Question

Write Gibbs-Helmholtz Equation.

Answer 1

Hint: It is a thermodynamic equation. It is used for calculating changes in the Gibbs energy of a system as a function of temperature. This equation states that whenever the change in $G/T$ ratio at constant pressure which results from an infinitesimally small change in temperature is a factor $H/T$ .This equation is named after Josiah Williard Gibbs and Herman von Helmholtz.

Complete step by step answer:
Gibbs-Helmholtz equation is used to determine the changes in Gibbs energy of a system as a function of temperature.
The Equation is, ${\left( {\partial \left( {G/T} \right)/\partial T} \right)_P} = - H/{T^2}$
Where $H$ represents the enthalpy, $T$ is the absolute temperature and $G$ represents the Gibbs free energy of the system all at constant pressure. This equation is used to find the changes in Gibbs energy.

Additional information: Gibbs free energy: It is defined as the energy which is associated with a chemical reaction that can be used to do work.
  The equation for free Gibbs energy is,$\vartriangle G = \vartriangle H - T\vartriangle S$ , Where $\vartriangle S$ is the entropy change, $T$ is the temperature and $\vartriangle G$ is the free Gibbs energy. Gibbs free energy tells us whether a reaction is spontaneous or non spontaneous if $\vartriangle G$ is negative reaction is spontaneous and when $\vartriangle G$ is positive reaction is non spontaneous.
Enthalpy: It is the sum of internal energy and product of the pressure and volume.
The formula for enthalpy is from the above statement,$H = U + PV$ , where $H$ is the enthalpy, $U$ is the internal energy, $P$ is the pressure and $V$ is the volume.

Note:For determining the spontaneity of the reaction always look for Gibbs free energy whether it is positive or negative. If it is positive then reaction is not spontaneous and if it is negative then the reaction is spontaneous.
$\Delta G > 0$ (Chemical reaction is nonspontaneous.)
$\Delta G < 0$ (Chemical reaction is spontaneous.)
$\Delta G = 0$ (Chemical reaction is in equilibrium.)