Gibbs-Helmholtz equation

Gibbs-Helmholtz equation

[′gibz ′helm‚hōlts i‚kwā·zhən]

(physical chemistry)

An expression for the influence of temperature upon the equilibrium constant of a chemical reaction, (d ln K °/ dT) _P = Δ H °/ RT ², where K ° is the equilibrium constant, Δ H ° the standard heat of the reaction at the absolute temperature T, and R the gas constant.

(thermodynamics)

Either of two thermodynamic relations that are useful in calculating the internal energy U or enthalpy H of a system; they may be written U = F-T (∂ F /∂ T) _V and H = G-T (∂ G /∂ T) _P, where F is the free energy, G is the Gibbs free energy, T is the absolute temperature, V is the volume, and P is the pressure.

Any of the similar equations for changes in thermodynamic potentials during an isothermal process.

McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.