Question

Standard molar enthalpy of formation, Δ_f H^Θ is just a special case of enthalpy of reaction, Δ_r H^Θ. Is the Δ_r H^Θ for the following reaction same as Δ_f H^Θ ? Give reason for your answer.

CaO(s) + CO₂(g) → CaCO₃(s); Δ_f H^Θ = –178.3 kJ mol^–1

Answer 1

No, standard molar enthalpy of formation is the enthalpy of the reaction when 1 mole of a compound is formed from its constituent elements.