`1.80g` of a certain metal burnt in oxygen gave `3.0g` of its oxide `1.50g` of the same metal heated in steam gave `2.50g` of its oxide. Show that these illustrate the law of constant proportion .

Explanation

In the first sample of the oxide,
wt. of metal=1.80 g, wt. of oxygen =(3.0-1.80)g =1.2 g
`therefore ("wt. of metal")/("wt. of oxygen")=(1.80 g)/(1.2 g)=1.5`
In the second sample of the oxide,
wt of metal =1.50 g, wt. of oxygen=(2.50-1.50)g =1 g
`therefore ("wt. of metal")/("wt. of oxygen")=(1.50g)/(1 g)=1.5`
Thus, in both samples of the oxide the proportions of the weights of the metal and oxygen are fixed. Hence, the results follows the law of constant proportion.
Note : This law is not applicable in case of isotopes.