Answer
$\Delta H^o = -217.52 kJ$
Work Step by Step
$\Delta H^o_f : CaO(s) = -635.5kJ$
$\Delta H^o_f : HCl (g) = -92.3kJ$
$\Delta H^o_f : CaCl_2(s) = -795.8kJ$
$\Delta H^o_f : H_2O(g) = -241.82kJ$
$CaO(s) + 2HCl(g) --> CaCl_2(s) + H_2O(g)$
$\Delta H^o = ((-795.8) + (-241.82)) - ((-635.5) + 2*(-92.3))$
$\Delta H^o = (-1037.62) - (-820.1)$
$\Delta H^o = -217.52 kJ$
