The bond dissociation energy of methane CH4 is the energy required to break all the C-H bonds in one mole of methane molecules. In the given reaction, one mole of methane CH4 dissociates into one mole of carbon C and four moles of hydrogen H atoms. The enthalpy change of the reaction H is given as 1665 kJ/mol. This value represents the total energy required to break all the C-H bonds in one mole of methane molecules.Since there are four C-H bonds in one methane molecule, we can calculate the bond dissociation energy of a single C-H bond by dividing the enthalpy change by the number of bonds:Bond dissociation energy of C-H bond = H / number of C-H bonds = 1665 kJ/mol / 4= 416.25 kJ/molTherefore, the bond dissociation energy of a single C-H bond in methane CH4 at standard conditions 25C and 1 atm is 416.25 kJ/mol.