When Aluminum oxide is heated with iron no reaction takes place?

Explanation:

That's correct. Once Aluminum becomes an ion, it is very hard to force it to take back its electrons. Only a few elements can do it. Iron is not one of them.

the reaction mixture contains some ammonia, plus a lot of unreacted nitrogen and hydrogen. the mixture is cooled and compressed, causing the ammonia gas to condense into a liquid. the liquefied ammonia is separated and removed. the unreacted nitrogen and hydrogen are then recycled back into the reactor .