Methane contains 75 % carbon and 25% hydrogen, by mass. Carbon dioxide contains 27.27 % carbon and 72.73% oxygen, by mass. Water contains 11.11 % hydrogen and 88.89% oxygen, by mass. Show that the data illustrates the law of reciprocal proportion.

Explanation

Methane and carbon dioxide, both contains carbon and hence, carbon may be considered as the third element. Now, let the fixed mass of carbon = 1 gm. Then,
the mass of hydrogen combined with 1 gm carbon in methane
`" "=25/75=1/3gm`
and the mass of oxygen combined with 1 gm carbon in carbon dioxide
`" "=72.73/27.27=8/3gm`
Hence, the mass ratio of hydrogen and oxygen combined with the fixed mass of carbon, `r_(1)=1/3:8/3=1/8` Now, the mass ratio of hydrogen and oxygen in water,
`" "r_(2)=11.11/88.89=1/8`
As `r_(1)" and "r_(2)` are same , the data is according to the law of reciprocal proportion.