How many moles of nh3 can be produced from 15.0 mol of h2 and excess n2?

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.