The bond enthalpy of a carbon-hydrogen C-H bond in methane CH4 can be determined by dividing the energy required to break a mole of C-H bonds in methane by the number of C-H bonds in a molecule of methane.Methane has 4 C-H bonds in its structure. Given that the energy required to break a mole of C-H bonds in methane is 413 kJ/mol, we can calculate the bond enthalpy as follows:Bond enthalpy of C-H bond = Energy required to break a mole of C-H bonds / Number of C-H bonds in a molecule of methane Bond enthalpy of C-H bond = 413 kJ/mol / 4Bond enthalpy of C-H bond = 103.25 kJ/molTherefore, the bond enthalpy of a carbon-hydrogen C-H bond in methane CH4 is 103.25 kJ/mol.