What is the limiting reagent when #12.5*lb# pentane are reacted with a #12.5*lb# mass of dioxygen gas?
We need (i) a stoichiometric equation:
And (ii) we need equivalent quantities of dioxygen and pentane. We know that
Clearly, there is INSUFFICIENT dioxygen gas for complete combustion. And thus
By the way the question proposed that oxygen and pentane were mixed together.........this is not something that I would be happy doing, and I would run a long way away if I saw someone doing this....
The limiting reactant is oxygen.
Here's another way to identify the limiting reactant.
We know that we will need a balanced equation with masses, moles, and molar masses of the compounds involved.
1. Gather all the information in one place with molar masses above the formulas and everything else below the formulas.
Note: We do not have to stick with gram-moles. We can use pound-moles because the numbers will still be in the same ratio.
2. Identify the limiting reactant
An easy way to identify the limiting reactant is to calculate the "moles of reaction" each will give:
You divide the moles of each reactant by its corresponding coefficient in the balanced equation.
I did that for you in the table above.