the Haber process

• The Haber process is used to make ammonia from hydrogen and nitrogen
• nitrogen + hydrogen -> ammonia (+heat)
• the reaction is well suited for industrial scale as the reactants aren't too expensive to obtain
• 1 - the nitrogen is obtained easily from the air (70% nitrogen)
• 2 - the hydrogen mainly comes from reacting methane (from natural gas) with steam to form hydrogen and carbon dioxide
• 3 - the reactant gases are passed over an iron catalyst to increase surface area. this does not effect equilibrium . a high temperature and high pressure, in the compressor, are used
• 4 - because the reaction is reversible, some of the ammonia produced converts back intro hydrogen and nitrogen again. it reaches a dynamic equilibrium
• 5 - the ammonia is formed as a gas but as it cools in the condenser it liquifies and is removed. the unused oxygen and nitrogen are recycled
• 6 - the ammonia is produced can be used to make ammonium nitrate
• the forward reaction in the Haber process is exothermic. increasing the temperature will move the equilibrium the wrong way- away from the ammonia and towards nitrogen and hydrogen so the yield of ammonia would be greater at lower temperatures
• lower temp mean lower rate of reaction , equilibrium will be reached more slowly
• higher pressures move the position of equilibrium towards the products since there are four molecules of gas on the left hand side for every two molecules on the right . increasing pressure maximises percentage yield. also increases rate of reaction
• the pressure is set as high as possible. Iron catalyst make the reaction go faster, by increasing surface area but doesn't affect the equilibrium
• reaction vessel is at 450 degrees c and 200 atm pressure
• in the condenser , the ammonia is condensed as it has a much lower boiling point than nitrogen and hydrogen
• because the reaction is exothermic, we need lower temperature to favour the forward reaction and achieve a higher percentage yield. However, need a high temperature to reach high rate of reaction as particles need lots of kinetic energy to collide and react
• a compressor is used at high pressure to increase more frequent collisions of reactants
• generating heat is expensive
• there are 4 moles of reactants and 2 moles of products, so high pressure pushes equilibrium right
• high pressure is dangerous and expensive