Petrol is a mixture of hydrocarbons.
Combustion of hydrocarbons is used to heat our homes because hydrocarbons are readily available, and energy is released in the reaction of hydrocarbons with oxygen.
We have seen that the product of reaction of carbon with oxygen depends on the amount of oxygen available.
The product of combustion of hydrocarbons also depends on the amount of oxygen available.
If there are only two oxygen atoms available as O2 for every methane molecule, combustion gives a mixture of soot (elemental carbon) and water.
CH4(g) + O2(g)
C(s) + 2H2O(g)Soot is one of the possible carbon-containing products of incomplete combustion of methane (or other hydrocarbons).
If there are three oxygen atoms available for every methane molecule, combustion gives a mixture of CO and water.
2CH4(g) + 3O2(g)
2CO(g) + 4H2O(g)CO is the other possible carbon-containing product of incomplete combustion of methane (or other hydrocarbons).
If there are four oxygen atoms for every methane molecule, complete combustion occurs, and a mixture of CO2 and water is formed.
CH4(g) + 2O2(g)
CO2(g) + 2H2O(g)Complete combustion of methane (or other hydrocarbons) gives CO2.
In practice incomplete combustion generally gives either CO or a mixture of CO and soot (elemental carbon).
The image shows (from left to right) the effect on the flame of a bunsen burner of increasing the amount of oxygen available to mix with the natural gas. In number 4 sufficient oxygen is available for complete combustion of the natural gas.
