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 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.

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.

Thermodynamics of transfer of Ph4C; scaled-particle theory and the Ph4As+/Ph4B− assumption for single ions

1979 ◽  
Vol 57 (15) ◽  
pp. 2004-2009 ◽  
Author(s):  
Michael H. Abraham ◽  
Asadollah Nasehzadeh
Keyword(s):  
Free Energy ◽  
Total Free Energy ◽  
Scaled Particle Theory ◽  
Free Energies ◽  
Particle Theory ◽  
Free Energy Of Transfer ◽  
Enthalpy And Entropy ◽  
Interaction Term ◽  
Energy Of Transfer ◽  
Entropy Of Transfer

Free energies of transfer of Ph4C from acetonitrile to 20 other solvents have been calculated from literature data. The contribution of the cavity term to the total free energy has been obtained from scaled-particle theory and Sinanoglu–Reisse–Moura Ramos theory. It is shown that there is little connection between the cavity term and the total free energy of transfer, and that there must be, in general, a large interaction term. If the latter is important for transfer of Ph4C, we argue that it must also be important for transfer of the ions Ph4As+ and Ph4B−. Previous suggestions that the interaction term is zero for transfer of these two ions are thus seen to be unreasonable. We also show, for six solvents, that the interaction term for Ph4C is very large in terms of enthalpy and entropy, and that scaled-particle theory seems not to apply to transfers of Ph4C between pure organic solvents.The free energy, enthalpy, and entropy of transfer of Ph4As+ = Ph4B− have been calculated by dividing the total transfer values into neutral and electrostatic contributions; reasonable agreement is obtained between calculated and observed values.

A Mnemonic Scheme for Thermodynamics

MRS Bulletin ◽  
2009 ◽  
Vol 34 (2) ◽  
pp. 92-94 ◽  
Author(s):  
J.-C. Zhao
Keyword(s):  
Free Energy ◽  
Internal Energy ◽  
Gibbs Free Energy ◽  
Maxwell Equations ◽  
Helmholtz Free Energy ◽  
State Variables ◽  
Max Born ◽  
Thermodynamic Potentials ◽  
Classical Thermodynamics ◽  
Thermodynamic Equations

AbstractA mnemonic scheme is presented to help recall the equations in classical thermodynamics that connect the four state variables (temperature, pressure, volume, and entropy) to the four thermodynamic potentials (internal energy, Helmholtz free energy, enthalpy, and Gibbs free energy). Max Born created a square to help recall the thermodynamic equations. The new scheme here separates the Max Born square into two squares, resulting in easier recalling of several sets of equations, including the Maxwell equations, without complicated rules to remember the positive or negative signs.

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.

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