The Haber Process and NPK Fertilisers

• Haber process


  The process for the manufacture of ammonia
• Haber process


  • Uses nitrogen and hydrogen as raw materials
  • Passes the reactants over an iron catalyst at around 450 degrees Celsius and 200 atmospheres pressure
  • Produces ammonia, which is a reversible reaction
• Haber process


  1. Purify nitrogen and hydrogen

  2. Pass over iron catalyst at 450 degrees Celsius and 200 atmospheres

  3. Ammonia forms but some breaks down

  4. Cool ammonia to liquid and remove

  5. Recycle unreacted nitrogen and hydrogen
• Leshateliers principle


  If a system at equilibrium is subjected to a change in conditions, the system will shift to counteract the change and restore equilibrium
• Haber process forward reaction is exothermic


  Relatively cool temperature will shift equilibrium to the right to produce more ammonia
• Increasing temperature


  Increases rate of reaction but lowers yield of ammonia
• Increasing pressure


  Shifts equilibrium to the right to produce more ammonia
• 450 degrees Celsius and 200 atmospheres is a compromise temperature and pressure to balance rate and yield
• Iron catalyst increases the rate of the Haber process reaction but does not affect the position of equilibrium
• Graphs can be used to interpret the effect of reaction conditions on the yield of ammonia in the Haber process
• NPK fertilizers


  Fertilizers that contain compounds of nitrogen, phosphorus, and potassium
• NPK fertilizers


  • They improve agricultural productivity by helping plants grow larger and more rapidly
• Production of NPK fertilizers

  Variety of different raw materials are processed together to produce the exact fertilizer required
• Ammonium nitrate


  Main compound of nitrogen in NPK fertilizers, formula NH4NO3
• Production of ammonium nitrate


  Use ammonia produced by Haber process + nitric acid, react to form ammonium nitrate
• Potassium in NPK fertilizers

  Comes from potassium chloride or potassium sulfate, mined from the ground
• Production of phosphate compounds for NPK fertilizers

  Phosphate rock treated with nitric acid, sulfuric acid, or phosphoric acid to produce phosphoric acid, single superphosphate, or triple superphosphate
• Phosphoric acid produced from phosphate rock


  Cannot be added directly to plants, so it is neutralized with ammonia to produce ammonium phosphate
• You will find plenty of questions on fertilizers in the revision workbook