Question

unsaturated hydrocarbon gives a yellow flame with lots of black smoke when burnt in oxygen. give reason

Answer 1

Unsaturated hydrocarbons like ethyne produce a yellow flame when burnt in oxygen due to incomplete combustion in air.The percentage of carbon is comparatively higher than that of alkanes and so does not get completely oxidized in air.

Answer 2

Answer:

when saturated compounds are burnt in air,they give a clear(blue) flame but the burning of unsaturated compounds(alkenes and alkynes) gives a sooty (yellowish) flame.