11. Alcohols

Question 1

Advantages of Direct Hydration

Answer 1

• high purity ethanol made
• continuous production method
• fast (high rate of reaction)

Question 2

Disadvantages of Direct Hydration

Answer 2

• crude oil = non renewable
• high pressure + temp = expensive as needs lots of energy
• high tech equpment needed = expensive

Question 3

Photosynthesis Equation:

Answer 3

6CO2 + 6H2O -> C6H12O6 + 6O2

Question 4

Fermentation Equation

Answer 4

C6H12O6 -> 2CH3CH2OH + 2CO2

Question 5

Combustion Equation

Answer 5

2CH3CH2OH + 6O2 -> 4CO2 + 2H2O

Question 6

why isn’t bio-ethanol considered carbon neutral?

Answer 6

processes in production/distribution of bioethanol require fossil fuels that release CO2 e.g: harvesting, transport, extracting

Question 7

Advantages of fermentation

Answer 7

• uses renewable resource (glucose)
• lower temp = less energy = low cost
• low tech equpment = cheaper

Question 8

Disadvantages of fermentation:

Answer 8

• land used to grow crops isn’t vailable for food production
• impure ethanol made needs distilling
• low yield
• slow rate of reaction

Question 9

Feature + purpose of condenser

Answer 9

Features:
- open at both ends
- cold water flows around outside

Purpose:
- cools hot vapour + condenses back into liquid

Question 10

purpose of antibumoing granules

Answer 10

prevents formation of larger bubbles

Question 11

Reflux Steps

Answer 11

1. aldehyde vapour rises + enters condenser
2. aldehyde vapour cools and condenses and drops back into reaction mixture

Question 12

Why is reflux used to oxidise primary alcohol to carboxylic acid?

Answer 12

doesn’t allow any remaining reactant vapour to escape

Question 13

Describe what happens when reaction mixture is refluxed and why it’s necessary to complete oxidation for a carboxylic acid

Answer 13

• ethanol + acidified K2Cr2O7 are heated to bpt for prolonged period of time
• ethanal vapour is formed which escapes from liquid reaction mixture and is then condensed back into liquid and returned to reaction mixture

Question 14

why is distillation used when forming an aldehyde from a primary alcohol?

Answer 14

allows aldehyde vapour to escape reaction mixture and prevent further oxidation

Question 15

ethanol can be oxidised to ethanal or ethanoic acid. describe how ethanal can be made in high yield as opposed to ethanoic acid

Answer 15

• use distillation
• heat at bpt of ethanal
• collect ethanal as its distilled off