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· Nitrogen and hydrogen are needed to make ammonia
· The nitrogen is easily obtained from air- 78% nitrogen
· The hydrogen comes from natural gas or from other sources like
crude oil
· Some of the nitrogen and hydrogen react to form ammonia
· Because the reaction is reversible, ammonia breaks down again into
hydrogen and nitrogen
· The reaction reaches an equilibrium
+heat…read more

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The Reaction is Reversible
· High pressures favour the forward reaction- 4 molecules of gas on the left hand
side for every 2 on the right hand side
· The pressure is set as high as possible to give the best percentage yield...
without making it too expensive to build, so it is 200 atmospheres (in the
· The forward reaction is exothermic- increasing the temperature will move the
equilibrium the wrong way (away from ammonia and towards N2 and H2)
· So, the yield of ammonia is greater at lower temperatures
· But, lower temperatures mean a lower rate of reaction
· 450°C ­compromise between maximum yield and speed of reaction
· The ammonia formed is a gas- cools in the condenser and is liquefied and
removed…read more

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Iron Catalyst
· The iron catalyst makes the reaction go faster which gets it to the
equilibrium proportions more quickly
· The catalyst doesn't affect the position of the equilibrium i.e. the
percentage yield
· Why is the catalyst important?
-without it, the temperature would have to be raised even further to
get a quick enough reaction... which would reduce the percentage
yield even further…read more

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