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

Apr 24, 2016

Incomplete combustion.

#### Explanation:

In circumstances where there is insufficient dioxygen gas, incomplete combustion of hydrocarbons to give $C O$ 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:

${C}_{6} {H}_{14} \left(l\right) + \frac{19}{2} {O}_{2} \left(g\right) \rightarrow 6 C {O}_{2} \left(g\right) + 7 {H}_{2} O \left(l\right)$

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

${C}_{6} {H}_{14} \left(l\right) + 9 {O}_{2} \left(g\right) \rightarrow 5 C {O}_{2} \left(g\right) + C O \left(g\right) + 7 {H}_{2} O \left(l\right)$ OR

${C}_{6} {H}_{14} \left(l\right) + 8 {O}_{2} \left(g\right) \rightarrow 4 C {O}_{2} \left(g\right) + C O \left(g\right) + C \left(s\right) + 7 {H}_{2} O \left(l\right)$

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.