1. 1
   A brewery ferments glucose solution using yeast at around 30°C in a sealed vessel, producing an alcoholic drink.

   (a)

   Which functional group is present in the alcohol formed?

   [1 mark]

   • A-COOH
   • B-OH
   • C-COO-
   • D>C=C<

   (b)

   Why must the fermentation vessel be sealed to exclude air during this process?

   [1 mark]

   • ATo prevent oxygen entering, since oxygen would oxidise the ethanol formed to ethanoic acid
   • BTo prevent the yeast from reproducing too quickly
   • CTo keep the glucose solution at a constant pH
   • DTo stop carbon dioxide from being produced

   (c)

   Explain why the temperature of the fermentation vessel is kept at approximately 30°C rather than much higher or lower.

   [2 marks]

   Total for question 1: 4 marks

2. 2
   An industrial chemical plant produces ethanol by reacting ethene with steam, using a phosphoric acid catalyst at around 300°C and 60-70 atmospheres pressure.

   (a)

   What type of reaction is this?

   [1 mark]

   • AA fermentation reaction, since ethanol is the product
   • BA substitution reaction, because a hydrogen atom in ethene is replaced by an -OH group
   • CA combustion reaction, because ethene is burned in steam
   • DAn addition reaction, because steam adds across the carbon-carbon double bond in ethene

   (b)

   What is the role of the phosphoric acid in this industrial process?

   [1 mark]

   • AIt is a reactant that is used up during the reaction
   • BIt is a solvent that dissolves the ethene gas
   • CIt is a catalyst that speeds up the reaction without being used up
   • DIt provides the oxygen atom needed to form the -OH group

   (c)

   Compare this industrial method of making ethanol with the fermentation method, in terms of the raw material used and whether the process is continuous or batch.

   [2 marks]

   Total for question 2: 4 marks

3. 3
   A restaurant stores an open bottle of wine on the counter for several days. When a chef tastes the wine, it has developed a sour, vinegar-like taste.

   (a)

   Explain, in terms of a chemical reaction, why the ethanol in the wine has changed in this way.

   [3 marks]

   (b)

   Describe two other methods, besides leaving the wine exposed to air, by which ethanol can be oxidised, and state the product formed by burning ethanol completely in air.

   [4 marks]

   Total for question 3: 7 marks

4. 4
   A biofuel company is deciding whether to produce ethanol by fermentation of glucose from sugar cane or by the industrial reaction of ethene with steam.

   (a)

   Describe both processes in detail, including the conditions required for each, and discuss one advantage and one disadvantage of each method.

   [6 marks]

   (b)

   Evaluate which of the two ethanol production methods, fermentation or ethene hydration, is more sustainable in the long term, considering the raw materials used and the energy requirements of each process.

   [6 marks]

   Total for question 4: 12 marks

End of questions