1. 1
   A tanker delivers crude oil to a refinery, where it is heated and fed into a fractionating column. The column is hot at the bottom and progressively cooler towards the top.

   (a)

   Which statement correctly describes how the column separates the oil?

   [1 mark]

   • AFractions with low boiling points condense near the bottom and fractions with high boiling points rise to the top
   • BFractions with low boiling points rise higher up the column before condensing, while fractions with high boiling points condense lower down
   • CAll fractions condense at the same height because crude oil is a pure substance
   • DThe column separates fractions by their colour rather than their boiling point

   (b)

   Which of these fractions collected from the column would have the shortest hydrocarbon chain lengths, the lowest viscosity and the palest colour?

   [1 mark]

   • ABitumen
   • BFuel oil
   • CRefinery gases
   • DDiesel

   (c)

   State two named fractions produced by this fractional distillation process and give one everyday use for each.

   [2 marks]

   Total for question 1: 4 marks

2. 2
   City authorities are investigating rising levels of acid rain near an industrial estate where fuel oil containing sulfur impurities is burned continuously in furnaces.

   (a)

   Which gas released from burning this fuel oil directly causes acid rain?

   [1 mark]

   • ACarbon dioxide
   • BWater vapour
   • CNitrogen
   • DSulfur dioxide

   (b)

   The furnaces reach very high temperatures during combustion. Which pair of gases from the air react at these high temperatures to form oxides of nitrogen, which also contribute to acid rain?

   [1 mark]

   • ANitrogen and oxygen
   • BCarbon dioxide and oxygen
   • CNitrogen and hydrogen
   • DOxygen and argon

   (c)

   Explain how the sulfur dioxide produced by these furnaces leads to the formation of acid rain in the local environment.

   [2 marks]

   Total for question 2: 4 marks

3. 3
   A patient is brought into hospital after being found unconscious in a garage with a car engine running in an enclosed space. Doctors suspect carbon monoxide poisoning from incomplete combustion of the petrol.

   (a)

   Explain why carbon monoxide is formed when petrol burns in this enclosed garage rather than carbon dioxide.

   [3 marks]

   (b)

   Explain why carbon monoxide is dangerous to the patient's health, in terms of its effect on the blood.

   [4 marks]

   Total for question 3: 7 marks

4. 4
   A refinery finds that it produces far more of the long-chain fractions such as fuel oil and bitumen than customers demand, while demand for shorter-chain fractions such as gasoline and refinery gases far exceeds the supply obtained directly from fractional distillation. The refinery decides to use catalytic cracking to address this imbalance.

   (a)

   Describe the process of catalytic cracking, including the conditions used, and explain how it converts long-chain hydrocarbons into more useful products.

   [6 marks]

   (b)

   Evaluate why cracking is considered economically necessary for a refinery, referring to the relationship between the fractions produced by fractional distillation and the fractions actually demanded by consumers.

   [6 marks]

   Total for question 4: 12 marks

End of questions