# How would you write a balanced equation for the combustion of octane, C8H18 with oxygen to obtain carbon dioxide and water?

Nov 10, 2015

$2 {C}_{8} {H}_{18} + 25 {O}_{2} \to 16 C {O}_{2} + 18 {H}_{2} O$

#### Explanation:

You just have to check the number of atoms of each element is the same in both sides.
You can do it by steps starting with the unbalanced equation

${C}_{8} {H}_{18} + {O}_{2} \to C {O}_{2} + {H}_{2} O$

By making a list of the elements and the number of atoms on each side of the equation

$8 - C - 1$
$18 - H - 2$
$2 - O - 3$

Then as you can see, the molecule with 1 carbon ($C {O}_{2}$) you have to multiply by eight, the molecule with 2 hydrogens (${H}_{2} O$) you have to multiply it by 9 to be equal to the left. And when you find that you have to multiply by a fraction then you can multiply the whole equation by an integer so you have only integers.