Dynamic Equilibria

5.19C Describe the Haber process as a reversible reaction between nitrogen and hydrogen to form ammonia
  • The reaction is reversible so ammonia breaks down again into nitrogen and hydrogen.

NITROGEN + HYDROGEN ⇌ AMMONIA

5.20C Predict how the rate of attainment of equilibrium is affected by: changes in temperature, changes in pressure, changes in pressure, changes in concentration, use of a catalyst

*see Topic 4- Reversible rections and equilibria notes

  • Rate of attainment of equilibrium is increased with the use of a catalyst, because it increases the rate of reaction for both the forward and backward reactions
 5.21C Explain how, in industrial reactions, including the Haber process, conditions used are related to: the availability and cost of raw materials and energy supplies, and the control of temperature, pressure and catalyst used produce an acceptable yield in an acceptable time
  • For the Haber process – the purified gases are passed over a catalyst of iron at a high temperature (about 450 °C) and a high pressure (about 200 atmospheres).
    • High temperatures and pressures are desired for industrial reactions to increase the rate of reaction
    • But, one of these could mean a decrease in yield, therefore a compromise is required to ensure a fast rate of reaction and a high yield of products
    • Catalyst is used because of the effect of having an increased rate of reaction, however they are also expensive
    • High temperatures and pressures can be expensive and dangerous as well (particularly pressures)
5.22C Recall that fertilisers may contain nitrogen, phosphorus and potassium compounds to promote plant growth
  • Compounds of nitrogen, phosphorus and potassium are used as fertilisers to improve agricultural productivity
  • NPK fertilisers contain compounds of all three elements
5.23C Describe how ammonia reacts with nitric acid to produce a salt that is used as a fertilizer
  • Ammonia can be used to manufacture ammonium salts with nitric acid
    • i.e. ammonium nitrate
    • Ammonia acts as a base
5.24C Describe and compare: the laboratory preparation of ammonium sulfate from ammonia solution and dilute sulfuric acid on a small scale and the industrial production of ammonium sulfate, used as a fertiliser, in which several stages are required to produce ammonia and sulfuric acid from their raw materials and the production is carried out on a much larger scale (details of the industrial production of sulfuric acid are not required)
  • In the lab
    • Measuring cylinder to measure a particular volume of an alkali solution
    • Burette to add acid a little at a time until the alkali has been neutralized
    • Filter funnel to remove solid crystals of fertiliser after evaporation some of the water from the neutral fertiliser solution
    • SMALL scale
  • In industry
    • LARGE scale
    • Many stages required