Ammonia Flashcards
Haber process
Method of reacting Hydrogen (H2) and nitrogen (N2) to make ammonia (NH3).
3H2 + N2 (reversible arrow) 2NH3
Nitrogen is obtained from the air
Hydrogen is obtained from natural gas
On cooling, the ammonia liquefies and is removed.
The remaining hydrogen and nitrogen are recycled.
Haber process condition - why these choose
Conditions
• Iron catalyst
• High temperature (450 C)
• High Pressure (200 atm)
Optimal conditions are a compromise to produce the most equilibrium yield and at satisfactory rate of reaction.
High or low temperature would be the best condition for the Haber process
Low temperature
High or low pressure would be the best condition for the Haber process
High pressure
Why is high pressure not use in the Haber process
uses a lot of energy to maintain high pressure
Require specialised equipment
Why is High temperature use in the Haber process
increase rate of reaction
Equilibrium
A reversible reaction in a closed system (sealed vessel).
Occurs because the rate of the forward reaction is equal to the rate of the reverse reaction.
Closed system
Sealed vessel where nothing can enter or leave the reaction vessel.
Increasing temperature of an equilibrium
The yield from the endothermic reaction increases and the yield from the exothermic reaction decreases.
Equilibrium shift towards the endothermic reaction.
Decrease temperature of an equilibrium
The yield from the endothermic reaction decreases and the yield from the exothermic reaction increases
Equilibrium shift towards the exothermic reaction.
Increasing pressure for gases
An increase in pressure will favour the reaction that produces the least number of molecules as shown by the symbol equation for that reaction.
Example
3H2 + N2 (reversible arrow) 2NH3
Reactants total = 4 molecules (3 hydrogen + 1 Nitrogen)
Product total = 2 molecules (2 ammonia)
Increasing pressure shifts towards the right increasing ammonia
