1.80 g of a certain metal burnt in oxygen gave 3.0 g of its oxide. 1.50 g of the same metal heated in steam gave 2.50 g of its oxide. Show that these results 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.