1. 1
   A hand sanitiser manufacturer produces a gel containing ethanol as its main active ingredient, since ethanol is effective at killing many microorganisms on skin. The quality control laboratory tests samples of ethanol and compares its properties with methanol and propanol, two other alcohols used in different products.

   (a)

   A hand sanitiser manufacturer uses ethanol as the main active ingredient in its products because ethanol kills many microorganisms on contact. Ethanol belongs to the alcohol homologous series, whose functional group is:

   [1 mark]

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

   (b)

   The laboratory tests a small sample of ethanol by adding a piece of sodium metal to it. What is observed, and what type of reaction takes place?

   [1 mark]

   • AA white precipitate forms as an insoluble salt is produced
   • BEffervescence (bubbling) as hydrogen gas is produced
   • CNo reaction occurs because alcohols do not react with metals
   • DThe ethanol turns bromine water colourless

   (c)

   The laboratory also burns a small sample of ethanol completely in air and dissolves another sample in water. Describe what is observed or produced in each case.

   [2 marks]

   Total for question 1: 4 marks

2. 2
   A vineyard ferments crushed grape juice using yeast in large sealed vats to produce wine. The winemaker controls the temperature carefully and later distils some of the fermented liquid to produce a more concentrated spirit, which she also tests by adding an oxidising agent.

   (a)

   A vineyard ferments crushed grape juice using yeast to produce wine. During fermentation, sugar from the grapes is converted into ethanol and another gas. Which gas is also produced during fermentation?

   [1 mark]

   • ANitrogen
   • BOxygen
   • CHydrogen
   • DCarbon dioxide

   (b)

   The winemaker keeps the fermentation vats at a temperature of around 25-35 degrees Celsius and seals them to exclude air. Which conditions best describe why fermentation is carried out this way?

   [1 mark]

   • AAn aerobic (oxygen-rich) environment is required for the yeast to produce ethanol
   • BA very high temperature is needed to kill the yeast so it stops respiring
   • CA warm temperature keeps the yeast enzymes active, and anaerobic (oxygen-free) conditions favour ethanol production
   • DA cold temperature and high oxygen levels maximise ethanol yield

   (c)

   The winemaker adds an oxidising agent to a sample of the ethanol produced during fermentation. Describe what happens to the ethanol in this reaction and name the type of product formed.

   [2 marks]

   Total for question 2: 4 marks

3. 3
   A university chemistry course introduces first-year students to the alcohol homologous series, focusing on the first four members: methanol, ethanol, propanol and butanol, and their typical uses in industry and everyday products.

   (a)

   A university chemistry course introduces students to the first four members of the alcohol homologous series: methanol, ethanol, propanol and butanol. State the molecular formula of each of these four alcohols, and identify the common structural feature that places them all in the same homologous series.

   [3 marks]

   (b)

   Methanol is used as a solvent and fuel additive, ethanol is used in alcoholic drinks and as a solvent, propanol is used in cosmetics and hand sanitisers, and butanol is used as a solvent and in some fuel blends. Explain, in terms of molecular structure, why these four alcohols show a gradual change in properties such as boiling point as the series is ascended, and describe how this trend relates to their common industrial uses.

   [4 marks]

   Total for question 3: 7 marks

4. 4
   A rural community that previously relied on imported fuel decides to build a small fermentation and distillation plant to produce ethanol from locally grown sugar crops, intending to use the ethanol as a biofuel for local transport and machinery. The community also makes its own hand-cleaning products.

   (a)

   Explain the process by which the community would produce ethanol from sugar, including the biological agent used, the conditions required, and how a more concentrated ethanol product could then be obtained.

   [6 marks]

   (b)

   Local engineers must decide which alcohol to recommend as the community's fuel and which alcohol to recommend for their existing hand-cleaning products. Explain the typical uses of methanol, ethanol, propanol and butanol, and justify why ethanol is generally the most suitable choice as a locally produced biofuel while another alcohol may be more suitable for hand-cleaning products.

   [6 marks]

   Total for question 4: 12 marks

End of questions