The Haber process

The Haber Process
The manufacture of Ammonia
N 2(g) + 3H2(g) 2NH3(g) H= -92kjmol-1
Equilibrium Conditions:
Temperature of 400C ­ 450C (700K):
- As the reaction is exothermic (-)­H/T will be positive
- Increasing the temperature will make H/T (Ssurr) less
positive
- Reducing Stotal and value of Kp falls.
- Hence K<Q, the system will try to decrease Q by making more
reactants favouring the backward reaction and so a lower yield
would be achieved. (However a catalyst is used to gain a
reasonable yield)…read more

Iron catalyst (traces of Al2O3 and K2O):
· An iron catalyst is used so that a reasonable rate and
reasonable yield is achieved at a temperature of
700K.
· Because at room temperature with no catalyst the
rate would be too slow and no products would form.
Also at high temperatures without a catalyst would
result in a lower yield of ammonia.…read more

Pressure of 200atm:
- An increase in pressure increases yield as in a more
compact environment more collisions would occurs.
- Increasing pressure would cause the denominator
(4square) to increase more than the numerator
(2squared), hence it will make the partial pressure
expression smaller K>Q. In order to make Kp = Q the
system will react to increase Q by making more
ammonia. Equilibrium shifts to the right increasing yield
of NH3.…read more

Atom Economy:
The percentage efficiency of reactants to products
·Under the normal conditions only 30% of H2 is converted to
ammonia. As the rate of reaction is still too slow for
equilibrium to be reached.
·To ensure all the hydrogen is converted to ammonia. The
gases leaving the catalyst chamber are cooled, removing
ammonia which is then liquefied and separated from
unreacted hydrogen and nitrogen.
·The unreacted hydrogen and nitrogen is recycled and reused
to give a higher atom economy about 98% and reduce
wastage products.…read more