Which reactant to use to calculate yield? A chemist mixes 24.0 g $\ce{H2}$ with 8.0 g $\ce{N2}$. Assuming the reaction goes to completion, which reactant should she use to calculate the yield?


$$\ce{3H2 + N2 -&gt; 2NH3}$$
I believe it should be nitrogen. With 24 g of $\ce{H2}$, we have 11.9 mol of $\ce{H2}$. With 8 g of $\ce{N2}$, we have 0.3 mol of $\ce{N2}$. So, when I express the moles of $\ce{N2}$ in terms of $\ce{H2}$, I see that I only need 0.9 moles of $\ce{H2}$ – which means that $\ce{N2}$ is the limiting reacting and then used to calculate the theoretical yield, right?
You have the right thought process - you need to find which is the limiting reagent. 
Your calculation is correct, $N_2$ is limiting, so it can be used to calculate yield. Looks like we weren't really needed!