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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.
Thus, they are essentially equations of state, and using the fundamental equations, experimental data can be used to determine sought-after quantities like G (Gibbs free energy) or H . [1] The relation is generally expressed as a microscopic change in internal energy in terms of microscopic changes in entropy , and volume for a closed system in ...
The Gibbs–Helmholtz equation is a thermodynamic equation used to calculate changes in the Gibbs free energy of a system as a function of temperature. It was originally presented in an 1882 paper entitled " Die Thermodynamik chemischer Vorgänge " by Hermann von Helmholtz .
Helmholtz free energy: A, F = J ML 2 T −2: Landau potential, Landau free energy, Grand potential: Ω, Φ G = J ML 2 T −2: Massieu potential, Helmholtz free entropy: Φ = / J⋅K −1: ML 2 T −2 Θ −1: Planck potential, Gibbs free entropy: Ξ
Differentiating the Euler equation for the internal energy and combining with the fundamental equation for internal energy, it follows that: = + which is known as the Gibbs-Duhem relationship. The Gibbs-Duhem is a relationship among the intensive parameters of the system.
A thermodynamic potential (or more accurately, a thermodynamic potential energy) [1] [2] is a scalar quantity used to represent the thermodynamic state of a system.Just as in mechanics, where potential energy is defined as capacity to do work, similarly different potentials have different meanings.
Several free energy functions may be formulated based on system criteria. Free energy functions are Legendre transforms of the internal energy. The Gibbs free energy is given by G = H − TS, where H is the enthalpy, T is the absolute temperature, and S is the entropy. H = U + pV, where U is the internal energy, p is the pressure, and V is the ...
The differential form of Helmholtz free energy is = = (), = From symmetry of second derivatives = and therefore that = The other two Maxwell relations can be derived from differential form of enthalpy = + and the differential form of Gibbs free energy = in a similar way.