2Al + Fe2O3 ---> 2Fe+Al2O3
2*27g 160g 102 g
x g 260g y g
x=260*2*27/160=......
y=260*102/160=165,75 g Al2O3
3H2SO4+ Al2O3----> Al2(SO4)3 + 3H2O
3*98 g 102 g
z g 165,75
z=.........g si reprezinta md din formula c=md*100/ms ==>ms=md*100/c
-se cunoaste md si c%