\(PT:Zn+2HCl-\longrightarrow{}ZnCl_2+H_2\)
\(n_{H2}=\frac{V}{24,79}=\frac{4,958}{24,79}=0,2\left(mol\right)\)
\(\Rightarrow n_{Zn}=n_{H2}=0,2\left(mol\right)\)
\(\Rightarrow m_{zn}=nM=0,2.65=13\left(g\right)\)
\(\Rightarrow m_{Cu}=20-13=7\left(g\right)\)
\(\Rightarrow\begin{cases}\%Zn=\frac{13}{20}.100\%=65\%\\ \%Cu=\frac{7}{20}.100=35\%\end{cases}\)