In the combustion of hydrocarbon, carbon monoxide is formed. What has occurred?

1 Answer
Apr 24, 2016

Incomplete combustion.


In circumstances where there is insufficient dioxygen gas, incomplete combustion of hydrocarbons to give #CO# gas and #C# as soot can occur. This typically occurs in internal combustion engines and (more so) in diesel engines.

Complete combustion of hexanes may be represented by an equation:

#C_6H_14(l) + 19/2O_2(g) rarr 6CO_2(g) + 7H_2O(l)#

If some of the hexanes were incompletely combusted I could write:

#C_6H_14(l) + 9O_2(g) rarr 5CO_2(g) + CO(g) + 7H_2O(l)# OR

#C_6H_14(l) + 8O_2(g) rarr 4CO_2(g) + CO(g) + C(s) + 7H_2O(l)#

Longer chain hydrocarbons (such as diesels) typically burn dirty. How do I know that 1 mole of soot or carbon monoxide were produced in the given equations? Of course, I don't know that, but I know there were SOME products of incomplete combustion, and I modified the complete combustion to represent this. A typical internal combustion engine (or a furnace or a diesel engine) is designed to permit some incomplete combustion.