Industrial Processes & Equilibrium (Oxford AQA IGCSE Chemistry)

Industrial Processes

• The effect of temperature and pressure on the position of equilibrium, as well as reaction rates help determine the optimum conditions in industrial processes

• For example, a lower temperature might result in a higher yield of product, but the rate of reaction will be slow

  • A compromise temperature would be used to obtain a good yield of product at a reasonable rate

• Similarly, a high pressure might also result in a higher yield of product, but there are safety considerations and the equipment is expensive

  • A compromise pressure would be used sto obtain a good yield of product without being too costly or unsafe

• The Haber process is a good example of showing how different factors are considered when determining the optimum temperature and pressure to be used

N₂ (g) + 3H₂ (g) ⇌ 2NH₃ (g)

Temperature: 450ºC

• A higher temperature would favour the reverse reaction as it is endothermic (takes in heat)

  • So, a higher yield of reactants would be made

• If a lower temperature is used it favours the forward reaction as it is exothermic (releases heat)

  • So, a higher yield of products will be made

  • However, at a lower temperature the rate of reaction is very slow

• So, 450ºC is a compromise temperature between having a lower yield of products but being made more quickly

Pressure: Atmospheric pressure (200 atm)

• A lower pressure would favour the reverse reaction as the system will try to increase the pressure by creating more molecules (4 molecules of gaseous reactants)

  • So, a higher yield of reactants will be made

• A higher pressure would favour the forward reaction as it will try to decrease the pressure by creating less molecules (2 molecules of gaseous products)

  • So, a higher yield of products will be made

  • However, high pressures can be dangerous and very expensive equipment is needed

• So, 200 atm is a compromise pressure between a lower yield of products being made safely and economically