Enthalpy of hydrogenation of cyclohexene =−119.5kJ∕mol ∴ Calculated enthalpy of benzene =3×(−119.5) =−358.5kJ∕mol Resonance energy of benzene =−150.4kJ∕mol As we know, Actual value of enthalpy = Calculated enthalpy - Resonance energy ∴ Actual value of enthalpy =(−358.5)−(−150.4) =−208.1kJ∕mol Hence, the enthalpy of hydrogenation of benzene is −208.1kJ∕mol.