The chemical formula for octane is C8H18. A combustion reaction is one in which one reactant reacts with oxygen gas, O2. Since octane is a hydrocarbon, the products will be carbon dioxide and hydrogen. The balanced equation for the combustion of octane gas is:
2C8H18(g)+25O2(g)→16CO2(g)+18H2O(g)
Explanation:
First place an 8 in front of CO2 because of the 8 carbon atoms in a molecule of octane, and a 9 in front of H2O because of 18 H atoms divided by 2 atoms of O (in O2).
C8H18(g)+O2(g)→8CO2(g)+9H2O(g)
Balance the oxygen atoms on both sides of the equation. There are 25 O atoms on the right side of the equation. So we place a coefficient of 252 in front of the O2 molecule on the left.
C8H18(g)+252O2(g)→8CO2(g)+9H2O(g)
There cannot be a fraction as a coefficient, so we need to multiply the equation times 2.
2C8H18(g)+25O2(g)→16CO2(g)+18H2O(g)