se stie ca 1 mol substanta contne acelasi numar de particule, numit numarul lui Avogadr0
calculez moli O2: n= m/M= 64g/32g/mol= 2molO2--> 4molO-
4mol O contin 4N,A atomi
4molN-----> m=nxM= 4molx14g/mol atomi= 56g N
4molC-----> m =4molx12g/mol atomi= 48gC
4mol Na-----> m= 4molx23g/mol atom= 92g Na