Chapter 10 Ammonia

• Ammonia


  • used to manufacture of fertilisers
  • the Haber process is used to manufacture ammonia
• Haber Process

  • used to manufacture ammonia
  • Reaction between nitrogen and hydrogen is a reversible reaction
  • N2 +3H2 <-> 2NH3
  • temperature : 400 degree celcius
  • pressure : 250 atm
  • catalyst : finely divided iron catalyst
  • increasing pressure increases yield of ammonia and rate of reaction, but it is expensive to build containers and pipes that can withstand the pressure
  • increasing temperature increases the rate of reaction but reduces the yield
  • catalyst speeds up rate of reaction
• Haber Process Steps

  1. nitrogen is obtained from air and hydrogen is obtained from the cracking of crude oil
  2. in the main reactor, gases are passed over finely divided iron catalyst. Temperature is 400 degree celcius and pressure is 250 atm
  3. In the cooling chamber, gases are cooled and ammonia changes from gaseous state to liquid state. Liquid ammonia is produced
  4. unreacted nitrogen and hydrogen are recycled and passed through the reactor again
• Reversible Reactions

  • precipitation is an irreversible reaction
  • in reversible reactions, the reaction goes forward and backward at the same time. So the yield of the product is not 100%
• Conditions to Consider in Industrial Manufacturing Processes


  • rate of reaction
  • yield of product
  • cost
  • safety
• Increasing Rate of Reaction

  • Increasing temperature
  • Increasing concentration
  • Increasing pressure if gases are involved
  • Using a catalyst
• Factors Affecting Yield

  • temperature
  • concentration
  • pressure if gases are involved