The Haber Process

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  • Created by: Jo Wells
  • Created on: 20-04-13 13:07
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  • The Haber Process
    • nitrogen & hydrogen make ammonia
      • N2 + 3H2 <-> 2NH3 (+heat)
      • nitrogen obtained from air - 78% nitrogen
      • hydrogen from natural gas/other sources like crude oil
        • gases are first purified
          • nitrogen obtained from air - 78% nitrogen
      • some of the nitrogen reacts with the hydrogen to form ammonia - as reaction is reversible it goes both ways
        • the ammonia itself breaks down back into the nitrogen and hydrogen
    • industrial contitions
      • 200 atmospheres of pressure
      • 450 degrees C
      • iron catalyst
    • compromise
      • higher pressures favour the forward reaction (fewer molecules on the right side)
        • so pressure is set as high as possible to give the best % yield, without being too expensive
      • forward reaction is exothermic, so would work better with a lower temperature
        • but lower temperatures mean a lower rate of reaction - have to increase the temperature to get a faster rate
          • 450 degrees C is a compromise between maximum yield & speed of reaction
            • better to wait 20 secs for 10% than 60 secs for 20%
    • iron catalyst speeds up reaction & keeps costs down
      • makes reaction go faster - gets to equilibrium proportions faster, without affecting the position of equilibrium
      • without catalyst the temperature would need to be raised even higher to make reaction fast enough - reduce % yield even more


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