Question 26
Energy ChangesFe2O3(s) + 2Al(s) → Al2O3(s) + 2Fe(s). If the heats of formation of Al2O3 and Fe2O3 are −1670 kJ mol−1 and −822 kJ mol−1 respectively, the enthalpy change in kJ for the reaction is
- A.+2492
- B.+848
- C.−848
- D.−2492.
Show the answer and explanation
Answer: C (−848)
Explanation
ΔH = sum of heats of formation of products − reactants = (−1670) − (−822) = −848 kJ. Elements (Al, Fe) have zero heat of formation.