Standard molar enthalpies of formation of cyclohexane(l) and benzene (l)  at  25°C are -156 and +49KJ  ${\mathrm{mol}}^{-1}$ respectively. The standard enthalpy of hydrogenation of cyclohexene (l) at 25°C is $-119\mathrm{KJ}/\mathrm{mol}$ using data calculate the resonance energy of benzene.

By using above data,theoretical heat of formation of benzene is calculated

$\begin{array}{l}6\mathrm{C}+6{\mathrm{H}}_2\to {\mathrm{C}}_6{\mathrm{H}}_{12\left(t\right)};\Delta {\mathrm{H}}_1=-156{\mathrm{KJmol}}^{-1}\\ {\mathrm{C}}_6{\mathrm{H}}_{10}+{\mathrm{H}}_2\to {\mathrm{C}}_6{\mathrm{H}}_{12};\Delta {\mathrm{H}}_2=-119\mathrm{KJmol}\end{array}$

$\therefore$heat of hydrogenation of benzene 3 times that of heat of hydrogenation of cyclohexene, benzene involves reduction of 3 double bonds.

$\therefore {\mathrm{C}}_6{\mathrm{H}}_6+3{\mathrm{H}}_2\to {\mathrm{C}}_6{\mathrm{H}}_{12\left(1\right)};\Delta {\mathrm{H}}_3=3(-119)=-357{\mathrm{KJmol}}^{-1}$

$\begin{array}{l}6{\mathrm{C}}_{\mathrm{s}}+3{\mathrm{H}}_2\to {\mathrm{C}}_6{\mathrm{H}}_6;\Delta \mathrm{H}=?\\ \Delta \mathrm{H}=\Delta {\mathrm{H}}_1-\Delta {\mathrm{H}}_3\\ =+201{\mathrm{KJmol}}^{-1}\end{array}$

$\begin{array}{l}\therefore \text{ resonance energy }={\left({\Delta }_{j}H\right)}_{\exp }-{\left({\Delta }_{f}H\right)}_{ca}\\ =49-201\\ =-152{\mathrm{KJmol}}^{-1}\end{array}$