PTHH: \(Cu+HCl\rightarrow\) Không phản ứng.
\(2Fe+6HCl\rightarrow2FeCl_3+3H_2\\ 0,2mol:0,6mol\leftarrow0,2mol:0,3mol\)
\(n_{H_2}=\dfrac{6,72}{22,4}=0,3\left(mol\right)\)
\(m_{Fe}=0,2.56=11,2\left(g\right)\)
\(\Leftrightarrow m_{Cu}=29,6-11,2=18,4\left(g\right)\)
\(\left\{{}\begin{matrix}\%m_{Fe}=\dfrac{11,2}{29,6}.100\%=37,84\%\\\%m_{Cu}=100\%-37,84\%=62,16\%\end{matrix}\right.\)