c15 Using our resources Flashcards
What can ammonia be used to make?
fertilisers
, explosives and dyes.
What is the Haber process?
The industrial chemical process that makes ammonia by reacting nitrogen and hydrogen together.
The haber process is a ________ reaction
reversible
What is the formula for the haber process?
N2(g) + 3H2(g) ⇌ 2NH3(g)
How are the raw materials for the production of ammonia collected?
Nitrogen-Naturally present in the atmosphere
Hydrogen-Collected from Natural Gas
What are the steps of the Haber Process?
nitrogen (extracted from the air) and hydrogen (obtained from natural gas) are pumped through pipes
the pressure of the mixture of gases is increased to 200
atmospheres
the pressurised gases are heated to 450°C and passed through a tank containing an iron
catalyst
the reaction mixture is cooled so that ammonia
liquefies and can be removed
unreacted nitrogen and hydrogen are
recycled
What is the atom economy for the Haber process and why is it like this?
100% atom economy so no waste by-products formed in
reaction,
no pollution from by-products,
no energy required for their disposal
What happens to unreacted nitrogen and hydrogen in the Haber Process?
It gets recycled back into the reaction vessel to react to form Ammonia again
Why is 200 atmospheres used in HP?
When the pressure is higher the equilibrium shifts to the side with the least amount of gases- in this case to the side with ammonia- increasing the yield. However higher pressures are expensive and costly so 200 atms is chosen as a compromise
Why is an Iron catalyst used in HP?
An Iron catalyst speeds up the rate of the forward and reverse reactions equally. This reduces the time taken for the system to reach equilibrium but it does not affect the position of equilibrium or the yield of ammonia.
Using a catalyst in the Haber process means that a lower temperature can be used whilst keeping the rate of reaction high. A lower temperature helps to keep the yield high.
Why is a temperature of 450C chosen for HP?
When the temperature is increased, the position of equilibrium moves in the endothermic direction to reduce the temperature.
In the Haber process, the forwards reaction is
exothermic, so the reverse reaction is endothermic.
This means that as the temperature is increased, the position of equilibrium moves to the left, and the yield of ammonia decreases.
It may seem sensible to use a very low temperature in order to maximise the yield of ammonia but lower temperatures reduce the rate of reaction. The temperature chosen is a compromise between yield and rate.
