On heating in the presence of air or dioxygen, alkanes are completely oxidized to carbon dioxide and water with the evolution of a large amount of heat. This is known as combustion reaction of alkanes.
General representative equation for combustion is:
CnH2n + 2 + \((\frac{3n+1}2)\) O2 \(\longrightarrow\) nCO2 + (n + 1) H2O + Heat
