The bond dissociation energy is the energy required to break a bond, so we need to find the energy required to break the carbon-carbon single bond in ethane. The given enthalpy change for the reaction C2H6 g 2CH3 g is -84.68 kJ/mol. Since the reaction is exothermic negative enthalpy change , the bond dissociation energy will be the opposite of the enthalpy change.Bond dissociation energy of C-C single bond in ethane = +84.68 kJ/mol