The balanced chemical equation tells you the stoichiometry of the reaction, meaning the ratio of moles of each reactant and product.

In this reaction:

* 2 moles of octane (C8H18) react with 25 moles of oxygen (O2)

* This produces 16 moles of carbon dioxide (CO2) and 18 moles of water (H2O).

Therefore, 18 moles of water are produced in this reaction.