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Chemistry · Glossary

What is Complete and incomplete combustion?

Also known as: complete combustion · incomplete combustion

Definition 14.3 School Chemistry — Grades 1 to 12 · Chapter 14 — Combustion: Fuels, Products and Greenhouse Gases

A complete combustion takes place with enough oxygen: all the carbon of the fuel becomes carbon dioxide. An incomplete combustion takes place with too little oxygen: part of the carbon becomes carbon monoxide, CO\ce{CO}, or soot, which is carbon, C\ce{C}.

A Bunsen burner. Air let in at the bottom gives a blue flame and a complete combustion; without it the flame is yellow and smoky.
A Bunsen burner. Air let in at the bottom gives a blue flame and a complete combustion; without it the flame is yellow and smoky.
A cold spoon held in a yellow candle flame is blackened by soot: the combustion is incomplete.
A cold spoon held in a yellow candle flame is blackened by soot: the combustion is incomplete.

Examples

Example 14.4 (Methane short of oxygen)

With too little air, methane can burn to carbon monoxide or to soot:

2 CHX4+3 OX2→2 CO+4 HX2O,CHX4+OX2→C+2 HX2O.\ce{2CH4 + 3O2 -> 2CO + 4H2O}, \qquad \ce{CH4 + O2 -> C + 2H2O}.
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