-calculez moli si masa Al pur care arde in 6 mol O2
4mol......3mol
4Al + 3O2-----> 2Al2O3
x.............6mol
x= 8mol Al
m= nxM= 8molx27gmol= 216g Al pur
-calculez masa de Al impur
p= m,px100/m,i
86= 216gx100/ m,i-------------------> calculeaza m,i !!!!