COMBUSTION REACTIONS
Combustion – a very rapid reaction of a substance with oxygen to
produce an oxide and release energy in the form of
heat and light.
 commonly referred to as burning
 easily identified by the production of heat (exothermic)
 type of synthesis reaction
FUEL + OXYGEN  OXIDE + ENERGY
Three requirements for a combustion reaction:
 Fuel
 Oxygen
Fire Triangle
 Heat
The most common fuels are hydrocarbons (molecules made up only
of hydrogen and carbon).
Complete Combustion
 When oxygen is available in sufficient amounts
 Characterized by a blue flame
Complete combustion of a hydrocarbon:
Hydrocarbon + Oxygen  Carbon dioxide + Water
There is enough oxygen present to combine with every carbon and
hydrogen atom present.
Incomplete Combustion
 If not enough oxygen is present, incomplete combustion occurs
 Characterized by an orange “dirty” flame
Incomplete combustion of a hydrocarbon:
Hydrocarbon + Oxygen  Carbon
Dioxide
+
Carbon + Carbon + Water
Monoxide
 An incomplete combustion reaction may produce any combination
of the carbon containing products, however it MUST include
water.
Incomplete combustion can be characterized by the presence of black
“soot” which indicates the presence of solid carbon.
Carbon monoxide is a clear, colourless gas which is highly poisonous.
Due to its similar size to diatomic oxygen, the hemoglobin in the
blood bind to the carbon monoxide depriving the brain of oxygen.
Examples:
 Complete combustion of pentane (C5H12)
C5H12 + 8 O2

5 CO2
+ 6 H2O
 Incomplete combustion of octane (C8H18)
C5H12 + 7 O2
C5H12 + 5 O2

Or

4 CO2
+
C + 6 H2O
4 CO + C + 6 H2O