due to the compounding effect of measurement errors in the experimental data. The propagation of these errors can lead to a false prediction of pathway feasibility and uncertainty in the estimation of thermodynamic parameters.ResultsThis work proposes a data reconciliation framework for thermodynamically consistent estimation of Gibbs free energies of reaction, formation and group contributions from experimental data. In this framework, we formulate constrained optimization problems that reduce measurement errors and their effects on the estimation of Gibbs energies such that the thermodynamic constraints are satisfied. When a subset of Gibbs free energies of formations is unavailable, it is shown that the accuracy of their resulting estimates is better than that of existing empirical prediction methods. Moreover, we also show that the estimation of group contributions can be improved using this approach. Further, we provide guidelines based on this approach for performing systematic experiments to estimate unknown Gibbs formation energies.AvailabilityThe MATLAB code for the executing the proposed algorithm is available for free on the GitHub repository:https://github.com/samansalike/[email protected]

Standard thermodynamic transfer functions from water to water + acetone mixtures for a n-nonylcarbon chain attached to different ionic groups

1978 ◽  
Vol 56 (23) ◽  
pp. 2940-2946 ◽  
Author(s):  
Raymond Bury ◽  
Claude Treiner
Keyword(s):  
Free Energy ◽  
Gibbs Free Energy ◽  
Standard Enthalpy ◽  
Transfer Functions ◽  
Mixed Solvents ◽  
Standard Entropy ◽  
Standard Gibbs Free Energy ◽  
Ionic Groups ◽  
Solvent Molecules ◽  
Energy Of Transfer

The standard enthalpy of transfer of trimethyldecylammonium bromide, tetramethylammonium bromide, methyl and decylsodium sulfate have been determined from water to water + acetone mixtures from calorimetric measurements at 298.15 K. The standard entropy function has been calculated using standard Gibbs free energy of transfer data for the same compounds. It is shown that the standard enthalpy and entropy of transfer of a n-nonylhydrocarbon chain attached to the sulfate or to the trimethylammonium groups are quite different whereas the standard Gibbs free energy functions are practically equal in the mixed solvents. It is concluded that the sign of the charge on the ionic groups is responsible for this behaviour and that the influence of this effect extends to a large number of solvent molecules. It is suggested that a similar effect may contribute to the standard enthalpy of so called reference ions: e.g. tetraphenylboron ion casting some doubt on the reliability of these extrathermodynamic approaches at least in mixed solvents, as far as the standard enthalpy function is concerned.

scholarly journals A Gibbs free energy minimization based model for liquid–liquid equilibrium calculation of a system containing oil, brine, and surfactant

2020 ◽  
Vol 75 ◽  
pp. 17
Author(s):  
Mostafa Hosseini ◽  
Amir H. Mohammadi
Keyword(s):  
Experimental Data ◽  
Free Energy ◽  
Gibbs Free Energy ◽  
Thermodynamic Modeling ◽  
Sodium Dodecyl ◽  
Binary Interaction ◽  
Ionic Surfactant ◽  
Liquid Equilibrium ◽  
Uniquac Model ◽  
Binary Interaction Parameters

Accurate and reliable phase equilibrium calculations of microemulsion systems are of great importance. This study deals with the thermodynamic modeling of Liquid–Liquid Equilibrium (LLE) of a system including oil (n-decane), brine (containing CaCl2 salt), and ionic surfactant (sodium dodecyl sulfonate). Two models of UNIQUAC and UNIQUAC + Debye–Hückel were used for thermodynamic calculations. The LLE experimental data were utilized to estimate the binary interaction parameters of UNIQUAC model and the adjustable parameter, b, of the Debye–Hückel model. The thermodynamic model calculates the microemulsion phase’s compositions by minimizing the Gibbs free energy of the LLE system using a combination of genetic algorithm and fmincon function in order to prevent local minima. The thermodynamic modeling results show an appropriate agreement with the experimental data. Accordingly, the presented model of this study can be used as a suitable method to investigate the liquid–liquid equilibrium of systems containing oil, water, and surfactant.

scholarly journals Thermodynamic insight into the growth of nanoscale inclusion of Al-deoxidation in Fe–O–Al melt

