The haber process Flashcards
What does the Haber process produce?
Ammonia (NH3).
What is ammonia used to make?
Fertilisers.
What is needed to make ammonia?
- Nitrogen.
- Hydrogen.
What is the reaction for making ammonia?
N2(g) + 3H2(g) ⇌ 2NH3 (g)
Where do we get the nitrogen from that we use to make ammonia?
It is obtained easily from the air, which is 78% nitrogen and 21% oxygen.
Where do we get the hydrogen from that we use to make ammonia?
It comes from natural gas or from other sources like crude oil.
What does it mean that the reaction to make ammonia is reversible?
That it occurs in both directions, so ammonia breaks down again into nitrogen and hydrogen, and the reaction reaches equilibrium.
What are the industrial conditions needed to make ammonia?
- Pressure: 200 atmospheres.
- Temperature: 450’c.
- Catalyst: Iron.
Because the reaction is reversible, what is there to be made?
A compromise.
To get more product what do we do?
Increase the pressure, as higher pressures favour the forward reaction.
Why do higher pressures favour the forward reaction?
As for every four molecules of gas on the left-hand side, there are two molecules on the right hand side.
Why is the pressure set as high as possible, but not too high?
To get the best percentage yield, without making the plant too expensive to build (we use 200 atmospheres pressure).
What type of reaction is the forward reaction?
Exothermic.
What does it mean that the forward reaction is exothermic?
That increasing the temperature will move the equilibrium the wrong way, away from ammonia towards N2 and H2.
When is the yield of ammonia greater?
At lower temperatures.
