1. 1
   A fertiliser factory manufactures ammonium nitrate by reacting ammonia gas with nitric acid in a large neutralisation reactor. The molten ammonium nitrate produced is cooled, dried and formed into small granules, which are then bagged and sold to farms as a nitrogen-rich fertiliser.

   (a)

   Which pair of elements, in addition to hydrogen, must be present in the compound ammonium nitrate?

   [1 mark]

   • ANitrogen and oxygen
   • BNitrogen and sulfur
   • CPhosphorus and oxygen
   • DPotassium and sulfur

   (b)

   What type of reaction takes place between ammonia and nitric acid in the reactor?

   [1 mark]

   • APrecipitation
   • BNeutralisation
   • CThermal decomposition
   • DElectrolysis

   (c)

   (i) Write a word equation for the reaction between ammonia and nitric acid. (ii) State why the product of this reaction is useful as a fertiliser.

   [2 marks]

   Total for question 1: 4 marks

2. 2
   A farmer growing wheat on a small family farm wants to choose a fertiliser that will improve the yield of the crop. The farmer selects an NPK fertiliser containing ammonium phosphate and potassium chloride, and spreads it across the field before the growing season begins.

   (a)

   What do the letters N, P and K stand for in an NPK fertiliser?

   [1 mark]

   • ANitrogen, platinum, potassium
   • BNitrogen, phosphorus, calcium
   • CNickel, phosphorus, potassium
   • DNitrogen, phosphorus, potassium

   (b)

   Which compound in the fertiliser supplies potassium to the soil?

   [1 mark]

   • AAmmonium phosphate
   • BAmmonium nitrate
   • CPotassium chloride
   • DCarbon dioxide

   (c)

   Suggest why the farmer chooses a fertiliser that supplies all three of nitrogen, phosphorus and potassium, rather than just one of these elements.

   [2 marks]

   Total for question 2: 4 marks

3. 3
   In the early 20th century, chemists developed an industrial process to manufacture ammonia from nitrogen and hydrogen gases, which allowed nitrogen-based fertilisers to be produced on a large scale for the first time. This ammonia was later reacted with sulfuric acid to manufacture solid ammonium sulfate fertiliser, which could be transported and stored easily.

   (a)

   Explain why this development was historically significant for global food production.

   [3 marks]

   (b)

   Ammonium sulfate fertiliser is manufactured by reacting ammonia with sulfuric acid. (i) Write a balanced symbol equation for this reaction. (ii) State the name of the type of reaction taking place. (iii) Explain, in terms of atoms, why the equation you have written must be balanced.

   [4 marks]

   Total for question 3: 7 marks

4. 4
   An international agricultural research group is investigating how manufactured NPK fertilisers, containing ammonium salts and nitrates, support global food production. The group is comparing the industrial manufacture of ammonium nitrate with older, less efficient methods of supplying nutrients to soil.

   (a)

   Explain the importance of nitrogen, phosphorus and potassium to plant growth, and describe how ammonium salts and nitrates act as sources of nitrogen in these fertilisers.

   [6 marks]

   (b)

   Ammonium nitrate fertiliser is manufactured industrially by reacting ammonia with nitric acid. Describe the industrial manufacture of ammonium nitrate, including the raw materials used, the type of reaction taking place, and why manufacturing fertiliser in this way benefits large-scale food production.

   [6 marks]

   Total for question 4: 12 marks

End of questions