Question

How many moles of hydrogen are needed to completely react with 2 moles of nitrogen

Answer 1

Assuming ammonia is the product of this reaction:

N2+3H2--->2NH3

2 mole N2 * (3 mol H2)/(1 mol N2)= 6 mol H2

You would need 6 mol of hydrogen gas to completely react with 2 mol of nitrogen.