\(\left\{{}\begin{matrix}n_{Mg}=a\left(mol\right)\\n_{MgO}=b\left(mol\right)\end{matrix}\right.\left(a,b>0\right)\\ a.PTHH:Mg+2HCl\rightarrow MgCl_2+H_2\\ a.......................2a.........a..........a\left(mol\right)\\ PTHH:MgO+2HCl\rightarrow MgCl_2+H_2O\\ b.....................2b.............b..............b\left(mol\right)\\ \rightarrow\left\{{}\begin{matrix}95a+95b=47,5\\a=0,2\end{matrix}\right.\Leftrightarrow\left\{{}\begin{matrix}a=0,2\\b=0,3\end{matrix}\right.\\ \rightarrow\left\{{}\begin{matrix}m_{Mg}=0,2.24=4,8\left(g\right)\\m_{MgO}=0,3.40=12\left(g\right)\end{matrix}\right.\\ \)
\(b.m_{HCl}=\left(2a+2b\right).36,5=36,5\left(g\right)\\ m_{ddHCl}=\dfrac{36,5.100}{14,6}=250\left(g\right)\\ m_{ddsau}=250+4,8+12-0,2.2=266,4\left(g\right)\\ C_{\%ddMgCl_2}=\dfrac{47,5}{266,4}.100\approx17,83\%\)
