3moli H3PO4
m g
-se calculeaza masa molara a H3PO4
MH3PO4= 3+ 31 + 4.16=98-------->98g/moli
- se aplica relatia :
n = m : M ------> in care n=nr.moli ; m=masa subst. ( g ) ;
M=masa molara ( g/moli )
-problema cere masa acidului fosforic
m= n . M
m=3moli . 98g/moli=294 g H3PO4