"How many moles of oxygen are required to react completely with 5 mol C(8)H(18)?"

2C(8)H(18) + 25O(2) => 16CO(2) + 18 H(2)O

In the question, how do I know if "oxygen" means the molecule O(2) or the element O?

3 answers

http://www.jiskha.com/display.cgi?id=1285089963 as an example.

Oxygen refers to the diatomic molecule, O2.
But if the question wanted me to find the moles of O, how would it be phrased? Thanks
It would ask, moles of the oxygen free atom, O.