To calculate the bond enthalpy of the carbon-carbon bond in ethane, we need to consider the enthalpy change for the reaction C2H6 g 2CH3 g , which is given as +84.7 kJ/mol.In this reaction, one molecule of ethane C2H6 is broken down into two methyl radicals CH3 . The only bond being broken in this process is the carbon-carbon C-C bond in ethane. Therefore, the enthalpy change for this reaction corresponds to the bond enthalpy of the C-C bond in ethane.Thus, the bond enthalpy for the C-C bond in ethane is +84.7 kJ/mol.