Răspuns:
nr moli= masa/Masa moleculara
nr atomi= nr moli*6.022*10²³
masa=nr moli*Masa moleculara
a)Masa moleculara O2=2*16=32g/mol
64 g O2=64/32=2 moli O2=2*6.022*10²³ =12.044*10²³ atomi O2
b)Masa molecula Mg=24g/mol
18.066*10²³ atomi Mg=(18.066*10²³)/(6.022*10²³)=3 moli Mg =3*23=69g Mg
