1. 1
   A plastics factory receives a delivery of ethene gas, C2H4, to use as a starting material for polymer production. Before use, the quality control laboratory confirms the identity of the sample using a simple chemical test.

   (a)

   Which feature of ethene's structure classifies it as an alkene?

   [1 mark]

   • AIt contains a carbon-carbon double bond
   • BIt contains only single carbon-carbon bonds
   • CIt contains an -OH group
   • DIt contains a -COOH group

   (b)

   The quality control laboratory adds a sample of the gas to aqueous bromine. Which observation would confirm that the sample is indeed an alkene?

   [1 mark]

   • AThe bromine water turns blue
   • BThe orange-brown bromine water remains unchanged
   • CA white precipitate forms immediately
   • DThe orange-brown bromine water turns colourless

   (c)

   Once confirmed, the ethene is reacted with hydrogen in the presence of a nickel catalyst. Name the type of reaction that occurs and identify the organic product formed.

   [2 marks]

   Total for question 1: 4 marks

2. 2
   An industrial chemical plant produces ethanol by reacting ethene with steam over an acid catalyst at high temperature and pressure, as an alternative to producing ethanol by fermentation.

   (a)

   Which type of reaction is this?

   [1 mark]

   • ANeutralisation
   • BSubstitution
   • CAddition
   • DFermentation

   (b)

   The plant manager compares this catalytic process with fermentation as a source of ethanol for industrial solvents. Which statement is a genuine advantage of the catalytic addition process over fermentation?

   [1 mark]

   • AIt uses a renewable raw material (glucose from plants)
   • BIt is a continuous process and produces a purer product more quickly
   • CIt requires no high-pressure equipment
   • DIt operates at low temperature, requiring no external energy input

   (c)

   State one disadvantage of producing ethanol by the catalytic addition of steam to ethene, compared with producing it by fermentation.

   [2 marks]

   Total for question 2: 4 marks

3. 3
   A curator restoring an old greenhouse notices that overripe fruit stored nearby appears to accelerate the ripening of other fruit in the same enclosed space. Modern research has since shown that this effect is due to ethene, an alkene gas released naturally by ripening fruit.

   (a)

   Describe the general formula of the alkene homologous series and confirm that ethene, C2H4, fits it.

   [3 marks]

   (b)

   The curator wants to prevent premature ripening in a storage room by removing any ethene gas that accumulates. Explain, in terms of bonding, why ethene is more reactive than an alkane of similar molecular size, and suggest, in general chemical terms, what type of reaction could be used to convert ethene gas into a less volatile liquid product for easier removal.

   [4 marks]

   Total for question 3: 7 marks

4. 4
   A medical device company wants to manufacture flexible plastic tubing from an alkene monomer, but must first source large quantities of the alkene, which are not directly available from crude oil in sufficient amount.

   (a)

   Explain how the company can obtain the alkene they need from crude oil fractions, and describe the chemical reason alkenes are suitable starting materials for making polymers.

   [6 marks]

   (b)

   Before committing to full-scale polymer production, the company also tests whether their alkene sample could instead be used to manufacture ethanol as a cheaper solvent for cleaning their equipment. Compare the catalytic addition of steam to the alkene with fermentation as methods of producing ethanol, and recommend which method would better suit a company that needs a fast, continuous, industrial-scale supply.

   [6 marks]

   Total for question 4: 12 marks

End of questions