Question

Calculate the standard enthalpy of formation, ΔH°f, of carbon dioxide (CO2) gas given the following thermochemical equations:    C(s) + O2(g) → CO2(g)    ΔH°rxn = -393.5 kJ/mol    C(s) + O2(g) → CO(g)    ΔH°rxn = -110.5 kJ/mol    CO(g) + 1/2 O2(g) → CO2(g)    ΔH°rxn = -283.0 kJ/mol Assume that all reactants and products are in their standard states.

Answer 1

The standard enthalpy of formation, Hf, of carbon dioxide  CO2  gas can be determined using the given thermochemical equations. The first equation already represents the formation of CO2 from its elements in their standard states:C s  + O2 g   CO2 g     Hrxn = -393.5 kJ/molIn this case, Hrxn is equal to the standard enthalpy of formation, Hf, of CO2. Therefore, the standard enthalpy of formation of carbon dioxide  CO2  gas is:Hf  CO2  = -393.5 kJ/mol