Fertilisers

• Equation of Haber process

  N2 + 3H2 <-> 2NH3
• Haber process

  -> nitrogen (from air) and hydrogen (from natural gas) are pumped through pipes

  -> pressure of the mixture of gas is raised to 200 atmospheres (compressor)

  -> pressurised gases are heated to 450°C and passed through a tank containing iron catalyst beds

  ->reaction mixture is cooled so ammonia liquefies and can be removed

  ->unreacted nitrogen and hydrogen are recycled
• Fertilisers provide mineral ions needed for healthy growth in plants
• NPK fertilisers are formulations that contain nitrogen, phosphorus and potassium compounds to promote plant growth
• Sources of nitrogen in fertilisers

  ammonium ions (NH4)

  nitrate ions (NO3)
• Sources of phosphorus in fertilisers

  phosphate ions (PO4)
• Sources of potassium in fertilisers

  all common potassium compounds dissolve in water to produce potassium ions (K)

  ->potassium chloride

  ->potassium sulfate
• Ammonium nitrate


  NH4NO3
• Ammonium sulfate


  (NH4)2SO4
• Ammonium phosphate


  (NH4)3PO4
• Potassium nitrate

  KNO3
• Ammonia (NH3)

  ->alkali

  ->involved in neutralisation reactions

  ->produces ammonium ions
• Ammonia can be oxidised to produce nitric acid
• Ammonia + nitric acid -> ammonium nitrate

  NH3 + HNO3 -> NH4NO3
• Ammonium hydroxide + nitric acid -> ammonium nitrate + water


  NH4OH + HNO3 -> NH4NO3 + H2O
• Phosphate rock + Nitric acid —> calcium nitrate + phosphoric acid
• Ammonia + phosphoric acid —>ammonium phosphate
• Phosphate rock + sulfuric acid -> calcium sulfate + calcium phosphate (single superphosphate)
• Phosphate rock + phosphoric acid -> calcium phosphate (triple superphosphate)
• Ammonia + sulfuric acid -> ammonium sulfate
• Sulfuric acid is made from sulfur, air and water

  • sulfur + oxygen —>sulfur dioxide
  • sulfure dioxide + oxygen <—> sulfur trioxide
  • sulfur trioxide + water —>sulfuric acid
• Production of ammonia is exothermic