4.10.4 The Haber process and the use of NPK fertilisers Flashcards
What is the Haber process used for?
The Haber process is used to manufacture ammonia, which can be
used to produce nitrogen-based fertilisers
raw materials for haber process
nitroogen
hydrogen
where are nitrogen and hydrogen from
- Nitrogen is extracted from the air
* Hydrogen is obtained from natural gas.
Explain the Haber process
The purified gases are passed over a catalyst of iron at a
- high temperature (about 450°C)
- high pressure (about 200 atmospheres).
Some of the hydrogen and nitrogen reacts to form
ammonia.
The reaction is reversible so some of the ammonia
produced breaks down into nitrogen and hydrogen
On cooling, the ammonia liquefies and is removed.
The remaining hydrogen and nitrogen are recycled.
The haber process equation
nitrogen + hydrogen ⇌ ammonia
process of haber process
The purified gases are passed over a catalyst of iron at a high temperature and high pressure.
On cooling the ammonia liquefies (turns into a liquid) and is removed.
The remaining hydrogen and nitrogen are recycled.
The ammonia can be used to make nitrogen-based fertilisers
The conditions for the Haber process are:
- A temperature of 450oC
- A pressure of 200 atmospheres
- An iron catalyst
The reaction is reversible so…
some of ammonia breaks down into nitrogen and hydrogen.
The reaction is exothermic so..
there are more moles of gas on the left hand side of the reaction
when if the forward reaction favoured
This means the forward reaction is favoured if there is a high pressure and lower temperature.
Both of these will push the position of equilibrium to the right to maximise the yield
compromise
However, a low temperature would give a
slow rate of reaction, so a compromise
temperature of 450oC is used.
High pressures can be dangerous, lowering the
pressure increases safety.
why we use a compromise
Very high pressure and temperatures will also have a cost implication.
A compromise on temperature and pressure leads to reduced costs and a more economically viable product.
what does NPK stand for
Nitrogen
Phosphorus
Potassium
how is ammonium nitrate produced
Ammonium nitrate is a salt used as a fertiliser, produced
from the reaction between ammonia and nitric acid.
Preparation of ammonium sulfate from ammonia
solution and dilute sulfuric acid.
• Add known volume of dilute sulfuric acid to an
evaporating basin.
• Add known volume and concentration of
ammonia to the sulfuric acid.
• Test with universal indicator paper to ensure
neutral.
• Evaporate the solution slowly using Bunsen
burner to concentrate the solution.
• Cool until crystals form; dry the sample
