To calculate the standard enthalpy of formation of methane CH4 , we need to consider the bond dissociation energies of the reactants and products involved in the formation reaction. The formation reaction for methane can be written as:C graphite + 2 H2 g CH4 g Now, we need to calculate the energy required to break the bonds in the reactants and the energy released when the bonds in the product are formed.For the reactants, we have:1 C-C bond in graphite: We don't need to consider this bond since it's not broken in the formation of methane.2 H-H bonds in H2: 2 436 kJ/mol = 872 kJ/molFor the product, we have:4 C-H bonds in CH4: 4 413 kJ/mol = 1652 kJ/molNow, we can calculate the standard enthalpy of formation Hf using the following equation:Hf = Bond energies of reactants - Bond energies of products Hf = 872 kJ/mol - 1652 kJ/mol = -780 kJ/molSo, the standard enthalpy of formation of methane CH4 is -780 kJ/mol.