Question

in the production of ammonia, N2 + 3H2 --> 2NH3, if you start with 3 mol of N2 and 6 mol of H2, identify the limiting reagent and the excess reagent.

Answer 1

From the equation, 1 mole of N2 needs 3 moles of H2 for complete reaction.
Now, you have 3 moles of N2, how many moles of H2 do you need for the complete reaction?

Let the no. of moles of H2 you need for complete reaction you found be x.
i) if x<6, H2 is the excessing reagent
ii) if x>6, H2 is the limiting reagent