Combustion
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Combustion or burning is an exothermic reaction between a substance (the fuel) and a gas (the oxidizer) to release heat. Combustion normally occurs in oxygen (often in the form of gaseous O2) to form oxides. However, combustion can also take place in other gases like chlorine.
There are also 2 types of combustion: complete and incomplete.
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Rapid combustion
Rapid combustion is a form of combustion in which large amounts of heat and light energy are released. This is used in forms of machinery, such as internal combustion engines, and in fuel-air explosives and spud guns.
Slow combustion
Slow combustion is a form of combustion which takes place at low temperatures. Respiration is slow combustion.
Complete Combustion
In complete combustion, the reactant will burn in oxygen, producing a limited amount of products. When a hydrocarbon burns in oxygen, the reaction will only yield carbon dioxide and water. When elements such as carbon, nitrogen, sulfur, and iron are burned, they will yield the most common oxides. Carbon will yield carbon dioxide. Nitrogen will yield nitrogen dioxide. Sulfur will yield sulfur dioxide. Iron will yield iron (III) oxide (iron (III) is the more common oxidation state). Complete combustion is generally impossible to achieve unless the reaction occurs in a lab environment where all the conditions are being controlled.
Incomplete Combustion
In incomplete combustion, where sufficient oxygen for complete combustion is lacking, the reactant will burn in oxygen, but will produce numerous products. When a hydrocarbon burns in oxygen, the reaction will yield carbon dioxide, water, carbon monoxide, and various other compounds such as nitrogen oxides. Incomplete combustion is much more common and will produce large amounts of byproducts, and in the case of burning fuel in automobiles, these byproducts can be quite lethal and damaging to the environment.
Chemical equation
Generally, the chemical equation for combusting a hydrocarbon in oxygen (such as octane) is as follows:
- CxHy + (x + y/4)O2 → xCO2 + (y/2)H2O
For example, the burning of propane is:
- C3H8 + 5O2 → 3CO2 + 4H2O
Word Equation
Simplified, the simple word equation for the reaction of combustion is Fuel + Oxygen -> Heat + Water + Carbon dioxide.
See also
- Heat of combustion
- spontaneous combustion
- fire
- deflagration
- detonation
- pyrolysis
- phlogiston
- pyrophoric
- internal combustion engine
- external combustion engine
- rotary combustion engine
- Staged combustion cycle (rocket)
- measurement techniques
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