Formula reactiei chimice: 2Cu+O2--->2CuO
la 2 moli cupru corespunde 1 mol oxigen, dar la 4 moli de cupru cati corespund? Raspuns 2 mol O2 (AM FOLOSIT REGULA DE TREI SIMPLA)
2 mol Cu.............1 mol O2
4 mol Cu.............x mol O2
x=(1×4)÷2=2 mol O2
