1. 1
   A geologist analyses a sample of crude oil extracted from a newly discovered oil field before it is sent to a refinery.

   (a)

   Which statement best describes crude oil?

   [1 mark]

   • AA mixture of a very large number of compounds, most of which are hydrocarbons
   • BA single pure hydrocarbon compound
   • CAn element made only of carbon
   • DA solution of carbon dioxide in water

   (b)

   Which two elements make up the hydrocarbon molecules found in crude oil?

   [1 mark]

   • ACarbon and oxygen only
   • BHydrogen and nitrogen only
   • CHydrogen and carbon only
   • DCarbon and sulfur only

   (c)

   Explain what is meant by the term 'hydrocarbon' and state how this relates to the composition of crude oil.

   [2 marks]

   Total for question 1: 4 marks

2. 2
   An oil refinery heats crude oil and passes it into a tall fractionating column to separate it into fractions with different uses.

   (a)

   Which physical process is used to separate crude oil into fractions at a refinery?

   [1 mark]

   • AFiltration
   • BFractional distillation
   • CElectrolysis
   • DNeutralisation

   (b)

   In the fractionating column, what happens to the hydrocarbons as they rise?

   [1 mark]

   • AThey evaporate further and never condense
   • BThey dissolve completely in each other and cannot be separated
   • CThey react with oxygen to form carbon dioxide
   • DThey condense at different temperatures according to their boiling points

   (c)

   Describe how fractional distillation separates crude oil into fractions.

   [2 marks]

   Total for question 2: 4 marks

3. 3
   A chemistry teacher asks students to justify why crude oil must be processed before its components can be used separately.

   (a)

   A student claims that crude oil is a single compound. State whether the student is correct, and describe the true composition of crude oil.

   [3 marks]

   (b)

   Describe, in detail, the process of fractional distillation used to separate the hydrocarbons in crude oil into fractions.

   [4 marks]

   Total for question 3: 7 marks

4. 4
   A team of engineers is commissioning a new refinery and must explain the science behind fractional distillation to trainee operators before the plant starts processing crude oil.

   (a)

   A new refinery is being designed to process crude oil into separate fractions for use as fuels and chemical feedstocks. Explain in detail how fractional distillation achieves this separation, referring to heating, the temperature gradient in the column, and condensation of vapours.

   [6 marks]

   (b)

   Explain why crude oil is described as a mixture rather than a single compound, and why understanding this is important for the design of fractional distillation.

   [6 marks]

   Total for question 4: 12 marks

End of questions