Answer
$H^o = -68.34kJ$
Work Step by Step
$H^o_f : SiCl_4(l) = -640.1 kj/mol$
$H^o_f : H_2O(l) = -285.83 kj/mol$
$H^o_f : SiO_2(s) = -910.9 kj/mol$
$H^o_f : HCl(g) = -92.3 kj/mol$
$SiCl_4(l) + 2H_2O(l) --> SiO_2(s) + 4HCl(g)$
$H^o = (-910.9 + 4*(-92.3)) - (-640.1 + 2*(-285.83)) $
$H^o = (-1280.1) - (-1211.76)$
$H^o = -68.34 kJ$
