Answer
290.7 kJ
Work Step by Step
$\Delta H^{o}_{rxn}=\Sigma n_{p}\Delta H_{f}^{o}(products)-\Sigma n_{r}\Delta H_{f}^{o}(reactants)$
$=[2(\Delta H^{o}_{f,\,Cr(s)})+3(\Delta H^{o}_{f,\,CO_{2}(g)})]-[1(\Delta H^{o}_{f,\,Cr_{2}O_{3}(s)})+3(\Delta H^{o}_{f,\,CO(g)})]$
$=[2(0)+3(-393.5\,kJ)]-[1(-1139.7\,kJ)+3(-110.5\,kJ)]$
$= 290.7\,kJ$
