To calculate the heat of formation of carbon dioxide CO2 , we need to use the following reaction:C graphite + O2 g CO2 g However, we don't have the heat of formation for CO2 directly. Instead, we have the heat of formation for CO and H2O. We can use Hess's Law to find the heat of formation for CO2 by creating a series of reactions that ultimately give us the desired reaction.First, let's consider the heat of formation reactions for CO and H2O:1 C graphite + 1/2 O2 g CO g Hf = -110.5 kJ/mol2 H2 g + 1/2 O2 g H2O g Hf = -285.8 kJ/molNow, we need to find a reaction that involves CO and H2O and can be combined with the above reactions to give us the desired reaction for CO2 formation. The following reaction can be used:3 CO g + 1/2 O2 g CO2 g H = ?Now, we need to manipulate the given reactions 1 and 2 to obtain reaction 3:1 C graphite + 1/2 O2 g CO g Hf = -110.5 kJ/mol2 Multiply reaction 2 by 2 to cancel out H2 and H2O: 2H2 g + O2 g 2H2O g Hf = 2 -285.8 kJ/mol = -571.6 kJ/molNow, add reactions 1 and 2:C graphite + 1/2 O2 g + 2H2 g + O2 g CO g + 2H2O g Now, subtract reaction 3 from the combined reaction:C graphite + 1/2 O2 g + 2H2 g + O2 g CO g + 2H2O g - [CO g + 1/2 O2 g CO2 g ]This gives us:C graphite + O2 g CO2 g Now, we can find the heat of formation for CO2:Hf CO2 = Hf CO + Hf 2H2O - H CO + 1/2 O2 Hf CO2 = -110.5 kJ/mol + -571.6 kJ/mol - H CO + 1/2 O2 Solving for H CO + 1/2 O2 :H CO + 1/2 O2 = -110.5 kJ/mol - -571.6 kJ/mol H CO + 1/2 O2 = 461.1 kJ/molNow, we can find the heat of formation for CO2:Hf CO2 = -110.5 kJ/mol + -571.6 kJ/mol - 461.1 kJ/molHf CO2 = -393.5 kJ/molSo, the heat of formation of carbon dioxide CO2 is -393.5 kJ/mol.