0.200 mol of octane is allowed to react with 0.690 mol of oxygen, which is the limiting reactant? 2 C8H18 + 25 O2 ----> 16 CO2 + 18 H2O.
Well let us rebalance the equation to make our ideas of stoichiometric equivalence a bit more straightforward...
We combust octane, and we represent complete combustion in the usual way: balance the carbons as carbon dioxide; balance the hydrogens as water; and THEN balance the oxygens...
And here CLEARLY, given that dioxygen is specified to be in
For this PROPOSED stoichiometry...dioxygen is AGAIN the limiting reagent...
To conclude we HAVE NO HANDLE on the stoichiometry of this reaction....and the question is improperly proposed...
It should be oxygen.
We first look at the equation:
And so, we clearly see that
But since we only have