Alcohols

Question 1

State the disadvantages of hydration of ethene method for making ethanol [3]

Answer 1

High technology equipment needed
Ethene is non-renewable
High energy costs for pumping to produce high pressures

Question 2

State the advantages of the hydration of ethene method for making ethanol

Answer 2

Faster reaction
Purer product
Continuous process (cheaper manpower)

Question 3

State the disadvantages of the fermentation of glucose for making ethanol [3]

Answer 3

Fractional distillation step required for purification
Batch process takes time and money
Depletes land used for growing food crops

Question 4

State the advantages of the fermentation of glucose method for making ethanol [3]

Answer 4

Low-tech
Cheap equipment
Renewable resources only

Question 5

Explain why bromine, a non-polar molecule, is able to react with propene: MS [4]

Answer 5

Double bonds are electron rich and can act as electron pair donors
The bromine becomes polarised and forms an induced dipole
Bromine is an electrophile - a lone pair acceptor
The addition reaction converts the double bond to a single bond

Question 6

Give disadvantages of the use of crops for the production of ethanol: MS [5]

Answer 6

• Growth is subject to the environment
• Reduces land available for food growth
• Requires the use of fossil fuels
• Not carbon neutral
• Requires significant processing after production to separate the ethanol from water

Question 7

Why is the production of bioethanol not carbon neutral, despite the equations saying so?

Answer 7

There is energy used and hence carbon dioxide released from burning of fossil fuels used to
power machinery
the engines of transportation systems
energy used for fractional distillation (fermentation)

Question 8

Why is the optimum temperature for fermentation around 38 degrees?

Answer 8

lower temperatures = too slow
enzyme that convert sugars in ethanol/carobn dioxide is most effective in this range
higher temperatures the yeast die and enzymes denature

Question 9

Why is fermentation done in the abcense of air?

Answer 9

to prevent further extra reactions occuring
can oxidise ethanol to produce ethanoic acid

Question 10

What are the conditions for fermentation?

Answer 10

yeast
no air
temperatures 30-40 degrees celcius

Question 12

Describe the formation of ethanol from ethene
- Reagents:
- Type of Reaction:
- Conditions:

Answer 12

Reagent: Ethene (from cracking of fractions from distilled crude oil)
Reaction: Hydration
Conditions:

Question 13

What are the ways of forming ethanol?

Answer 13

Hydration of ethene
Fermentation