PTHH: \(Zn+2HCl\rightarrow ZnCl_2+H_2\)
Ta có: \(n_{Zn}=\dfrac{19,5}{65}=0,3\left(mol\right)\)
\(\Rightarrow\left\{{}\begin{matrix}n_{HCl}=0,6\left(mol\right)\\n_{ZnCl_2}=0,3\left(mol\right)=n_{H_2}\end{matrix}\right.\) \(\Rightarrow\left\{{}\begin{matrix}m_{ZnCl_2}=0,3\cdot136=40,8\left(g\right)\\m_{ddHCl}=\dfrac{0,6\cdot36,5}{20\%}=109,5\left(g\right)\\m_{H_2}=0,3\cdot2=0,6\left(g\right)\end{matrix}\right.\)
\(\Rightarrow C\%_{ZnCl_2}=\dfrac{40,8}{19,5+109,5-0,6}\cdot100\%\approx37,78\%\)