Question

What is the ΔH° for the following reaction (in kJ/mol of reaction exactly as written)?

2 Al (s) + Fe2O3 (s) → Al2O3 (s) + 2 Fe (s)

To solve, use Appendix II in your textbook (containing standard heats of formation).

Answer 1

Standard enthalies of formation of $Fe_2O_3$ = $-822 \ kJ \ mol^{-1}$

Standard enthalies of formation of $Al_2O_3=-1669\ kJ\ mol^{-1}$

Now ,

$$\Delta H^{o}_r=\Sigma(\Delta H^o_{products}-\Delta H^o_{reactants})$$ $$\Delta H^o_r=-1669-(-822)=-847\ kJ\ mol^{-1}$$