haber process

• the haber process is used to manufacture ammonia

  this can be used to produce nitrogen-based fertilisers
• the raw materials for the haber process:

  • nitrogen from AIR
  • hydrogen from NATURAL GAS (methane)
• word equation:

  • nitrogen + hydrogen <--> ammonia

  symbol equation:

  • N2 (g) + 3H2 (g) <--> 2NH3 (g)
• the reaction is:

  • reversible
  • production of ammonia (forwards) is exothermic
  • has a 100% atom economy as there is only 1 product
• conditions:

  • IRON CATALYST
  • 200 ATM PRESSURE
  • 400-450 TEMP
• what happens?

  • nitrogen and hydrogen molecules react to form ammonia
  • some of the ammonia breaks back down into nitrogen and hydrogen as it is a reversible reaction
  • ammonia is cooled down and liquefies and is removed, with the remaining hydrogen and nitrogen being recyled
• • temp of 400-450 is used : compromise temp, relatively fast rate and relatively high yield of ammonia
  • this is because the backwards reaction is endothermic so by increasing the temperature, the position of equilibrium shifts to the right which decreases the yield of ammonia
  • however, increases the temperature increases the rate or reaction as the particles move faster therefore have an increased frequency of successful collisions
• • iron catalyst increases the rate of reaction
  • it has no effect on the position of equilibrium
• • 200 atm pressure is used
  • there a fewer molecules of gas on the right hand side
  • so increasing the pressure shifts the position of the equilibrium to the right
  • this increases the yield of ammonia
  • higher pressures also increase there cost as equipment that can withstand a higher pressure must be used
• • highest % of ammonia at a low temp
  • but this decreases the rate
  • so increasing temp increases rate but decreases yield
  • a higher temp requires more energy