Alcohol Production

Question 1

What are the two methods of alcohol production?

Answer 1

Hydration and fermentation

Question 2

What is the general formula for alcohols?

Answer 2

CnH2n+1OH

Question 3

What is an equation for hydration?

Answer 3

CH2=CH2 (g) + H2O (g) -> CH3CH2OH (l)

Ethene + Steam -> Ethanol

Question 4

What catalyst is often used in hydration and under what conditions?

Answer 4

Concentrated phosphoric acid
Conditions:
- aqueous
- 300C
- pressure of 70 atm
- Excess steam

Question 5

Define hydration

Answer 5

The addition of water to a molecule

Question 6

Advantages of hydration?

Answer 6

Faster reaction
Purer product (only product so high % yield)
Continuous process (cheaper manpower)

Question 7

Disadvantages of hydration?

Answer 7

High tech equipment needed (expensive initial costs)
Ethene is non-renewable
High energy costs for pumping to produce high temperatures

Question 8

What is the equation for fermentation?

Answer 8

C6H12O6 -> 2 CH3CH2OH + 2 CO2

Glucose -> ethanol + carbon dioxide

Question 9

What conditions are needed in fermentation and give a reason for each

Answer 9

Yeast
No air - because otherwise extra reactions can have, oxidising the ethanol produced to ethanoic acid (vinegar)
30 - 40 (38 optimum) - at low temps, the reaction is too slow, and at higher temps, the yeast dies and the enzymes denature

Question 10

Advantages of fermentation?

Answer 10

Sugar is renewable
Production uses low level technology/cheap equipment

Question 11

Disadvantages of fermentation?

Answer 11

Batch process which is slow and gives high production costs
Small % yield
Ethanol made is not pure and needs purifying by fractional distillation
Depletes land used for growing food crops

Question 12

What is ethanol produced by fermentation often used for?

Answer 12

A biofuel

Question 13

What is a biofuel

Answer 13

A fuel produced by plants

Question 14

Write a sentence to support the statement that ethanol produced by biofuel is a carbon neutral fuel

Answer 14

Any carbon dioxide given off when the biofuel is burnt would have been extracted from the air by photosynthesis when the plant grew.

Question 15

Balanced photosynthesis equation and then for fermentation + combustion

Write equations to support the statement that ethanol produced by biofuel is a carbon neutral fuel

Answer 15

Production of CO2 by photosynthesis:
6 CO2 + 6 H2O -> C6H12O6 + 6 O2
6 CO2 molecules removed from the atmosphere to make 1 glucose molecule

Production of CO2 by ferm. and combustion:
C6H12O6 -> 2 CH3CH2OH + 2 CO2
2 CH3CH2OH + 6O2 -> 4 CO2 + 6 H2O
1 glucose ferm. causes 2 CO2 molecules to release
2 ethanol molecules produce 4 CO2.

Absorbed CO2 = Emitted CO2

Question 16

Why might the statement that ethanol from fermentation is a biofuel be not valid?

Answer 16

Because this does not take into account any energy needed to irrigate plants, fractionally distil the ethanol or process the fuel. If the energy for these processes comes from fossil fuels, then the ethanol produced is not carbon neutral.

Question 17

What does carbon neutral mean?

Answer 17

An activity that has no net annual carbon (greenhouse gas) emissions to the atmosphere

Question 18

Environmental and ethical issues about biofuels

Answer 18

Land and water resource requirements, air and ground water pollution.
Food security and prices, and on the human rights of workers and communities in countries where biofuels crops are grown.