NPK

• fertilisers replace missing elements in the soil to help plants grow bigger and faster , increasing the yield
• NPK contains compounds of:

  • nitrogen
  • phosphorus
  • Potassium

  which improve agricultural productivity
• Industrial production of NPK fertilisers can be achieved using a variety of raw materials which are processed together to produce the fertiliser
• NPK fertilisers are formulations of various salts

  containing appropriate percentages of the elements
• main compound = ammonium nitrate

  this is made by using ammonia which is used to manufacture ammonium salts and nitric acid (Haber process)
• potassium comes from salts of:

  • potassium chloride
  • potassium sulfate

  these are both mined from the ground and can be used directly (they are soluble so can be absorbed by the roots of plants)

  • phosphate rock

  cannot be used directly as it is insoluble
• • phosphate rock + nitric acid --> phosphoric acid + calcium nitrate
  • phosphate rock + sulfuric acid --> calcium sulfate + calcium phosphate (A SINGLE SUPERPHOSPHATE)
  • phosphate rock + phosphoric acid --> calcium phosphate (TRIPLE SUPERPHOSPHATE)
• a double superphosphate is a mixture of single and triple superphosphates
• ammonium nitrate - NH4NO3

  ammonium - NH3

  nitric acid - HNO3
• ammonium nitrate is produced by reacting ammonia with nitric acid - neutralisation reaction
• school lab:

  • dilute solutions of ammonia and nitric acid = safe
  • produce crystals with water bath and bunsen burner, requires a lot of heat energy
  • small amount of ammonium nitrate in one go (batch process)

  industry:

  • ammonia is used as a gas and nitric acid is concentrated.
  • dangerous and exothermic
  • heat must be safely removed and is used in later stages (eg energy for evaporation)
  • continuous process