The Haber process and the use of NPK fertilisers

• What is the name and chemical formula of the substance made in the Haber process?

  Ammonia, NH3.
• What are the two raw materials used in the Haber process?

  Nitrogen and hydrogen
• Where does the nitrogen for the Haber process come from?

  Fractional distillation of air.
• Where does the hydrogen for the Haber process come from?

  Natural gas.
• What is the word equation for the production of ammonia in the Haber

  process?

  Nitrogen + hydrogen --> ammonia
• What is the balanced symbol equation for the production of ammonia in the

  Haber process?

  N2 + 3H2 --> 2NH3
• In the Haber process, what pressure is used in the compressor?

  200 atm
• In the Haber process, what temperature is used in the reactor?

  450oC
• In the Haber process, what catalyst is used in the reactor?

  Powdered iron.
• In the Haber process, why is the catalyst powdered?

  To increase surface area to volume ratio and increase rate.
• What happens to unreacted nitrogen and hydrogen in the Haber process?

  They remain as gases and can be recycled
• How is ammonia separated from unreacted nitrogen and hydrogen in the Haber process?

  It is cooled in a condenser and turns into a liquid.
• In the Haber process, why is the forwards reaction exothermic?

  Because heat energy is lost to the surroundings.
• In the Haber process, why might alternative reaction conditions be used?

  Depends on availability of raw materials, their cost and the cost of energy.
• In the Haber process, how could increased cost of raw materials be offset?

  By lowering operating temperatures or pressures.
• What three elements are used in NPK fertilisers?

  Nitrogen, phosphorous and potassium
• Why are the elements used in NPK fertilisers usually present as salts?

  So they dissolve in water and can be absorbed by plant roots.
• What is the chemical formula of ammonium nitrate?

  NH3NO3
• What is the chemical formula of potassium phosphate?

  K3PO4
• Formulation


  Mixtures designed with a precise purpose in mind. Each component is present in precisely measured quantities to meet the required function.
• How is ammonium nitrate made for use in NPK fertiliser?

  Ammonia from the Haber process is reacted with nitric acid.
• Write a balanced symbol equation for the formation of ammonium nitrate

  used in fertiliser.

  NH3 + HNO3 --> NH4NO3
• What three compounds used in production of fertilisers are obtained by mining?

  Potassium chloride, potassium sulfate and insoluble phosphate rock.
• In NPK fertilisers, phosphate rock cannot be used directly as a source of

  phosphorous, explain why.

  It is insoluble and cannot be absorbed by plant roots.
• How can phosphate rock be treated so it can be used in fertilisers?

  By reacting it with nitric acid, phosphoric acid or sulfuric acid.
• Name the products formed from reaction of phosphate rock with nitric acid.

  Phosphoric acid and calcium nitrate
• Name the products formed from reaction of phosphate rock with phosphoric acid.

  Calcium phosphate (triple superphosphate).
• Name the products formed from reaction of phosphate rock with sulfuric acid.

  Calcium phosphate and calcium nitrate (single superphosphate).
• Why do labels on fertilisers show the precise proportions of NPK in the fertiliser?

  Because fertilisers are formulations.
• A label on a fertiliser has the following information: NPK value = 14:11:11. What does this mean?

  The ratio of nitrogen to phosphorous to potassium.
• Why does a farmer need to know the ratio of NPK in fertiliser?

  So they can match different fertilisers to their own crops requirements, different crops require different ratios of NPK.
• Why are salts with a greater % by mass of nitrogen, phosphorous and/or

  potassium preferred?

  They are more beneficial to a farmer
• Which of these salts would be more beneficial to a farmer, NH4NO3 or NH4Cl?

  NH4NO3 because it contains a higher percentage by mass of nitrogen.