Question

How many moles of `O_2` are required to generate 18 moles of `H_2O` in the reaction `2C_8H_18 + 25O_2 -> 16CO_2 + 18H_2O`?

Answer 1

You will need 25 moles, but this is not based on the equation alone.

Explanation:

`18mol H_2 O x ((25 molO_2)/ (18molH_2 O)) = 25 mol O_2`

Moles of water cancel, leaving you with moles of Oxygen.
Factor out 18/18=1.
25 x 1 = 25