Chapter 5 - Thermochemistry - Exercises - Page 207: 5.73b

$H^o = 37.07 kJ$

$H^o_f : Mg(OH)_2 (s) = -924.7 kJ/mol$ $H^o_f : MgO (s) = -601.8 kJ/mol$ $H^o_f : H_2O(l) = -285.83 kJ/mol$ $Mg(OH)_2(s) --> MgO(s) + H_2O(l)$ $H^o = [-601.8 + (-285.83)] - [-924.7]$ $H^o = -887.63 + 924.7$ $H^o = +37.07 kJ$