N2 + 3H2 --> 2NH3
For nitrogen and hydrogen the initial moles is two, and none for ammonia.
At equilibrium there is 2X amount of moles of ammonia, how many moles of hydrogen and nitrogen are there at equilibrium?
I worked it out as there being 0 moles of hydrogen and one mole of nitrogen, although hydrogen would lose three moles you can't get negative quantities of moles.