se foloseste relatia :
n= m : M [ n=nr.moli ; m=masa subst. ; M=masa molara ]
n=90g : 18g/moli=5 moli H2O
n= 320g : 80g/moli=4 moli SO3
n=63g : 63g/moli=1mol HNO3
n=500g : 100g/moli=5 moli CaCO3
calculeaza masele molare singur ,dupa model !!!!
MH20=2 + 16=18------> 18g/moli
MSO3=32 + 3.16=80------>