Alcohols (PAPER TWO)

Question 1

What’s the functional group for alcohols?

Answer 1

OH

Question 2

What’s the general formula for alcohols?

Answer 2

CnH2n+1 OH

Question 3

What are the properties of alcohols?

Answer 3

• Flammable (complete combustion in air produces CO2 and H2O)
• Soluble (neutral pH)
• Oxidise to form carboxylic acids (-COOH functional group)
• React with reactive metals

Question 4

What are the uses for alcohols?

Answer 4

Fuels - they release lots of energy when burned (use spirit burner)
Solvents in industry - alcohols can dissolve things that water can’t (e.g. hydrocarbons and lipid compounds)

Question 5

Explain the production of ethanol

Answer 5

• Seeds contain carbohydrate STARCH
• Starch needs to be broken down into sugars
• Seeds are germinated because enzymes in seeds naturally turn starch into sugars
• Plant material containing sugars is mixed with water and yeast
  THEN CARRY OUT FERMENTATION…

Question 6

Explain the process of Fermentation for the production of ethanol

Answer 6

• Glucose produces ethanol and carbon dioxide
• This is done by the enzymes in the yeast, and 30’C temperatures in anaerobic conditions
• Distillation should then be carried out to remove the water (ethanol is in aqueous solution)

Question 7

What are the Pro’s and Con’s of Fermentation?

Answer 7

PRO’S: Low temperatures requires low amounts of energy, sugar used comes from plants which make it renewable
CON’S: Product is aqueous solution of ethanol and water, so we need to purify using distillation which requires energy

Question 8

What are organic molecules?

Answer 8

Organic molecules have a framework of carbon atoms to
which hydrogen and other atoms are attached.

Question 8

What’s the formula for methanol?

Answer 8

CH3OH

Question 9

What’s the word equation for the complete combustion of ethanol?

Answer 9

ethanol + oxygen –> carbon dioxide and water

Question 10

Why does fermentation have to be anaerobic?

Answer 10

The ethanol would react with the oxygen to form a carboxylic acid (vinegar)

Question 11

Name the conditions required to convert ethene into ethanol in industry

Answer 11

(hydration of ethene)
- High temp (200-450)
- High pressure (50-100 atmospheres)
- Reacts with steam
- Catalyst (phosphoric acid)

Question 12

What is a by product of fermentation?

Answer 12

Carbon dioxide

Question 13

What are the benefits and drawbacks of producing alcohol by hydration of ethene over fermentation?

Answer 13

• Produces ethanol only, making it faster and more efficient as there are no waste products formed
• Ethene is cracked from crude oil (non-renewable)
• Requires much more energy = more expensive

Question 14

Explain hydration of ethene to produce ethanol

Answer 14

Ethene reacts with steam.
Double bond breaks open and allows addition of H2O.
Phosphoric acid catalyst.
Produces ethanol only.