Unit 18 Assignment D
D: Understand physical chemistry concepts and how industry controls chemical reac:ons.
Controlling industrial reac:ons
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, The Haber process
The Haber process is used to process a chemical reac:on to manufacture ammonia by using nitrogen
gas and hydrogen gas as reactants. Ammonia is used in many parts of life, such as producing plas:cs,
dyes, and pharmaceu:cals, etc. the reac:on itself is a reversible reac:on and the produc:on of
ammonia is an exothermic reac:on, meaning it gives off heat during the chemical reac:on itself as
new bonds are formed.
Below is the method of the Haber process:
1. Nitrogen (from the atmosphere) and hydrogen (from natural gas) are pumped through
pipelines.
2. The pressure of the gas combina:on is adjusted to 200 atmospheres.
3. The pressurised gases are then heated to 450°C and then fed through an iron catalyst tank.
4. The reac:on mixture is chilled to allow the ammonia to liquefy and be extracted.
5. the unreacted nitrogen and hydrogen that has reacted is recycled.
How are gasses cooled a1er the reac3on?
Nitrogen and hydrogen that is sourced from natural gasses to produce ammonia are recycled if there
is are s:ll unused reactants, both nitrogen and hydrogen would be recycled so that the remaining
reactants can be used up, each :me the chemical reac:on occurs around 15% of the reactants are
used, so recycling them so that all of the reactants can be used is a way to reduce costs and
emissions entering the atmosphere. Ammonia can be cooled once the reac:on is over as it is easily
liquified under low pressure, as the temperature is lowered in the condenser chamber this would
cause the ammonia to cool and would become a liquid, which is easier and safer to transport. As
temperatures can get as high as 400-450 °C it would be important for both the unreacted gasses to
be cooled and for the ammonia gas to be cooled as this would increase the percentage yield. The
main reason why gasses are cooled aUer the reac:on, is so that ammonia can be separated from the
mixture.
For a gas to change state to a liquid, this would make it easier for ammonia to be stored and
transported, a cooling in gasses causes pressure to decrease and the molecules also slow down. As
this would reduce the kine:c energy of the ammonia liquid this would make it easier for it to be
separated from the unused reactants.
The use of an iron catalyst and why it is powdered
The actual Haber process itself would take too long for the reactants to actually react, this not cost
efficient as too much :me would be taken to produce ammonia, the use of an iron catalyst is meant
to speed up the rate of reac:on and also reduces the ac:va:on energy of the chemical reac:on. As
the ac:va:on energy is the minimum energy that is needed for reactant molecules to undergo a
chemical reac:on and for a product to be yielded, a catalyst would reduce ac:va:on energy and
would speed up the rate of reac:on.
Using a catalyst is meant to speed up the rate of reac:on, it is not consumed during the chemical
reac:on. It does not affect the posi:on of the equilibrium of a reac:on, as using iron as a catalyst is
cheap and effec:ve it is the favoured for its uses as a catalyst in the Haber process. As iron powder
has a greater surface area and as its volume stays the same, meaning that a high volume of iron
powder can be used and would speed up the reac:on due to its greater surface area as solid iron has
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