A combustion reaction is a major class of chemical reactions. Combustion usually occurs when a hydrocarbon reacts with oxygen to produce carbon dioxide and water.
The balanced equation of combustion of octane is:
2 C₈H₁₈ + 25 O₂ → 16 CO₂ + 18 H₂O.
1.0 mole of octane is combusted completely with 25.0 mole of O₂ to produce 16.0 mole of CO₂ and 18.0 mole of H₂O.