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Learning About Haber Process – O Level Chemistry

production of ammonia from hydrogen and nitrogen in the haber process

Haber process is the industrial process used for the manufacture of ammonia from hydrogen and nitrogen.

Raw materials of Haber Process

Hydrogen and nitrogen are the raw materials required for the production of Haber Process.

Hydrogen can be obtained industrially from steam reforming.

Nitrogen can be obtained industrially from the fractional distillation of liquid air.

Reaction for production of ammonia

Ammonia is produced from hydrogen and nitrogen. The reaction is reversible and can be represented by the following equation:

N2 + 3H2 ⇌ 2NH3

Iron is used as a catalyst to speed up the rate of the reaction.

Industrial Condition used for production of ammonia

The conditions used for the production of ammonia are:

  • pressure of 200 atmosphere (atm)
  • temperature of 450 oC
  • iron as catalyst

Effect of temperature on yield of ammonia in Haber Process

N2 + 3H2 ⇌ 2NH3  , ΔH < 0 (exothermic)

The forward reaction is exothermic. Based on Le Chatelier’s principal, to shift the position of equilibrium to the right, it will favour a lower temperature. However, too low a temperature will result in a reaction that is too slow. Hence, a moderate temperature (in industrial terms) of about 450 oC is used.

Effect of pressure on yield of ammonia in Haber Process

If you look at the equation, the formation of ammonia involve converting 4 moles of gases to 2 moles of gases. A decrease in number of moles of gases will reduce pressure (assuming all other factors remain constant). To shift the position of equilibrium to the right (to produce more ammonia), higher pressure is needed.

There is a problem though. When pressure is too high, the equipment cost increases to build equipment that can cater to such high pressure. As such, industrially, a moderate pressure of 200 atm is used.

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