What is the difference between a complete and incomplete combustion reaction?

1 Answer
Nov 7, 2015

Typically complete and incomplete combustion relates to the combustion of hydrocarbons. Here, complete combustion indicates that carbon dioxide is the sole oxidation product; incomplete combustion means otherwise.


We can take octane as our exemplar:

#C_8H_18(g) + 25/2O_2(g) rarr 8CO_2(g) + 9H_2O(g)#

Is the above equation balanced? Don't trust my arithmetic! Here, all the hydrocarbon reactant ends up as carbon dioxide product; the carbon in the hydrocarbon is completely combusted to #CO_2#. Under the conditions of a ICE or diesel fuel engine, combustion would be incomplete, and some products of incomplete combustion, #CO#, or particulate #C#, would result. I can represent this by the following reaction:

#C_8H_18(g) + 11O_2(g)rarr 6CO_2(g) + CO(g) + C(s) + 9H_2O(g)#

Again, is this balanced? Why or why not? Of course the products would have to be analyzed in order to see the effectiveness of combustion; this is simply a representation.