A chemical equation is said to be balanced chemical equation if it has equal number of all the constituent atoms on both side of the reaction arrow.
The balanced chemical reaction for combustion of pentane is as follows:
![C_(5)H_(12) + 8O_(2)\rightarrow 5CO_(2) + 6H_(2)O](https://img.qammunity.org/2019/formulas/chemistry/middle-school/bc9j0p2677nbq6924ph6oujv37k1crp5eq.png)
From the above balanced chemical equation it is clear that 1 mol of
reacts with 8 moles of
to form 5 mole of
.
Therefore, the mole ratio of oxygen to pentane is 8:1 here.