1. 1
   A brewery ferments aqueous glucose using yeast to produce ethanol, C2H5OH, for its beverages, carefully controlling the fermentation conditions to maximise yield.

   (a)

   Which functional group identifies ethanol as an alcohol?

   [1 mark]

   • A-OH
   • B-COOH
   • CC=C
   • D-Cl

   (b)

   The brewers must keep the fermentation vessel sealed to exclude air. Under which conditions does fermentation of glucose by yeast take place?

   [1 mark]

   • A300 °C, 6000 kPa, in the presence of an acid catalyst
   • B25-35 °C, in the absence of oxygen
   • C450 °C, 20000 kPa, with an iron catalyst
   • D25-35 °C, with a plentiful supply of oxygen

   (c)

   State the two products of the fermentation of aqueous glucose by yeast, and explain why the fermenting vessel must exclude oxygen.

   [2 marks]

   Total for question 1: 4 marks

2. 2
   A hospital pharmacy uses ethanol as a solvent to prepare an antiseptic hand rub, and also burns a small sample in a calorimeter to confirm the batch's identity.

   (a)

   Which observation is expected when ethanol undergoes complete combustion?

   [1 mark]

   • AIt produces hydrogen gas and oxygen gas
   • BIt produces only water, absorbing energy
   • CIt produces carbon dioxide and water, releasing energy
   • DIt produces a white precipitate

   (b)

   The pharmacy technician also tests whether the batch has been oxidised, which would spoil it, by adding acidified aqueous potassium manganate(VII). Which product would confirm the ethanol had already been oxidised to a carboxylic acid?

   [1 mark]

   • AEthane
   • BEthene
   • CEthyl ethanoate
   • DEthanoic acid

   (c)

   State two everyday uses of ethanol, based on its properties as a solvent and as a fuel.

   [2 marks]

   Total for question 2: 4 marks

3. 3
   In the early production of vinegar, before industrial methods existed, wine left exposed to air for long periods was observed to turn sour over time, its ethanol content being converted into ethanoic acid. Vinegar producers later found that adding acidified aqueous potassium manganate(VII) directly to wine achieved the same conversion far more quickly.

   (a)

   Explain, in chemical terms, what process was responsible for this change.

   [3 marks]

   (b)

   Compare the two methods described for converting ethanol into ethanoic acid: natural exposure to air over time, and treatment with acidified aqueous potassium manganate(VII). State the type of chemical process common to both, and explain why the potassium manganate(VII) method is more suitable for controlled industrial vinegar production.

   [4 marks]

   Total for question 3: 7 marks

4. 4
   A government energy agency is deciding whether to subsidise ethanol production by fermentation or by the catalytic addition of steam to ethene, in order to increase the supply of biofuel-grade ethanol for the national vehicle fleet.

   (a)

   Explain both methods of producing ethanol, and evaluate the advantages and disadvantages of each in the context of this decision.

   [6 marks]

   (b)

   Once the ethanol biofuel is in widespread use, the agency also wants to understand what happens when it burns in vehicle engines under different conditions. Explain the combustion of ethanol under both complete and incomplete combustion conditions, and discuss the environmental implications of each for a country switching much of its fuel supply to ethanol.

   [6 marks]

   Total for question 4: 12 marks

End of questions