${\mathrm{C}}_6{\mathrm{H}}_6+3{\mathrm{H}}_2\rightleftharpoons {\mathrm{C}}_6{\mathrm{H}}_{12}, ∆\mathrm{H}=-204 \mathrm{kJ} ;$ Heat of hydrogenation of each C=C (assumed to be) in benzene is [in KJ]

Benzene contains 3 C=C bonds

                                                                                

$\mathrm{C}=\mathrm{C} \mathrm{bond} \mathrm{enthalpy}=-\frac{204}{3}=-68 \mathrm{kJ}/\mathrm{mole} ;$