The Haber Process

Nitrogen and Hydrogen are needed to make Ammonia

- Temperature- Pressure

N     +     3H         2NH     (+ heat)  

- Higher pressure favours the forward reaction- So the pressure is set as high as possible to give the best % yield without it being too expensive- Forward reaction is exothermic - inc the temp will move the equilibrium away from ammonia, the yield of ammonia is greater at lower temperatures- BUT, lower temperatures have a lower rate of reaction so they keep it high- 450°C  is a compromise between maximum yield and speed of reaction  (better to wait 20 seconds for 10% yield than 60 seconds for 20% yield)- Ammonia is formed as a gas but as it cools in the condenser it is liquefied and is removed- Unused hydrogen and nitrogen are recycled so nothing is wasted

- The iron catalyst speeds up the reaction so it gets to equilibrium proportions quicker- Without it the temp would have to be raised further which would reduce the % yield

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