Given:

$H=-127k\frac{J}{m}ol$ for MgO$(s)+2HCl(aq)MgC{l}_2(aq)+H_{2}O(l)$

$H_f=-601\mathrm{.}7k\frac{J}{m}ol$ for $Mg(s)+\frac{1}{2}{O}_2(g)$MgO$(s)$

$H_f=-285\mathrm{.}8k\frac{J}{m}ol$ for $H_2(g)+\frac{1}{2}{O}_2(g)H_{2}O(l)$

$H_f=0\mathrm{.}00k\frac{J}{m}ol$ for $Mg(s)$ and $H_2(g)$

Calculate the $H{?}_{rxn}($in kJ$)$ for

$Mg(s)+2HCl(aq)MgC{l}_2(aq)+H_2(g)$

Answer: