Question

Calculate the heat of formation of carbon dioxide gas (CO2) given the following bond energies: C=O bond energy is 799 kJ/mol and C-O bond energy is 358 kJ/mol.

Answer 1

To calculate the heat of formation of carbon dioxide gas  CO2 , we need to consider the bond breaking and bond forming processes. In CO2, there are two C=O double bonds. 1. Bond breaking: We need to break one C-O bond and one C=O bond in order to form two C=O bonds in CO2. C-O bond energy = 358 kJ/molC=O bond energy = 799 kJ/molTotal bond breaking energy = 358 kJ/mol + 799 kJ/mol = 1157 kJ/mol2. Bond forming:Now, we need to form two C=O bonds in CO2.2  C=O bond energy = 2  799 kJ/mol = 1598 kJ/molTotal bond forming energy = 1598 kJ/mol3. Heat of formation:Heat of formation = Total bond forming energy - Total bond breaking energyHeat of formation = 1598 kJ/mol - 1157 kJ/mol = 441 kJ/molThe heat of formation of carbon dioxide gas  CO2  is 441 kJ/mol.