Another important type of reaction, in addition to the four types above, is that of the combustion of a hydrocarbon. When a hydrocarbon is burned with sufficient oxygen supply, the products are always carbon dioxide and water vapor. If the supply of oxygen is low or restricted, then carbon monoxide will be produced. This is why it is so dangerous to have an automobile engine running inside a closed garage or to use a charcoal grill indoors.

• Hydrocarbon (C_xH_y)  +  O_2(g)  -->    CO_2(g)  +  H₂O_(g)

• Ex. CH_4(g)  +  2O_2(g)  -->    CO_2(g)  +  2H₂O_(g)

• Ex. 2C₄H_10(g)  +  13O_2(g)  -->    8CO_2(g)  +  10H₂O_(g)

NOTE:

• Complete combustion means the higher oxidation number is attained.
• Incomplete combustion means the lower oxidation number is attained.
• The phrase "To burn" is another way to Express combustion reactions. This typically means you need three parts: fuel, oxygen and heat