Question

How do you determine limiting reagant and excess reagant?

Answer 1

The way I do it is take the amounts of reactants you have and find the amounts of a product (if there is more than one product just pick one).

Answer 2

The reactant that makes the smallest amount of that product is limiting. i.e. It runs out first.

Answer 3

The other one(s) is/are excess.

Answer 4

You can also "normalize" the amounts of moles of the reactants (statistically speaking) to compare them. Do this by dividing the moles of each reactant by it's stoichiometric coefficient.

for example if you had 2A + 3 B -> C

and you had 4 moles of A and 4 moles of B

\(normalized~moles~of~A=\dfrac{4~moles}{2}=2~moles\)

\(normalized~moles~of~B=\dfrac{4~moles}{3}=1.5~moles\)

the one with less moles (in this case B) is the limiting reactant.

Answer 5

Thanks!