Răspuns:
4K + O2---> 2K2O
2Ca+O2---> 2CaO
2Zn+O2---> 2ZnO
A,Cu=64g/mol
miuCuO=80g/mol
2x64g.................2x80g
2Cu + O2---> 2CuO
12,8g..........................x
=x=m,teoretica=16gCuO
m,practica= 16x80/100g=...................................calculeza a!!!!!!
Explicație: