First, we have to write a balanced equation for the production of ammonia (NH₃) from hydrogen gas (H₂) and nitrogen gas (N₂):
N₂ + 3H₂ → 2NH₃
Now, the mole ratio of H₂ : NH₃ is 3 : 2 based on the coefficients of the balanced equation.
If the moles of H₂ = 15 moles
then the moles of NH₃ produced = (15 mol ÷ 3) × 2
= 10 mol
Thus, the number of moles of NH₃ produced when 15 mol of hydrogen gas is combined with excess nitrogen gas is 10 mol.