A,Al=27g/mol
A,Zn= 65g/mol
M,ZnO= (65gZn +16gO)/mol=81g/mol
2mol 3mol 3mol
2Al + 3ZnO----> Al2O3 + 3Zn
2x27g 3x81g -
24g 45g-------------> comparand datele, Al este in exces, asa ca masa Zn se calculeaza din masa ZnO
3X81g ZnO.............3X65gZn
45g............................x= 45x65/81 ......calculeaza !!!!