3.3.5 - Alcohols

Question 1

General formula of alcohols

Answer 1

CnH2n+1OH

Question 2

Hydration

Answer 2

Produces alcohols from alkenes in the presence of an acid catalyst. Phosphoric acid is commonly used as the catalyst under aqueous conditions at 300c and high pressures

Question 3

Percentage yield of hydration

Answer 3

very high as ethanol is the only product so the hydration method is favoured as an industrial process

Question 4

Fermentation

Answer 4

Enzymes break down starch from crops into sugars which can then be fermented to form alcohol. This method is cheaper than hydration as it can be carried out at a lower temperature

Question 5

Percentage yield of fermentation

Answer 5

Much lower than hydration, and it is a much slower process as it has to be fermented in batches

Question 6

Ethanol

Answer 6

Common biofuel produced by fermentation. It is said to be carbon neutral as the carbon given out when it is burned is equal to the carbon taken in by the crops during the growing process

Question 7

1 ° alcohols can be heated in the presence of…

Answer 7

Acidified potassium dichromate and distilled to produce aldehydes. When heated further under reflux conditions, they oxidise further to produce carboxylic acids

Question 8

2 ° can be oxidised when heated in the presence of…

Answer 8

acidified potassium dichromate to produce ketones

Question 9

Potassium dichromate

Answer 9

Used in the oxidation of alcohols as the oxidising agent. It is reduced as the alcohol is oxidised. This can be observed as a colour change from orange to green when the alcohol is oxidised

Question 10

Dehydration of alcohols

Answer 10

Alkenes can be formed, where a molecule of water is removed from the alcohol

Question 11

Alkenes to alcohols in the presence of an acid catalyst

Answer 11

Hydration

Question 12

Reaction conditions for dehydration of alcohols

Answer 12

Excess hot sulfuric acid and an aluminium oxide catalyst