$2Al + C{r_2}{O_3} \to A{l_2}{O_3} + 2Cr$
\(\Delta H=\Sigma \Delta_f H^{\circ}_{products}\) \(-\Sigma \Delta_1 H^{\circ}_{recectants}\)
\(=\left|\Delta_r H^{\circ} _{ Al _2 O _3}+2 \Delta_f H _{ Cr }^{}\right|-\left[2 \Delta_1 H _{ Al }^0+\Delta_1 H _{ Cr _2 O_3}^0 \mid\right.\)
\(=\mid-1596+2(0)]-|2(0)+(-1134)|\)
\(=-462\, kJ\)