Hydrogenation of benzene is given by C6H6+3H2⟶C6H12⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅(a) Enthalpies are given for, C6H6+15∕2O2⟶6CO2+3H2O;∆H=x⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅(b) C6H12+9O2⟶6CO2+6H2O;⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅(c) ∆H=y\H2+1∕2O2⟶H2;∆H=z⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅(d) Reaction (a) =(b)−(c)+3(d) , ∴∆H of a =x−y+3z