Răspuns:
1000kfg...........10kg
688,88kg........xkg
x=688,88×10/100=68,888kg fosfor pur
MP=31kg/kmol
MO2 =2×16=32kg/kmol
MP2O5 =2×31+5×16=142kg/kmol
4×31kg......5×32kg......2×142kg
4P + 5 O2=> 2P2O5
68,888kg.....xkg.......... ykg
x=68,888×5×32/ 4×31=calculează
y=68,888×2×142/4×31= calculează