C3 Equilibrium Flashcards
What happens to the un-reacted gases?
Unreacted nitrogen and hydrogen are recycled.
When is equilibrium reached in a reaction in a closed system?
When a reversible reaction occurs in a closed system, equilibrium is reached when the reactions occur at exactly the same rate in each direction.
Explain the catalyst used in the Haber process.
The iron catalyst increases the rate of reaction but does not change the percentage yield
Describe the conditions used when ammonia is made in the Haber process.
Iron catalyst, high pressure, temperature in the region of 450°C.
Construct the word and the balanced symbol equation for the Haber process.
nitrogen + hydrogen →ammonia
N2 + 3H2 → 2NH3
Explain the pressure used in the Haber process.
High pressure increases the percentage yield of ammonia as there are less moles of gases in the products side of the equation.
How can you change the relative amounts of the substances in an equilibrium mixture?
The relative amounts of all the reacting substances at equilibrium depend on the conditions of the reaction.
How does changing the pressure affect a gaseous equilibrium?
In gaseous reactions, an increase in pressure will favour the reaction that produces the least number of molecules as shown by the symbol equation for that reaction.
In the Haber process, where do they get the nitrogen, N2 and the hydrogen, H2?
Nitrogen from the air. Hydrogen from the cracking of oil fractions or from natural gas.
How is the ammonia separated from the unreacted gases?
The ammonia is cooled below -40’c and it liquefies.
Explain the temperature used in the Haber process. (The forward reaction is exothermic.)
High temperature decreases the percentage yield of ammonia but high temperature gives a high rate of reaction; so 450°C is an optimum temperature to give a fast reaction with a sufficiently high percentage yield
How does lowering the temperature affect an equilibrium mixture?
If the temperature is lowered, the yield from the endothermic reaction decreases and the yield from the exothermic reaction increases.
How does increasing the temperature affect an equilibrium mixture?
If the temperature is raised, the yield from the endothermic reaction increases and the yield from the exothermic reaction decreases.
