Combustion of Hydrocarbons (GCSE Chemistry)
Combustion of Hydrocarbons
Combustion of Hydrocarbons
- Combustion releases energy. When hydrocarbons are burnt in the presence of lots of oxygen, energy is released as a result of combustion. Carbon dioxide and water are also formed. The word equation is shown here:
hydrocarbon + oxygen ⟶ carbon dioxide + water (+ energy released)
- Hydrogen and carbon are oxidised. When a hydrocarbon is burnt in oxygen, the contents (hydrogen and carbon) are completely oxidised. During the reaction, the hydrogen and carbon atoms gain oxygen.
- Hydrocarbons are used as fuels. Due to the amount of energy released during a combustion reaction, hydrocarbons can be used as fuels. These include liquified petroleum gases, petrol and kerosene.
Practice Question: Write a balanced equation for the complete combustion of ethane (C2H6).
1. Write out the general equation. In this instance, we need the equation for complete combustion.
Hydrocarbon + oxygen ⟶ carbon dioxide + water
2. Fill in the formulae. Now that we have a general equation, we can rewrite it with the formula for ethane.
C2H6 + O2 ⟶ CO2 + H2O
3. Balance the equation. On the left-hand side we have 2 carbons, so we need 2 carbon dioxide molecules.
C2H6 + O2 ⟶ 2CO2 + H2O
On the left, we now have 6 hydrogen atoms. This needs 3 water molecules to balance.
C2H6 + O2 ⟶ 2CO2 + 3H2O
On the right-hand side, there are 7 oxygen atoms. We need to put 3.5 in front of the oxygen atoms on the left-hand side, but we don’t use decimals in equations, Therefore, we multiply everything by 2 to balance the equation.
2C2H6 + 7O2 ⟶ 4CO2 + 6H2O
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