Answer
$\Delta H^o = - 556.72kJ$
Work Step by Step
$\Delta H^o_f : FeO(s) = -271.9$ $ kj/mol$
$\Delta H^o_f : O_2(g) = 0$ $ kj/mol$
$\Delta H^o_f : Fe_2O_3(s) = -822.16$ $ kj/mol$
$4FeO(s) + O_2(g) --> 2Fe_2O_3(s)$
$\Delta H^o = (2*(-822.16)) - (4*(-271.9) + 0)$
$\Delta H^o = -1644.32 - (-1087.6)$
$\Delta H^o = - 556.72 kJ$
