$n_{HCl}=21,9/36,5=0,6mol$
$PTHH :$
$Fe+2HCl\to FeCl_2+H_2$
$Zn+2HCl\to ZnCl_2+H_2$
Gọi $n_{Fe}=a;n_{Zn}=b$
$\textrm{Ta có :}$
$m_{hh}=56a+65b=17,7g$
$n_{HCl}=2a+2b=0,6mol$
$\textrm{Ta có hpt :}$
$\left\{\begin{matrix}
56a+65b=17,7 & \\
2a+2b=0,6 &
\end{matrix}\right.$
$⇔\left\{\begin{matrix}
a=0,2 & \\
b=0,1 &
\end{matrix}\right.$
$a/\%m_{Fe}=\dfrac{0,2.56.100\%}{1,7}=63,28\%$
$\%m_{Zn}=100\%-63,28\%=36,72\%$
$b/V_{H_2}=22,4.(0,2+0,1)=6,72l$
