4P+5O2=>2P2O5
nP=$\frac{6,2}{31}$ =0,2(mol); nO2=$\frac{6,72}{22,4}$ =0,3(mol)
Theo PTHH, ta có: $\frac{0,2}{4}$ <$\frac{0,3}{5}$ =>O2 dư
nO2(dư)=0,3−$\frac{0,2.5}{4}$ =0,05(mol)
mO2(dư)=0,05.32=1,6(g)
nP2O5=$\frac{2}{4}$ .nP=$\frac{2}{4}$ .0,2=0,1(mol)
mP2O5=0,1.142=14,2(g)