Respuesta :
Answer:
Oxygen (O₂) will have ΔHf equal to 0.0 kJ.
Explanation:
The enthalpy of formation of elements in their native state is considered to be zero. Oxygen in nature occurs as O₂, so its enthalpy of formation will be zero.
the other given species are not elements, they are compounds.
CO and CO₂ both are compounds so they cannot have enthalpy of formation equal to zero.