[kciray]

We have this reaction
N₂ + 3H₂  2NH₃

We increased pressure and have more amount of NH₃. How can we pick out that compound, split it from mixture gas? It's practical question.

[Hunter2]

Ammonia is easily to get it as liquid by pressure and temperaur. So it can be separated. Nitrogen and Hydrogen boiling points more negative.

[Arkcon]

Ammonia has other properties useful as well.  For example, it reacts with water to form ammonium hydroxide, nitrogen and hydrogen aren't appreciably soluble in water.  Ammonia reacts with other reagents as well, which you can look up.  You can also look up the production of ammonia industrially, and you'll see the information Hunter2: provided.   I doubt you're going to put any producers out of business anytime soon -- pressurizing, and cooling and re-routing unreacted N2 and H2 back for more reactions is a chemical engineering feat, and very energy intensive.

[mikasaur]

The Haber Process!

Great example of equilibrium reactions, the effect of temperature on Gibbs energy, catalysts, engineering constraints, and the importance of chemistry in the modern world, and more...

As Arkcon said, you're not going to put people outta business anytime soon. People have been thinking about this for a while.