The Haber Process Flashcards
(19 cards)
What is the Haber process used for?
To make nitrogen based fertilisers.
What is the symbol equation for ammonia?
N2 + 3H2 ⇌ 2NH3 (+heat)
Why is this reaction well suited for an industrial scale?
The reactants aren’t too difficult/ expensive to obtain
What pressure is the reaction conducted at?
200 atm (atmospheres)
What temperature is the industrial reaction to produce ammonia done at?
450 degrees
What catalyst does the reaction use?
An iron catalyst
Where is the nitrogen obtained from?
The air
What is the percentage of nitrogen in the air?
78%
Where is the Hydrogen obtained from?
Reacting methane (from natural gas) with steam to form hydrogen and CO2
Why is the Haber process so important?
The ammonia produced is used in a lot of things such as fertilisers allow us to grow food.
What is the 1st step of the process?
Hydrogen and nitrogen are fed into a reactor/reaction vessel (where the temp and conditions are kept as mentioned above). Here, the gases are free to pass over trays of the iron catalyst.
What happens under these conditions?
The nitrogen and hydrogen will react to form ammonia. However, as it’s a reversible reaction, the mixture will still contain a lot of nitrogen and hydrogen
What ratio are the Hydrogen and Nitrogen mixed in?
3:1 H2:N2
What is done to separate the mixture of ammonia, nitrogen and hydrogen?
As the ammonia has a lower boiling point than the other 2, the mixture is passed into the condenser which is colder than the reactor, so it cools the reactants down. The gaseous ammonia condenses into liquid ammonia.
What happens to the hydrogen and nitrogen?
As a result of their higher boiling points, they will stay gaseous and be recycled back into the reaction mixture.
The Haber process is in dynamic equilibrium …
the forwards and backwards reactions keep going once equilibrium is reached
What can ammonia be used to make?
ammonium nitrate
Why is the temperature 450 degrees?
The reaction is exothermic so a lower temp would mean the forward reaction is favoured resulting in higher percentage yield. However, a higher temp is needed for a higher rate of reaction so 450 is a compromise. Also a really high temp is costly to maintain so 450 is again a compromise.
Why is the pressure 200 atm?
A higher pressure is needed for a higher % yield as there’re fewer molecules of product than reactant so a higher pressure will push the equilibrium to the right. A higher pressure will also achieve a higher RoR But, the pratical considerations of cost and safety mean 200atm is the best pressure to be used.
