A sample of pure carbon dioxide, irrespective of its source contains 27.27% carbon and 72.73% oxygen. The data support

Ratio of masses of “C” and “O” in CO2 = 27.27 : 72.73 ≈3:8Carbon dioxide obtained from any source consists of  C  and O  always combined in the ratio by mass of 12 : 32  (or) 3 : 8 (which is same as given percentages ratio)This illustrates the law of constant composition(That is  A sample of pure compound always contains same elements in same proportions by mass)