alcohols

Question 1

what are alcohols?

Answer 1

organic compounds with the hydroxyl functional group

Question 2

what is the general formula of alcohol?

Answer 2

CnH2n+1OH (n>_1)

Question 3

what are the trends down the group?

Answer 3

down the group
the viscosity, flammability and solubility decreases
their melting & boiling point increases

Question 4

What chemical properties do alcohols have / what chemical reactions do alcohols undergo

Answer 4

Combustion -> alcohol + oxygen -> carbon dioxide + water vapour
Oxidation -> alcohol + oxygen from oxidising agent -heat-> carboxylic acid + water

Question 5

What are the two ways ethanol is produced?

Answer 5

From the catalytic addition of steam to ethene

From the fermentation of glucose

Question 6

What are the conditions required for the industrial production of ethanol from ethene?

Answer 6

300*c, 60 atm 
Phosphoric acid (H3PO4) acts as a catalyst

Ethene + steam -> ethanol

Question 7

How can we produce alcohol by fermentation in the laboratory?

Answer 7

Glucose solution - yeast-> ethanol + carbon dioxide
1. A glucose solution is mixed with yeast and the temperature is kept at a temp of about 37*C
2. During fermentation , carbon dioxide is produced and frothing can be observed in the flask , a white precipitate forms in the limewater
3. A dilute solution of ethanol is produced , up to only about 15% concentration as when the alcohol content exceeds this amount the yeast dies and fermentation stops.
Ethanol can be obtained from this liquid mixture by fractional distillation

Question 8

Why can fermentation only take place in the absence of air

Answer 8

In the presence of air bacteria from the air oxidises ethanol to ethanoic acid
The apparatus is secured by ensuring the rubber bung is secured tightly to the flask

Question 9

What are the uses of ethanol?

Answer 9

In alcoholic drinks
As a solvent due to its quick rate of evaporation
Used in paints, deodorant , perfumes etc
As a fuel in cars
For cooking