Combustion is a chemical process involving burning of a substance in excess of air or oxygen. Energy is always released when a substance undergoes combustion process. Some familiar examples of combustion are:
- burning of coal, wood.
- burning of cooking gas, petrol, gasoline.
- burning of food in our body, etc.
Enthalpy of combustion. It is the enthalpy change accompanying the combustion of one mole of a substance in excess of oxygen or air.
It is denoted by Δ c H.
Since combustion reactions are always exothermic, enthalpy of combustion is always negative.