$n_{H_2}=\dfrac{2,24}{22,4}=0,1mol$
$PTHH :$
$Zn+2HCl\to ZnCl_2+H_2↑$
$\text{Cu không phản ứng với HCl}$
$\text{Theo pt :}$
$n_{Zn}=n_{H_2}=0,1mol$
$⇒m_{Zn}=0,1.65=6,5g$
$m_{Cu}=18,4-6,5=11,9g$
$b.n_{H_2}=6,72/22,4=0,3mol$
$PTHH :$
$Fe+2HCl\to FeCl_2+H_2↑$
$\text{Theo pt :}$
$n_{Fe}=n_{H_2}=0,3mol$
$⇒m=m_{Fe}=0,3.56=16,8g$