Question

Why does an unsaturated hydrocarbon leaves a sooty flame on burning?

Answer 1

Formation of sooty particles is due to two reasons:

• A larger amount of carbon being left out without getting oxidized as in the case of unsaturated hydrocarbons, where the amount of carbon is more compared to alkanes.
• A large supply of oxygen is required in order to heat and break the double bond, this means that in a given supply of oxygen, unsaturated hydrocarbons use most of the oxygen in order to break the bonds and therefore the remaining left out oxygen is not sufficient enough to burn the carbon content left (which is quite high) so it results in formation of sooty hydrocarbons which is nothing but residue of the carbon which was partially burnt.