Faci intai "miu" - ul . Adica numarul masic.
Fe - 56 , S - 32, O - 16
=> miu de Fe2(SO4)3 = 56*2+32*3+16*4*3 = 112+ 96 + 192 = 208 + 192 = 400 g
In 400 g Fe2(SO4)3.......112g Fe.....96g S.......192g O
Dar in 100g Fe2(SO4)3.......x............y...........z
X= 28 % Fe
Y= 24 % S
Z = 48 % O
