Question

How can a mixture of ammonia and hydrogen be seperated?

Answer 1

A jug of ammonia (Not hard to keep liquid at room temperature with modest pressure.) has more hydrogen in it than a jug of pure liquid hydrogen!* (which is very hard to keep liquid even with huge pressures and very cold temperatures)

Answer 2

The ammonia molecules have weaker inter molecular bonds then the hydrogen and nitrogen, this means that the ammonia condensed at a lower temperature so will be a liquid that will be separated from the reaction, while the nitrogen and hydrogen remain as gases so are easy are recycle back into the reacting chamber.