scholarly journals Ion hydration free energies and water surface potential in water nano drops: The cluster pair approximation and the proton hydration Gibbs free energy in solution

2019 ◽  
Vol 151 (17) ◽  
pp. 174504 ◽  
Author(s):  
Céline Houriez ◽  
Florent Réal ◽  
Valérie Vallet ◽  
Michael Mautner ◽  
Michel Masella
Keyword(s):  
Free Energy ◽  
Gibbs Free Energy ◽  
Surface Potential ◽  
Water Surface ◽  
Pair Approximation ◽  
Free Energies ◽  
Ion Hydration ◽  
Cluster Pair

Chemical equilibrium and chemical kinetics

2018 ◽  
Author(s):  
Dennis Sherwood ◽  
Paul Dalby
Keyword(s):  
Free Energy ◽  
Equilibrium Constant ◽  
Gibbs Free Energy ◽  
Chemical Kinetics ◽  
Chemical Equilibrium ◽  
First Principles ◽  
Effect Of Temperature ◽  
Total System ◽  
Free Energies

Building on the previous chapter, this chapter examines gas phase chemical equilibrium, and the equilibrium constant. This chapter takes a rigorous, yet very clear, ‘first principles’ approach, expressing the total Gibbs free energy of a reaction mixture at any time as the sum of the instantaneous Gibbs free energies of each component, as expressed in terms of the extent-of-reaction. The equilibrium reaction mixture is then defined as the point at which the total system Gibbs free energy is a minimum, from which concepts such as the equilibrium constant emerge. The chapter also explores the temperature dependence of equilibrium, this being one example of Le Chatelier’s principle. Finally, the chapter links thermodynamics to chemical kinetics by showing how the equilibrium constant is the ratio of the forward and backward rate constants. We also introduce the Arrhenius equation, closing with a discussion of the overall effect of temperature on chemical equilibrium.

scholarly journals Rationalisation of the activities of phenolic (vitamin E-type) antioxidants

2003 ◽  
Vol 17 (4) ◽  
pp. 753-762
Author(s):  
Christopher J. Rhodes ◽  
Thuy T. Tran ◽  
Philip Denton ◽  
Harry Morris
Keyword(s):  
Free Energy ◽  
Vitamin E ◽  
Gibbs Free Energy ◽  
State Theory ◽  
Linear Free Energy Relationship ◽  
Free Energies ◽  
Gibbs Free Energy Change ◽  
Linear Free Energy ◽  
Free Energy Of Activation ◽  
Enthalpy And Entropy

Using Transition-State Theory, experimental rate constants, determined over a range of temperatures, for reactions of vitamin E type antioxidants are analysed in terms of their enthalpies and entropies of activation. It is further shown that computational methods may be employed to calculate enthalpies and entropies, and hence Gibbs Free Energies, for the overall reactions. Within the Linear Free Energy Relationship (LFER) assumption, that the Gibbs Free Energy of activation is proportional to the overall Gibbs Free Energy change for the reaction, it is possible to rationalise, and even to predict, the relative contributions of enthalpy and entropy for reactions of interest, involving potential antioxidants.

Design and Thermodynamic Analysis on One-Step Amination of Benzene to Aniline Systems

2012 ◽  
Vol 550-553 ◽  
pp. 2607-2611
Author(s):  
Chun Hua Yang ◽  
Gang Chen ◽  
Long Zhang
Keyword(s):  
Hydrogen Peroxide ◽  
Free Energy ◽  
Equilibrium Constant ◽  
Gibbs Free Energy ◽  
Driving Force ◽  
Theoretical Basis ◽  
Free Energies ◽  
One Step ◽  
The One ◽  
Further Development

Seven systems of one-step synthesis of aniline were designed, and it was determined which one could occur spontaneously through the calculation of Gibbs free energy of it. Among the seven systems, the Gibbs free energy of the one with ammonia as the aminating agent and hydrogen peroxide as the oxidant was the lowest, thus its process driving force was the largest, that is, .For this system just mentioned above, the standard Gibbs free energies, the equilibrium constant and the equilibrium conversions of benzene under different conditions were discussed ,which was expected to provide a theoretical basis for further development and application of the system.

