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The standard Gibbs free energy of formation (G f °) of a compound is the change of Gibbs free energy that accompanies the formation of 1 mole of a substance in its standard state from its constituent elements in their standard states (the most stable form of the element at 1 bar of pressure and the specified temperature, usually 298.15 K or 25 °C).
[1] [2] The word hydrophobic literally means "water-fearing", and it describes the segregation of water and nonpolar substances, which maximizes the entropy of water and minimizes the area of contact between water and nonpolar molecules. In terms of thermodynamics, the hydrophobic effect is the free energy change of water surrounding a solute. [3]
In thermodynamics, the Gibbs free energy (or Gibbs energy as the recommended name; symbol ) is a thermodynamic potential that can be used to calculate the maximum amount of work, other than pressure–volume work, that may be performed by a thermodynamically closed system at constant temperature and pressure.
The electrolysis of water in standard conditions requires a theoretical minimum of 237 kJ of electrical energy input to dissociate each mole of water, which is the standard Gibbs free energy of formation of water. It also requires thermal energy to balance the change in entropy of the reaction.
When both temperature and pressure are held constant, and the number of particles is expressed in moles, the chemical potential is the partial molar Gibbs free energy. [1] [2] At chemical equilibrium or in phase equilibrium, the total sum of the product of chemical potentials and stoichiometric coefficients is zero, as the free energy is at a ...
Free-energy relationship, a relationship in physical organic chemistry; Principle of minimum energy, a thermodynamic formulation based on the second law; Thermodynamic free energy, the energy in a physical system that can be converted to do work, including: Gibbs free energy; Landau free energy (also known as grand potential) Helmholtz free energy
Therefore, only relative free energy values, or changes in free energy, are physically meaningful. The free energy is the portion of any first-law energy that is available to perform thermodynamic work at constant temperature, i.e., work mediated by thermal energy. Free energy is subject to irreversible loss in the course of such work. [1]
Gibbs emphasized that for solids, the surface free energy may be completely different from surface stress (what he called surface tension): [14]: 315 the surface free energy is the work required to form the surface, while surface stress is the work required to stretch the surface. In the case of a two-fluid interface, there is no distinction ...