How can the enthalpy of the hydrogenation of benzene be measured from its enthalpy of combustion and the enthalpies of combustion of cyclohexane and hydrogen? Make use of Hess's law.  

The energy difference among the formula proposed by Kekulé and the real bonding situation can be estimated by comparing the theoretically estimated and experimentally found enthalpies of hydrogenation for benzene. The enthalpy of hydrogenation of cyclohexene is 120 kJ mol^-1. This value is the energy of hydrogenation of a double bond.