A reversible reaction between Nitrogen N2 and Hydrogen 3H2 = Ammonia 2NH3 and heat
Nitrogen extracted from air (78% nitrogen, 21% oxygen). Hydrogen obtained from natural gas. Because its reversible, not all the products will convert - dynamic equilibrium.
Industrial manufacture of ammonia uses high pressures (of 200 atmospheres) as it favours the forward reaction of ammonia. Highest pressure to give best % yield.
The forward reaction is exothermic so incr. temp moves the equilibrium the wrong way so the yield is slightly less. However, high temps increase rate of reaction. Compromise - 450C.
Ammonia is formed as gas but it cools in condensor, liquefies and is removed.
The iron catalyst used increase reaction rate but doesnt affect % yield.
Nirtogenous fertilisers, made from ammonia, increase plant growth. But if they enter rivers/lakes they can cause eutrophication - excessive growth of algae layer on surface. Plants living below th surface die as they can no longer photosynthesis - algae blocks light. Decomposers then feed on dead plants, use up all the oxygen in water, so fish die. - Farmers should be careful not to apply excess fertiliser.
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