Ethanol

Chapter 3 CC2

The most common use of ethanol in industry is as a solvent

Describe one use of ethanol as a solvent

1 mark

• Ethanol is used as a solvent in antiseptics because it is able to easily dissolve the active ingredient and then readily evaporates from the skin

Relate its solvent properties to the polarity of the ethanol

molecule1 mark

• The C-O and O-H bonds are polar

• This leaves a partial negative charge on the oxygen atom which allows it to easily dissolve polar substances.

Outline TWO uses of ethanol as a fuel

2 marks

• Portable fuel in camping stoves (e.g. methylated spirits)

• Used to modify petrol for use in car engines

Write an equation for the fermentation of glucose

1 mark

Describe conditions under which fermentation is promoted

1 mark

Assess the potential of ethanol as an alternative fuel. In your answer you should assess the impacts and applications of the chemistry you discuss on the

environment and identify possible future directions for research

8 marks

Ethanol as a fuel

• Ethanol is not currently viable as an alternative fuel for mass consumption (1)

• Methods of producing ethanol are expensive compared to obtaining non-renewable supplies such as coal and natural gas. However as supplies of fossil fuels decrease and tax imposed on using fossil fuels increase and/or cheaper alternative methods of producing ethanol are discovered then ethanol may become more competitive (1)

• Ethanol can be produced by fermentation of glucose (greener fuel) (1) however

Advantages:(1) takes glucose from naturally occurring sugar cane and sugar beet. Burning of this fuel has potential to be greenhouse neutral (only CO2 removed from the atmosphere by the plant is returned)

Disadvantages(1)growing of cane occupies large amounts of land therefore clearing of more land. Energy inputs which are greenhouse unfriendly (eg planting, harvesting, burning, distillation). Also wastes from large fermentation plants are difficult to dispose of.

Future research could enhance current technology include (1):

• Improving efficiency of solar powered distillation processes

• Genetic engineering of bacteria to increase the concentration of alcohol produced in fermentation

• Developing mechanisms for the decomposition of cellulose to produce glucose economically.

New technologies might focus on looking on alternative pathways to produce ethanol directly from cellulose

• The most common source of ethanol is from the addition of water to ethylene. (1) However (1)

Disdvantage: ethanol obtained by this method is less efficient than other fuels. Eg petrol produces more energy per gram and costs less to extract.

Advantage: of this method produces a cleaner burn (less soot)