CuCO3
-se calculeaza masa molara
M=64 + 12 + 3.16=124--->124g/moli
124 g CuSO4--------------64g Cu---------12g C --------------48g O
100 g---------------------------x---------------------y---------------------z
x=100.64 : 124=51,61 % Cu
y=100.12 : 124=9,68%C
z=100.48 : 124=38,7% O %