Se foloseste relatia : n= m : M in care : n=nr. de moli
m=masa subst . ( g )
M= masa molara ( g/moli )
2,5 moli Al2O3 ------> g
n=m:M
m=n .M
m=2,5 moli .102 g/moli=255 g Al2O3
MAl2O3=2.27 + 3.16=102----->102g/moli
12,046.10²³atomi de carbon------>g
1mol C-------12g----------6,023.10²³ atomi C
x g C----------12,046.10²³atomi C
x=12 . 12,046. 10²³ : 6,023. 10²³=24g C