# What is Gibb's Helmholtz equation? Explain with the help of applications.

The Gibbs–Helmholtz equation is a thermodynamic equation used for calculating changes in the Gibbs energy of a system as a function of temperature. It is named after Josiah Willard Gibbs and Hermann von Helmholtz.

$$\begin{array}{l}(\frac{\delta \left ( \frac{G}{T} \right )}{\delta T})_{p}= -\frac{H}{T^{2}}\end{array}$$

H is the enthalpy, T the absolute temperature and G the Gibbs free energy of the system, all at constant pressure p.

### Application of Gibbs–Helmholtz equation

• Calculate ΔHrxn from ΔG and its variation with the temperature at constant pressure
• Calculate ΔGrxn for a reaction at a temperature other than 298K
• Calculate the effect of a temperature change on the equilibrium constant Kp