Which is the limiting reactant

Question

Nitrogen gas and hydrogen gas are combined in a reaction to produce ammonia. If 6.0 moles of N₂ and 6.0 moles of H₂ are present in the mixture, which is the limiting reactant?

Show work

Answer 1

There are several ways to find the limiting reactant. One of the easiest is to simply divide the moles of each reactant by the corresponding coefficient in the balanced equation, and whichever value is less, that is the limiting reactant. In this problem we have ...

N₂ + 3H₂ ==> 2NH₃ ... balanced equation

For N₂ we have 6.0 mols N₂ ÷ 1 = 6.2

For H₂ we have 6.0 mols H₂ ÷ 3 = 2.0

Because 2.0 is less than 6.2 H₂ IS THE LIMITING REACTANT

Another way is to calculate the moles of product produced from each reactant:

6.0 mols N₂ x 2 mols NH₃ / 1 mol N₂ = 12 mols NH₃

6.0 mols H₂ x 2 mols NH₃ / 3 mols H₂ = 4 mols NH₃

This shows that H₂ is limiting