Se aplica relatia : n= m : M ----------> in care n=nr. moli ; m=masa subst. ; M=masa molara
n=15g : 39g/moli=0,38 moli K
n=2g: 64g/moli=0,031 moli Cu
n=0,032 g : 32g/moli=0,001 moli oxigen
1mol oxigen --------2. 6,023 .10²³ atomi de oxigen
0,001 moli--------------x
x=0,001 . 2 . 6,023.10²³ atomi oxigen= 0,012046. 10²³ atomi oxigen
n=0,4 g : 4g/moli=0,1 moli He
1mol He---------6,023.10²³atomi He
0,1 moli-----------y
y=0,1 . 6,023.10²³atomi He =
