or

Phosphorous and oxygen combined to each other to give PO and PO. Which law of stoichiometry is illustrated. Also state the law.

Here,
In P2O3, 62gm of Phosphorous combined with 48gm of oxygen.
In P2O5, 62gm of Phosphorous combined with 80gm of oxygen.

⇒Ratio of mass of oxygen in P2O3 and P2O5 = 48:80 = 3:5 which is simple whole number ratio.

In this reaction, the ratio of mass of oxygen in PO and PO combined with fixed mass of phosphorous bear simple whole number ratio.

This illustrates, the law of multiple proportion of stoichiometry which states that, "When two elements combined to each other to give two or more products then the ratio of mass of one element in this compounds which combine with fixed mass (same mass) of another element bear simple whole number ratio."