One volume of a gaseous compound containing carbon, hydrogen, and oxygen was burnt in the presence of 2 volumes of oxygen. The resultant gases contained 2 volumes of carbon dixoide and 2 volumes of steam. Find the molecular formula of the compound, if all the volume were measured under the same conditions of temperature and pressure.

Explanation

Let the formula of the compound be `C_(x) H_(y) O_(2)`.
Combustion may be represented as under.
`underset(1 "vol")(C_(x) H_(y) O_(z)) + underset(2 "vol")("Oxygen") rarr underset(2 "vol")("Carbon dioxide") + underset(2 "vol")("Stream")`
By Avogadro's hypothesis:
`{:(1 "mol", 2 "mol", 2 "mol", 2 "mol"), ( , "or 4 atom", "or 2 atom C", "or 4 atom C"), (, , "and 4 atoms O", "and 2 atoms O"):}`
Now, 2 molecules of `CO_(2)` contains 2 atoms of carbon and these must have come from the compound. Hence, value of `x = 2`. Again, 2 molecules of steam contains 4 atoms of hydrogen and they, too, have come from the compound. Hence, the value of `y = 4`.
By the comparsion of oxygen atoms on both sides of the above equation, the value of `z` works out to be 2.
Hence, the molecular formula of the compound is `C_(2) H_(4) O_(2)`.