The Haber Process

• react nitrogen with hydrogen, yields ammonia
• ammonia used to make nitrogen-based fertilisers, which farmers can add back to the soil.
• Haber Process steps:

  • collect and purify nitrogen and hydrogen gases
  • pass over an iron catalyst at 450 degrees celsius and pressure of 200 atmospheres. results in ammonia gas
  • the reaction is reversible, so not all of the ammonia stays as ammonia. some will break down to give the reactants, nitrogen and hydrogen.
  • ammonia gas cools in a condenser. ammonia is removed from condenser once it is a liquid
  • we can recycle any unused hydrogen and nitrogen back into the process to create more ammonia. waste of valuable products can be avoided
• Haber Process conditions:

  • 450 degrees celsius - temperature
  • 200 atmospheres - pressure
  • Iron catalyst used

  Lower temperature = produce more ammonia

  Increase pressure = make more ammonia

  A compromise temperature taking yield and rate into account must be found.

  An economically viable medium pressure of 200 atmospheres is used.
• High pressure cons:

  • needs thicker pipes
  • safety risk?
  • more expensive
• The forward reaction is exothermic. An increase in temperature moves the equilibrium in the endothermic direction, in this case, decreasing the yield of ammonia.

  A compromise temperature that takes rate and yield into account must be found - 450 degrees celsius