Combustion of alkanes

Reactions of saturated hydrocarbons either result in destruction of the carbon skeleton (combustion below) or give rise to multiple products as seen in the reaction with the halogen Cl2.

Combustion is the term referring to reaction with oxygen.
Combustion of alkanes is a very important reaction because it is used in
 
heating and power generation

CH4(g) + O2(g)    CO2(g) + H2O(g)
running of automobiles

C7H16(g) + 11O2(g)    7CO2(g) + 8H2O(g)

In combustion reactions of hydrocarbons all C-C and C-H bonds are replaced by C-O and O-H bonds.
 
The number of moles of CO2 generated equals the number of carbon atoms in the hydrocarbon.
The number of moles of H2O generated equals half of the number of hydrogen atoms in the hydrocarbon.