Carbon and oxygen combine to form two oxides, carbon monoxide and carbon dioxide in which the ratio of the weights of carbon and oxygen is respectively 12:16 and 12:32 These figures illustrate the

In $\mathrm{CO}$, molar mass of $\mathrm{C}$ is 12 and molar mass of O is 16.

And in case of CO₂, molar mass of C is 12 and for O it is 32.

Keeping carbon as the fixed mass, the ratio of oxygen is 1:2 (simple whole number ratio).

Thus justifying the law of multiple proportion.

As, law of multiple proportion states that, when two elements combine to form more than one compound, then the masses of one of the elements which combine with a fixed mass of the other element are in a simple whole number ratio.