You're asking about the reaction of hydrogen and nitrogen to form ammonia:

N₂ + 3H₂ → 2NH₃

Here's how to figure out the moles of nitrogen needed to react with 3 moles of hydrogen:

1. Mole Ratio:

* The balanced equation shows a 1:3 mole ratio between nitrogen (N₂) and hydrogen (H₂). This means for every 1 mole of nitrogen, you need 3 moles of hydrogen.

2. Calculation:

* Since you have 3 moles of hydrogen, you need 1/3 the amount of nitrogen:

* Moles of nitrogen = (3 moles H₂) / (3 moles H₂ / 1 mole N₂) = 1 mole N₂

Answer: You need 1 mole of nitrogen to react completely with 3 moles of hydrogen.