How to find the limiting reactant given moles?
1 Answer
If you're given the moles present of each reactant, and asked to find the limiting reactant of a certain reaction, then the simplest way to find which is limiting is to divide each value by that substance's respective coefficient in the (balanced) chemical equation; whichever value is smallest is the limiting reactant.
As an example, let's say we have the reaction
and that we're given
-
3 moles of hydrogen -
2 moles of oxygen
The limiting reactant is that whose value is smallest after dividing the mole number by their coefficient:
We see that the number for hydrogen is the lower value, so hydrogen is the limiting reagent.
Notice also how the limiting reactant isn't necessarily the reactant present in a larger quantity; there were
3 "mol H"_2 and2 "mol O"_2 , but hydrogen was limiting.