2020 ◽  
Vol 10 (1) ◽  
Author(s):  
Hong Lei ◽  
Yuanyou Xiao ◽  
Guocheng Wang ◽  
Hongwei Zhang ◽  
Wei Jin ◽  
...  
Keyword(s):  
Experimental Data ◽  
Free Energy ◽  
Gibbs Free Energy ◽  
Liquid Iron ◽  
Reaction Products ◽  
Straight Line ◽  
Nano Alumina ◽  
Increasing Temperature ◽  
The Relationship ◽  
Insight Into

Abstract Products of Al-deoxidation reaction in iron melt are the most common inclusions and play an important effect on steel performance. Understanding the thermodynamics on nano-alumina (or nano-hercynite) is very critical to explore the relationship between Al-deoxidation reaction and products growth in iron melt. In present study, a thermodynamic modeling of nano-alumina inclusions in Fe–O–Al melt has been developed. The thermodynamic results show that the Gibbs free energy changes for the formation of nano-Al2O3 and nano-FeAl2O4 decrease with the increasing size and increase with the increasing temperature. The Gibbs free energy changes for transformation of nano-Al2O3 into bulk-Al2O3 increase with the increasing size and temperature. The thermodynamic curve of nano-alumina (or nano-hercynite) and the equilibrium curve of bulk-alumina (or bulk-hercynite) obtained in this work are agree with the published experimental data of Al-deoxidation equilibria in liquid iron. In addition, the thermodynamic coexisting points about Al2O3 and FeAl2O4 in liquid iron are in a straight line and coincide with the various previous data. It suggested that these scattered experimental data maybe in the different thermodynamic state of Al-deoxidized liquid iron and the reaction products for most of the previous Al-deoxidation experiments are nano-alumina (or nano-hercynite).

SORPTION OF NICKEL (II) IONS BY CHELATING RESIN WITH IMINODIACETATE FUNCTIONALITY

2019 ◽  
Vol 62 (11) ◽  
pp. 63-71
Author(s):  
Vasilii R. Kurdiumov ◽  
Gennady I. Maltsev ◽  
Konstantin L. Timofeev
Keyword(s):  
Experimental Data ◽  
Activation Energy ◽  
Free Energy ◽  
Gibbs Free Energy ◽  
Sorption Process ◽  
Internal Diffusion ◽  
Static Exchange Capacity ◽  
Activation Process ◽  
Kinetic Curves ◽  
Spontaneous Course

The regularities of sorption of nickel (II) ions from a monocomponent system on macroporous weakly acidic cationite Lewatit MonoPlus TP 207 were studied. Sorption isotherms were obtained. It is shown that the extraction process can be fairly reliably described by Langmuir and Freundlich equations. The static exchange capacity (SEC) of the resin was determined. The SEC dependencies at temperatures of 305 and 328 K during the sorption process were revealed. Integral kinetic curves were obtained. It is defined that the equilibrium concentration of nickel (II) ions is reached about 13 times faster with temperature increase from 305 to 328 K. The experimental data were processed using equations that take into account the influence of external, internal diffusion, "sorbent-sorbate" and "sorbate-sorbate" chemical interactions. It was found that the main limiting stage of sorption of nickel (II) ions is the internal diffusion. The values of external and internal diffusion rate constants at the indicated temperatures were determined. The kinetic curves were processed by pseudo first and pseudo second order models, which satisfactorily describe the experimental data. According to transition-state theory the thermodynamic characteristics of the activation process (activation energy, entropy, enthalpy, and Gibbs free energy) were calculated. Relatively low activation energy indicates the decisive contribution of diffusion in the process of sorption of nickel (II) ions. Positive entropy is the evidence of nickel hydration shells destruction during the sorption process. Positive enthalpy proves an endothermic nature of interaction of nickel (II) ions and ionogenic groups. Negative Gibbs free energy witnesses to spontaneous course of the reaction in the forward direction. For known values of stability constants the contents of nickel ionic forms and SEC’s were calculated in terms of pH value. Nickel extraction from solution increases with the appearance of singly-charged NiOH+ ions in the pH range from 8 to 9.

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