Haber Process

• Haber Process is used to make Ammonia from Hydrogen and Nitrogen.

  N2 + 3H2 -><- 2NH3

  Nitrogen + Hydrogen -><- Ammonia

  It is a reversible reaction
• The nitrogen is easily obtained from the air.

  The hydrogen comes from reacting methane with steam to form hydrogen and carbon dioxide.
• The reactant gases are passed over an iron catalyst at a high temperature of 450 degrees with a high pressure of 200 atmospheres.
• The reaction is reversible, so some of the ammonia produced converts back into hydrogen and nitrogen again, it reaches a dynamic equilibrium.
• The Ammonia is initially formed as a gas but condenses in the condenser to form liquid ammonia.

  The Nitrogen and Hydrogen are recycled so nothing is wasted.

  The Ammonia produced can then be used to make ammonium nitrate which is a very strong fertiliser.
• The reaction is reversible so a compromise must be made.

  Conditions such as the temperature can affect the rate of reaction.

  The conditions of the Haber process affect yield.

  Increasing pressure, increases yield.

  Increasing temperature, increases the rate of reaction.

  The equilibrium lies further to the right at a higher pressure.
• The forward reaction is exothermic so an increase in temperature will move the equilibrium to the left, away from ammonia.

  Lower temperatures mean a slower rate of reaction.

  450 degrees is a compromise between maximum yield and rate of reaction.
• Higher pressures move the position of equilibrium to the right as there are less moles of gas and the equilibrium acts to counteract any external change.

  The higher the pressure, the more dangerous and more expensive the process is.

  200 atm is a compromise.
• The iron catalyst makes the reaction go faster but does not affect the yield.