Effect of mechanical activation on the structure of pulverized coal and iron ore powder

2019 ◽  
Vol 116 (6) ◽  
pp. 624
Author(s):  
Rufei Wei ◽  
Dongwen Xiang ◽  
Hongming Long ◽  
Jiaxin Li ◽  
Qingmin Meng
Keyword(s):  
Free Energy ◽  
Mechanical Activation ◽  
Gibbs Free Energy ◽  
Iron Ore ◽  
Pulverized Coal ◽  
Activation Process ◽  
Free Energies ◽  
Boundary Area ◽  
Particle Sizer ◽  
Storage Energy

Morphologies and structures of pulverized coal and iron ore powder after mechanical activation were studied by SEM, XRD, FTIR and laser particle sizer. The microcrystalline structure of coal was found to be destroyed by mechanical activation via reducing the pile height and number of layers, and the organic structure of coal was altered through the destruction of the ether bond. Mechanical activation led to distortions and dislocations of the crystal lattice of iron ore, decreasing crystallite size, increasing the grain boundary area, and producing an amorphous phase. These increased the Gibbs free energies of dislocations and grain boundaries as well as the surface Gibbs free energy and the amorphization Gibbs free energy, which would eventually increase the energy stored in iron ore called mechanical storage energy. The longer the mechanical activation process, the higher mechanical storage energy for the iron ore will be saved. The amorphization Gibbs free energy is the biggest among the four kinds of Gibbs free energy, accounting for 94.8% ∼ 87.1% of the total storage energy in the mechanical activated iron ore.

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]

Free energy

2018 ◽  
Author(s):  
Dennis Sherwood ◽  
Paul Dalby
Keyword(s):  
Free Energy ◽  
Gibbs Free Energy ◽  
Helmholtz Free Energy ◽  
Chemical Potential ◽  
Free Energies ◽  
Central Concept ◽  
Mathematical Properties ◽  
Closed Systems ◽  
Coupled Reactions ◽  
Enthalpy And Entropy

A critical chapter, explaining how the principles of thermodynamics can be applied to real systems. The central concept is the Gibbs free energy, which is explored in depth, with many examples. Specific topics addressed are: Spontaneous changes in closed systems. Definitions and mathematical properties of Gibbs free energy and Helmholtz free energy. Enthalpy- and entropy-driven reactions. Maximum available work. Coupled reactions, and how to make non-spontaneous changes happen, with examples such as tidying a room, life, and global warming. Standard Gibbs free energies. Mixtures, partial molar quantities and the chemical potential.

scholarly journals GIBBS FREE ENERGY OF NATURAL GAS COMPONENTS FORMATION IN SEDIMENTARY STRATA

2019 ◽  
Vol 2 (179) ◽  
pp. 37-46
Author(s):  
Yuri KHOKHA ◽  
Oleksandr LYUBCHAK ◽  
Myroslava YAKOVENKO
Keyword(s):  
Heat Flux ◽  
Free Energy ◽  
Natural Gas ◽  
Gibbs Free Energy ◽  
Equations Of State ◽  
Carbon Number ◽  
Hydrocarbon Chain ◽  
Heat Fluxes ◽  
Energy Calculation ◽  
Free Energies

The main methods of calculating the composition of geochemical systems in the thermodynamic equilibrium state were considered in the article. It was shown that the basis for such calculations was the determination of the Gibbs Free Energy of each system components at given temperatures and pressures. The methods of Gibbs Free Energy calculation at standard pressure and under conditions that are realized within the sedimentary strata were analyzed. The equations of state for natural gas individual components were selected and their Gibbs Free Energies for heat fluxes ranging from 40 to 100 mW/m2 and depths of 0–20 km were calculated. The results showed that the pressure significantly affects the value of Gibbs Free Energies formation of natural gas components within the sedimentary strata. Changes of the Gibbs Free Energies of natural gas components formation, as a function of depth, subordinated to the same laws for each compound. This regularity was better expressed in more heated areas. It was shown that with depth increasing the Gibbs Free Energy of natural gas components formation first rapidly decreases and reaches its minimum ranging from 2 to 6 km. Moreover, as the value of the heat flux increases, the maximum value of the Gibbs Free Energy of formation of natural gas components, expressed in kilometers, decreases. With further immersion/deepening to depths greater than 6 km, the Gibbs Free Energy of the formation of natural gas components gradually increases, and in areas with greater heat flux, a sharp increase was characteristic, and with less, it was slow and weakly expressed. There is a stability area for hydrocarbon and non-hydrocarbon components of natural gas ranging from 2 to 6 km. With the increase of Carbon number in the hydrocarbon chain, the value of Gibbs Free Energy of the natural gas hydrocarbon components formation decreases, which indicates the presence of a stability zone for heavy natural gas components (it should be expected that oil also) within the depths of 2–6 km.

