Question

What is the enthalpy for reaction 1 reversed? reaction 1 reversed: co2→co + 12o2 express your answer numerically in kilojoules per mole?

Answer 1

The enthalpies of formation of each of the compound involved in the chemical reaction presented above are given below:

CO2: -393.5 kJ/mol
CO: -99 kJ/mol
O2: 0 kJ/mol

As observed O2 will not have enthalpy of formation as it is a pure substance. 

To calculate for the enthalpy of reaction,
   enthalpy of formation of products - enthalpy of formation of reactants
= (-99 kJ/mol) - (-393.5 kJ/mol)
    = 294.5 kJ/mol

ANSWER: 294.5 kJ/mol