Question

Why do unsaturated carbon compounds produce sooty flame while saturated carbon compounds produce clean flame?

Answer 1

I think that my book is actually saying the percentage of carbon in unsaturated hydrocarbon is more than saturated hydrocarbon. Let's take the hydrocarbon with two carbon, which are saturated hydrocarbon(ethane), unsaturated hydrocarbons(ethene and ethyne).

The percentage of carbon in ethane(C2H6CX2HX6) =[2(12)/2(12) + 6(1)]⋅100[2(12)/2(12) + 6(1)]⋅100 = 80 %

The percentage of carbon in ethene(C2H4CX2HX4) =[2(12)/2(12) + 4(1)]*100[2(12)/2(12) + 4(1)]*100 = 86 %

The percentage of carbon in ethyne(C2H2CX2HX2) =[2(12)/2(12) + 2(1)]⋅100[2(12)/2(12) + 2(1)]⋅100 = 92 %

According from above, we can see unsaturated hydrocarbon have a higher percentage of carbon than saturated hydrocarbon. So, there is a sooty flame when burning unsaturated hydrocarbons and a clean flame when burning saturated hydrocarbon