Question

Zinc reacts with dilute hydochloric acid to give hydrogen at ${17}^{o}C$. The enthalpy of the reaction is $-12.55kJ{mol}^{-1}$ of zinc and entropy change equals $5.0J{K}^{-1}{mol}^{-1}$ for the reaction. Calculate the free energy change and predict whether the reaction is spontaneous or not.

Answer 1

Given $\Delta H=-12.55kJ{mol}^{-1}$
$\Delta S=5.0J{K}^{-1}{mol}^{-1}=0.005kJ{K}^{-1}{mol}^{-1}$
$T=17+273=290K$
Applying $\Delta G=\Delta H-T\Delta S$
$=-12.55-0.005\times 290$
$=-14.00kJ{mol}^{-1}$
since, $\Delta G$ is negative, the reaction will be spontaneous.