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The Haber process
- main use of ammonia is to make fertiliser.... fertiliser increase the yield of crops
and are very important in making sure that we can grow enough food to feed
everyone on the planet
- Ammonia is made by the reaction of nitrogen and hydrogen
- Nitrogen is obtained by fractional distilation of
liquified air (78% nitrogen) hydrogen often made
from natural gas (methane or other souces like oil)
- The reaction between nitrogen and hydrogen to make ammonia
is slow and reversible...this produces a very low yield of
ammonia
- Haber came up with a process to produce large
amounts of ammonia from this reaction by changing
the conditions to move the equilibrium position of the
reaction futher to the right and speed it up
- Hydrogen and nitrogen are passed over an iron catalyst at a pressure of 200
atmospheres and a tempof 450 degrees celcius. These are the optimum conditions
for making ammonia
- The temp of 450 os used as a compromise. the forward reaction is
exothermic and lower temp give higher yield of ammonia
....HOWEVER this reaction is slow and higher temps are needed to
produce ammonia at a good rate ; 450 is used as a compromise to
strike a balance between the yield and the rate of reaction
- The pressure of 200 is also a compromise... as there are
fewer gas molecules on the right of the equation...higher
pressure gives more ammonia .....HOEVER high pressure
is very expensive ; large amounts of energy are needed to
create the high pressure and the apparatus needed to
withstand high pressues is very expensive ... 200
atmospheres is used as a compromise between cost and
yield
- Iron - catalyst. The catalyst does not change the yield of
ammonia but it increases the rate of reaction
- Iron - catalyst. The catalyst does not change the yield of
ammonia but it increases the rate of reaction
- The pressure of 200 is also a compromise... as there are
fewer gas molecules on the right of the equation...higher
pressure gives more ammonia .....HOEVER high pressure
is very expensive ; large amounts of energy are needed to
create the high pressure and the apparatus needed to
withstand high pressues is very expensive ... 200
atmospheres is used as a compromise between cost and
yield
- The temp of 450 os used as a compromise. the forward reaction is
exothermic and lower temp give higher yield of ammonia
....HOWEVER this reaction is slow and higher temps are needed to
produce ammonia at a good rate ; 450 is used as a compromise to
strike a balance between the yield and the rate of reaction
- Hydrogen and nitrogen are passed over an iron catalyst at a pressure of 200
atmospheres and a tempof 450 degrees celcius. These are the optimum conditions
for making ammonia
- Haber came up with a process to produce large
amounts of ammonia from this reaction by changing
the conditions to move the equilibrium position of the
reaction futher to the right and speed it up
- Nitrogen is obtained by fractional distilation of
liquified air (78% nitrogen) hydrogen often made
from natural gas (methane or other souces like oil)
- The forward reaction is exothermic and so lower temp and
higher yield of ammonia. more gas molecules on the left of the
equilibrium so the higher the pressure the higher the yield of
ammonia
- After the reaction the equilibrium mixture is cooled.
ammonia has a higher boiling point than hydrogen
and nitrogen and so will liquefy first as the mixture is
cooled . Liquid ammonia is then removed from the
mixture and the left over nitrogen and hydrogen is
recycled to make more ammonia
- Ammonia production requires massive amounts of energy. The haber process provides
the optimum conditions to ensure that energy is used efficently. efficent use of energy
saves money and has less environmental impact
- Ammonia production requires massive amounts of energy. The haber process provides
the optimum conditions to ensure that energy is used efficently. efficent use of energy
saves money and has less environmental impact
- many industrial processes involve equilibrium reactions.
as with the haber process the reaction conditions
chosen in each case are a compromise between
geeting a good yield, having the reaction happen quickly
and keeping the energy input down whilst minimising
the impact on the environment
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