Question

Carbon form two oxides, the first contains 42.9% C and the second contains 27.3% carbon. Show that these are in agreement with the law of multiple proportions.

Answer 1

In the first compound: 

C = 42.9% 

O = 100-42.9 = 57.1% 

So, the ratio between the masses of C and 

O = 42.9:57.1 = 1:1.33 

In the second compound: 

C = 27.3% 

O= 100-27.3= 72.7% 

So, the ratio between the masses of C and 

O = 27.3 : 72.7= 1:2.66 

Hence, the ratio of masses of oxygen which combines with a fixed mass of carbon is 1.33:2.66 or 1:2, a simple whole number ratio. 

This illustrates the law of multiple proportions.