2Al + 3H2SO4 --->Al2(SO4)3 + 3H2
x --->3/2x ---->1/2x --->3/2x
Fe + H2SO4 --->FeSO4 + H2
y -->y ---->y ------> y
m hỗn hợp Al và Fe=7-1,5=5.5g
nH2=4.48/22.4=0.2
HPT 3/2x+y=0.2
27x+56y=5.5
==> x= 0,1 y=0,05
%Cu=1,5.100/7=21,43%
%Al=(0,1.27).100/7=38.57%
%Fe=100% - (%Cu+%Al)=40%