3.2.5 Alcohols

Question 1

What two ways can ethanol be produced?

Answer 1

1. Hydration of ethene
2. Fermentation of glucose

Question 2

What are the positives and negatives of the following methods:
a) Hydration of ethene
b) Glucose fermnetation

Answer 2

a) Continuos process, pure ethanol produced, fast; high energy, non-renewable resources (fossil fuels), expensive

b) Low energy, renewable resources (plant), basic equipment; slow, batch process, impure ethanol

Question 3

Describe the process and conditions of glucose fermentation.

Answer 3

Glucose fermented by yeast:
- anaerobic conditions (no oxygen)
- moisture
- warm temperature (30˚C)

Question 4

Write an equation for the fermentation of glucose.

Answer 4

C6H12O6 → 2CH3CH2OH + 2CO2

Question 5

Describe the process and conditions of the hydration of ethene.

Answer 5

• Phosphoric acid catalyst
• High temperature
• High pressure

Question 6

What is a carbon-neutral process?

Answer 6

No net production of carbon dioxide and emission to the atmosphere

Question 7

What are the following alcohols oxidised to:
a) Primary
b) Secondary
c) Tertiary

Answer 7

a) Aldehyde → carboxylic acid
b) Ketone
c) Difficult to oxidise (only by combustion)

Question 8

How do you oxidise alcohols, what is the colour change?

Answer 8

Acidified potassium dichromate
K2Cr2O7 + H+
orange → green

Question 9

What types of apparatus are used in the following oxidations:
a) 1y alcohol → carboxylic acid
b) 1y alcohol → aldehyde

Answer 9

a) Reflux
d) Distillation

Question 10

Why are anti-bumping granules used in distillation?

Answer 10

• Prevent large bubbles from forming. ensures the liquid doesn’t boil too vigorously
• Stops mixture boiling over into the condenser and undesired impurities contaminating the product

Question 11

Describe the conditions and products for the elimination/dehydration of an alcohol.

Answer 11

Hot, concentrated H2SO4 at 180°C