The standard enthalpy change of the formation reaction for carbon dioxide CO2 can be calculated using the standard enthalpies of formation for carbon monoxide CO and oxygen gas O2 . The balanced chemical equation for the formation of CO2 from CO and O2 is:CO + 1/2 O2 CO2According to Hess's law, the enthalpy change of the overall reaction is the sum of the enthalpy changes of the individual reactions. In this case, we can write the overall reaction as the sum of the formation reactions for CO and O2, and the formation reaction for CO2:C + 1/2 O2 CO Hf = -110.5 kJ/mol 1/2 O2 O2 Hf = 0 kJ/mol, since O2 is in its standard state Adding these two reactions gives:C + O2 CO2 Hf = ? Now, we can calculate the standard enthalpy change of the formation reaction for CO2:Hf CO2 = Hf CO + Hf 1/2 O2 Hf CO2 = -110.5 kJ/mol + 0 kJ/molHf CO2 = -110.5 kJ/molSo, the standard enthalpy change of the formation reaction for carbon dioxide CO2 is -110.5 kJ/mol.