3.3.5 Alcohols Flashcards
Industrial production of alcohols - hydration (5)
Hydration of alkenes using steam (reversible)
300°C
60 atm
Solid phosphoric acid catalyst
Low reaction yield (5%) so unreacted ethene gas is recycled
Industrial production of alcohols - fermentation (5)
Fermentation of glucose
30-40°C
Yeast in anaerobic conditions
At 15% alcohol, yeast dies so distillation is used to increase concentration
Purification step takes extra time and money
Hydration of alkenes - advantages (3)
Very fast
Pure product
Low labour costs
Hydration of alkenes - disadvantages (2)
Uses oil - finite resource
Expensive equipment needed
Fermentation of glucose - advantages (2)
Renewable resource - sugars
Cheap equipment
Fermentation of glucose - disadvantages (3)
Very slow
Impure product so needs further processing
High labour costs
What is biofuel?
A fuel made from recently dead biological material
What are the advantages of biofuels? (3)
Renewable energy sources
More sustainable
Considered to be carbon neutral
What are the disadvantages of using biofuels? (3)
Land used for fuel cannot be used to grow food
Deforestation
Fertilisers can pollute waterways
Why is the statement ‘ethanol is a carbon-neutral fuel’ not valid? (5)
When plants are burned the same amount of CO2 is released as they took in in the first place:
Photosynthesis: 6CO2 + 6H2O > C6H12O6 + 6O2
Fermentation: C6H12O6 > 2C2H5OH + 2CO2
Combustion: 2C2H5OH + 6O2 > 4CO2 + 6H2O
However, energy is used by machinery in the processing and transportation of biofuels, releasing more carbon dioxide so ethanol is not carbon neutral
How are aldehydes produced from alcohols? (3)
Primary alcohol oxidised to aldehyde
Heated potassium dichromate and sulphuric acid
Distillation apparatus
How are carboxylic acids produced from alcohols? (3)
Primary alcohol oxidised to carboxylic acid
Potassium dichromate and sulphuric acid
Reflux apparatus
How are ketones produced from alcohols? (3)
Secondary alcohol oxidised to ketone
Acidified potassium dichromate
Reflux
How are tertiary alcohols distinguished from other alcohols? (2)
They are not oxidised when reacted with potassium dichromate
Solution remains orange
How are alkenes formed from alcohols? (2)
Elimination (dehydration)
Heated with conc. sulphuric acid catalyst
