C3.5 Production Of Ammonia Flashcards
What is equilibrium in a reversible reaction?
When the amounts of reactants and products reach a certain balance.
How is equilibrium reached in a reversible reaction?
The reactions are still taking place but both the forward and backwards reactions are occuring at the same rate so they cancel each other out.
What effect does temperature have on a reversible reaction?
- Increased temperature = the endothermic reaction increases to use up the extra heat
- Decreased temperature = the exothermic reaction increases to give out extra heat
What effect does pressure have on a reversible reaction?
Increased pressure = an increase in the reaction which produces less volume (which has less gaseous molecules)
Decreased pressure = an increase in the reaction which produces more volume (which has more gaseous molecules)
What effect do catalysts have on a reversible reaction?
They do not change the position of equilibrium, they only make it quicker to get there.
Write the symbol equation for the reaction that takes place in the Haber process.
N2 +3H2 ——–> 2NH3
What is the Haber process?
An industrial process used to make ammonia.
What is ammonia used for?
Fertiliser, explosives
What are the reactants in the Haber process? Where do they come from?
Nitrogen - from the air
Hydrogen - from natural gas
What are the industrial conditions for the Haber process?
Temperature = 450 degrees Pressure = 200 atmospheres Catalyst = Iron
Why is the pressure what it is in the Haber Process?
- Higher pressures favour the forward reaction
- So the pressure is increased as much as possible to give the best percentage of yield without it being too expensive
Why is the temperature what it is in the Haber Process?
- The forward reaction is exothermic, so increasing the temperature would actually move the position of equilibrium the wrong way (towards making hydrogen and nitrogen instead of ammonia as that is the endothermic reaction which increases as temperature increases)
- However, lowering the temperature would lower the rate of reaction.
- The 450 degrees is a compromise between a maximum yield and the speed of reaction. It is better to wait a shorter amount of time for a lesser percentage yield.
What happens to the ammonia gas formed?
As it cools in the condenser it liquefies and is removed
What is the ‘position of equilibrium’?
The percentage yield - how much product is made compared to how much reactants there are when equilibrium is reached.
What happens to the unused nitrogen and hydrogen in the Haber Process?
They are recycled
