Ethanol

Question 1

Describe and explain the problems associated with producing and using hydrogen and ethanol fuels. (4 marks)

Answer 1

Hydrogen must be manufactured from methane or water. The processes require large amounts of energy and put carbon dioxide into the atmosphere. Storing and transporting hydrogen fuel – an explosive gas – is difficult, dangerous, and expensive.
Ethanol fuel is manufactured from sugar cane or other crops. Although the growing crops remove carbon dioxide from the atmosphere, producing fertilisers and manufacturing ethanol from the plant material both release carbon dioxide to the atmosphere. Some people think that it is unethical to use land to grow fuel instead of food.

Question 2

Ethanol, for use as a fuel, can also be produced from food crops. Evaluate whether more of this ethanol should be produced from food crops or from crude oil. Remember to give a conclusion to your evaluation. (5 marks)

Answer 2

advantages eg:
- renewable (resource) / sustainable
- low / less energy / fuel needed for process or lower temperature
[ignore heat or quoted temperatures]
- can use waste plant / crop material
- carbon neutral
- low safety risk (processes)
- low technology
disadvantages eg:
- batch process / process is slow
- many steps in the process
- ethanol is impure / may contain water
- food shortages
- need very large areas of (arable) land to grow crops or can only grow in certain areas / climates
- destruction of woodland / habitat
- slow growth of crops
- labour intensive
a conclusion with a reasoned argument based on

Question 3

Ethanol can be made using either sugar or alkenes as the starting material. Evaluate the advantages and disadvantages of using these two starting materials to produce ethanol. (4 marks)

Answer 3

Candidates must include both sugar cane and crude oil in their evaluation and both an advantage and a disadvantage to gain full marks. If they do not then the maximum mark is three.
any four from:
advantages of using sugar
• country has no wealth to buy (large quantities of) crude oil
• country has limited technological development
or
underdeveloped / third world country
• able / suitable climate to grow sugar cane
• enough land to grow sugar cane / land cannot be used to grow food / deforestation
• sugar is a renewable source
or
crude oil is a non-renewable resource / finite resource / limited resources
• CO2 / carbon neutral
advantages of using alkenes:
• economic costs are low
• continuous process
• country has large oil resources
• country has oil refineries / cracking plants
• very pure product
• faster process