a,
$Zn+H_2SO_4\to ZnSO_4+H_2$
$Fe+H_2SO_4\to FeSO_4+H_2$
$2Al+3H_2SO_4\to Al_2(SO_4)_3+3H_2$
b,
Gọi $x$, $y$, $z$ là số mol $Zn$, $Fe$, $Al$
$\Rightarrow 65x+56y+27z=48$ $(1)$
$n_{Zn}=1,5n_{Fe}$
$\Rightarrow x-1,5y=0$ $(2)$
$n_{Zn}=0,5n_{Fe}$
$\Rightarrow x-0,5z=0$ $(3)$
$(1)(2)(3)\Rightarrow x=0,3; y=0,2; z=0,6$
$m_{Zn}=0,3.65=19,5g$
$m_{Fe}=0,2.56=11,2g$
$m_{Al}=17,3g$