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?

Answer 1

First, write the balanced equation

N₂ + 3H₂ ==> 2 NH₃ …. Balanced equation

It takes 3 mols H₂ to react with 1 mol N_2. Since there are 6 moles of each, H₂ will be limiting.

An easy way to find the limiting reactant is to just divide the moles of each reactant by its coefficient in the balanced equation. Whichever value turns out less will be the limiting reactant. In the current example we have

6 mols N₂ ÷ 1 = 6

6 mols H₂ ÷ 3 = 2

2 is less than 6 so H₂ is limiting.