1. 1
   A mining company processes a mixture of insoluble rock fragments suspended in a solution containing dissolved copper sulfate, and needs to obtain solid, pure copper sulfate crystals from this mixture.

   (a)

   Which separation technique should be used first to remove the insoluble rock fragments from the solution?

   [1 mark]

   • AFiltration
   • BCrystallisation
   • CSimple distillation
   • DFractional distillation

   (b)

   After removing the rock fragments, the company wants to obtain solid copper sulfate crystals from the remaining solution. Which technique should be used next?

   [1 mark]

   • AFiltration
   • BCrystallisation
   • CPaper chromatography
   • DFractional distillation

   (c)

   Describe how the company should carry out crystallisation to obtain pure, solid copper sulfate crystals from the filtered solution.

   [2 marks]

   Total for question 1: 4 marks

2. 2
   A desalination plant wants to obtain pure water from seawater, which is a solution of various dissolved salts in water, to supply drinking water to a coastal city.

   (a)

   Which technique is most suitable for obtaining pure water (the solvent) from this solution?

   [1 mark]

   • APaper chromatography
   • BCrystallisation
   • CSimple distillation
   • DFiltration

   (b)

   Engineers at the plant confirm the purity of the collected water sample by measuring its boiling point. Which observation would indicate the water is pure?

   [1 mark]

   • AIt does not boil at all
   • BIt boils above 100 °C at standard atmospheric pressure
   • CIt boils over a range of temperatures rather than at one fixed temperature
   • DIt boils at exactly 100 °C at standard atmospheric pressure

   (c)

   Suggest why testing both the melting point and boiling point of a sample gives a more reliable assessment of its purity than testing only one of these properties.

   [2 marks]

   Total for question 2: 4 marks

3. 3
   A whisky distillery wants to separate ethanol from a fermented mixture that also contains water and various other soluble compounds, all with different boiling points. The distillery also wants to check the purity of the final ethanol product before bottling.

   (a)

   Explain why simple distillation would not be suitable for this task, and name the appropriate technique instead.

   [3 marks]

   (b)

   Describe how fractional distillation would be used to separate the ethanol from the fermented mixture, and explain how the distillery could then use melting point and boiling point data to assess the purity of the collected ethanol.

   [4 marks]

   Total for question 3: 7 marks

4. 4
   A laboratory receives a muddy sample of rock salt (impure sodium chloride mixed with insoluble sand and clay) and is asked to produce a sample of pure, dry sodium chloride crystals.

   (a)

   Describe, step by step, the full sequence of separation and purification techniques the laboratory should use, and explain the purpose of each step in terms of the properties of the substances involved.

   [6 marks]

   (b)

   Once the sodium chloride crystals have been produced, the laboratory is asked to confirm they are genuinely pure and to explain, in general terms, how they would choose the correct separation technique if instead given a mixture of two miscible liquids with very similar boiling points, rather than a solid-liquid mixture. Discuss both parts of this task.

   [6 marks]

   Total for question 4: 12 marks

End of questions