The production of ethanol

Question 1

What are the conditions needed to make ethanol with fermentation?

Answer 1

• Yeast
• 35°C
• No air
• Aqueous

Question 2

Why is yeast needed? Give an equation in your answer.

Answer 2

Yeast provides enzymes that catalyse anaerobic respiration (the breakdown of sugar).

C₆H₁₂O₆(aq) -> 2C₂H₅OH(aq) +2CO₂(g)

Question 3

Why is a temperature of 35°C chosen?

Answer 3

The temperature needs to be as high as possible to maximise the rate of reaction but if it is too high then the enzymes in yeast are denatured.

Question 4

Why is air kept out of the fermentation process?

Answer 4

To prevent the oxidation of ethanol to ethanoic acid.

Question 5

When does the fermentation process stop and why?

Answer 5

When the percentage of ethanol reaches 15% as then the enzymes do not work properly.

Question 6

How is ethanol extracted after the fermentation process is complete?

Answer 6

Distillation

Question 7

What are the advantages of the fermentation process over making ethanol from crude oil? (Give two)

Answer 7

• The process can be done with cheap, simple equipment.
• Sugar is a renewable resource

Question 8

What are the disadvantages of the fermentation process over making ethanol from crude oil? (Give three)

Answer 8

• Fermentation is done in a batch process which needs more manpower and is slow
• Ethanol made is not pure
• Depletes land used for growing food crops

Question 9

What is the word equation for fermentation?

Answer 9

glucose -> ethanol + carbon dioxide

Question 10

How is ethene used for the production of ethanol obtained?

Answer 10

The cracking of fractions from crude oil

Question 11

What kind of reaction happens when ethanol is made from ethene? Give an equation.

Answer 11

Addition/hydration

CH₂=CH₂ + H₂O -> CH₃CH₂OH

Question 12

What is the conditions for the hydration of ethene?

Answer 12

• High temperature 300°C
• High pressure 70atm
• H₃PO₄ catalyst

Question 13

What are the advantages of producing ethanol via the hydration of ethene over fermentation? (Give three)

Answer 13

• Faster reaction
• More pure products
• Continuous process

Question 14

What are some disadvantages of producing ethanol via the hydration of ethene over fermentation? (Give three)

Answer 14

• High technology equipment needed
• Ethene is a non-renewable resource
• High energy costs to reach high pressures (70atm)

Question 15

What is the mechanism for the hydration of ethene.

Answer 15