Combustion Reactions
• Element or compound reacts
with oxygen, releasing energy
(heat, light)
• O2 always a reactant
• Hydrocarbon often other reactant
• Products = CO2 and H2O
(when reactant = hydrocarbon)
Hydrocarbons
Alkanes (CnH2n + 2)
Methane
Hexane
Ethane
Heptane
Propane
Octane
Butane
Nonane
Pentane
Decane
COMPLETE combustion of a
hydrocarbon…
 CO2 + H2O + energy/heat
What happens if O2 is limited?
Combustion of heptane
C7H16 + O2 
CO2 + H2O
Combustion of glucose
C6H12O6 + O2  CO2 + H2O
Combustion of ethanol
C2H5OH
Some combustion reactions are
also combination reactions.
2Mg + O2 
2MgO
S + O2  SO2