Alcohols

Question 1

State 3 essential conditions for the conversion of glucose into ethanol. Justify these conditions

Answer 1

-yeast
Speeds up rate of reaction, so contributes to low cost

-anaerobic / absence of oxygen/air

Temperature range from 30-40 degrees Celsius
Optimum temp for enzyme to work
Too high = enzyme denatures
Too low = reaction rate too slow

Question 2

Equation for fermentation

Answer 2

C6H12O6 —> 2CH3CH2OH + 2CO2

Question 3

What is dehydration?

Answer 3

Elimination of water from a compound

Question 4

Conditions for dehydration of ethanol

Answer 4

Concentrated H2SO4 or concentrated H3PO4 as a catalyst
High temps around 300 degrees Celsius

Question 5

Equation for acid-catalysed dehydration of ethanol

Answer 5

CH3CH2OH —> H2C=CH2 + H2O

Question 6

Test to distinguish between 2-methylpropan-2-ol and butan-1-ol

Answer 6

acidified potassium dichromate (VI) solution
-butan-1-ol turns it from orange to green
-no visible change for tertiary alcohols

Question 7

Advantage of using ethanol as a fuel compared with using a petroleum fraction

Answer 7

sugar/glucose/ethanol is renewable
OR
ethanol does not contain sulfur-containing impurities
OR
ethanol produces less pollution / is less smoky / less CO/C

Question 8

Define biofuel

Answer 8

Fuels made from plants, hence renewable

Question 9

Why is fermentation of sugars considered carbon-neutral?

Answer 9

6CO2 + 6H2O -> C6H12O6 (photosynthesis)

C6H12O6 -> 2C2H5OH +2CO2 (fermentation)

2C2H5OH + 6O2 -> 4CO2 + 6H2O (combustion)

Question 10

What does carbon-neutral mean?

Answer 10

If the production and use of the fuel has no net effect on the amount of carbon dioxide in the atmosphere