FeCl3
raport atomic=r.a.=1Fe:3Cl=1:3
raport de masa=r.m.=AFe:3ACl=56:3.35,5=56:106,5
M=masa moleculara
M=56+106,5=162,5
162,5 gFeCl3-----------1mol FeCl3
Compozitie procentuala
MFeCl3=162,5
162,5 g FeCl3----------56 gFe-----------106,5 g Cl
100 g FeCl3--------------x ------------------y
x=100.56:162,5=34,46 la suta Fe
y=100.106,5:162,5=65,53 la suta Cl