scholarly journals Evaluation of Stoichiometry, Stability Constants and Gibbs Free Energies of Acetaminophen-Zn (II) complex at Different Temperatures

2020 ◽  
Vol 24 (7) ◽  
pp. 1137-1143
Author(s):  
O.V. Ikpeazu ◽  
I.E. Otuokere ◽  
K.K. Igwe
Keyword(s):  
Free Energy ◽  
Stability Constant ◽  
Gibbs Free Energy ◽  
Stability Constants ◽  
Continuous Variation ◽  
Variation Method ◽  
Ratio Method ◽  
Free Energies ◽  
Different Temperatures ◽  
Continuous Variation Method

Acetaminophen also known as paracetamol, is a drug used in the treatment of pain and fever. It is essentially used for the relief of mild to moderate pain. The presence of phenol and carbonyl oxygen atom enables acetaminophen to behave as a bidentate ligand. The stoichiometry, stability constants and Gibbs free energies of acetaminophen-Zn (II) were determined colorimetrically at 25 and 40 oC using continuous variation and mole  ratio methods. The formation of Zn (II) complex with acetaminophen was studied colorimetrically at an absorption maximum of 630 nm at different temperatures. The data showed that Zn (II) and acetaminophen combine in the molar ratio of 1:1 at pH 7.4 with ionic strength maintained using 0.1M KNO3. Calculated stability constants values were 2.70 x 103 and 2.20 x 103 using continuous variation method and 7.21 x 103 and 7.21 x 103 using mole ratio methods at 25 and 40 oC respectively. Calculated ΔGƟ for the complex were - 1.96 x 104 and -1.98 x 104 J using continuous variation method and -2.2 x 104 J and - 2.31 x 104 J using mole ratio method at 25 and 40 oC respectively. The stability constant and Gibbs free energy results suggested that acetaminophen used in the study is a good chelating agent and can be an efficient antidote in the therapy of Zn (II) overload or poisoning. Keywords: Acetaminophen, Zinc, complex, stability constant, Gibbs free energy.

scholarly journals Absolute ion hydration free energy scale and the surface potential of water via quantum simulation

2020 ◽  
Vol 117 (48) ◽  
pp. 30151-30158
Author(s):  
Yu Shi ◽  
Thomas L. Beck
Keyword(s):  
Free Energy ◽  
Long Range ◽  
Electric Fields ◽  
Surface Potential ◽  
Energy Scale ◽  
Potential Contribution ◽  
Hydration Free Energy ◽  
Ion Hydration ◽  
Ion Distributions ◽  
Interfacial Potential

With a goal of determining an absolute free energy scale for ion hydration, quasi-chemical theory and ab initio quantum mechanical simulations are employed to obtain an accurate value for the bulk hydration free energy of the Na+ion. The free energy is partitioned into three parts: 1) the inner-shell or chemical contribution that includes direct interactions of the ion with nearby waters, 2) the packing free energy that is the work to produce a cavity of size λ in water, and 3) the long-range contribution that involves all interactions outside the inner shell. The interfacial potential contribution to the free energy resides in the long-range term. By averaging cation and anion data for that contribution, cumulant terms of all odd orders in the electrostatic potential are removed. The computed total is then the bulk hydration free energy. Comparison with the experimentally derived real hydration free energy produces an effective surface potential of water in the range −0.4 to −0.5 V. The result is consistent with a variety of experiments concerning acid–base chemistry, ion distributions near hydrophobic interfaces, and electric fields near the surface of water droplets.

Sign in / Sign up

Export Citation Format

Share Document