Question

For a reaction both enthalpy change and entropy change are positive. Under what conditions the reaction will be spontaneous?

Answer 1

Let us consider the equation for gibbs free energy

$\Delta G=\Delta H-T\Delta S$

Where,

$\delta H$ is enthalpy change $\left(KJmo{l}^{-1}\right)$

$T$ is absolute temperature $\left(K\right)$

$\Delta S$ is entropy change $\left(J{K}^{-1}\right)$

For a reaction to be considered spontaneous $\Delta G<0$

Therefore,

$\Delta H-T\Delta S<0$

$\Delta H<T\Delta S$

or

$T>\Delta H\Delta S$