Alcohols

Question 1

What is the equation for a dehydration reaction

Answer 1

Alcohol —> Alkene + water

Question 2

What is used as a catalyst in the alcohol dehydration reaction

Answer 2

Concentrated H2SO4 and concentrated H3PO4

Question 3

Describe ethanol production via hydration of ethene

Answer 3

React an alkene with steam and an acid catalyst

Question 4

What are the conditions for ethanol production via hydration of ethene

Answer 4

300 degrees Celsius, 60 atm, H3PO4 catalyst

Question 5

Why isnt ethanol production by hydration of ethene preferable

Answer 5

• ethene is a finite resource
• drilling for crude oil is an expensive process and damages the environment

Question 6

How else can ethanol be produced

Answer 6

Fermentation of glucose

Question 7

Is the reaction of fermentation of glucose a exo or endothermic reaction

Answer 7

Exothermic reaction

Question 8

Give 3 conditions for the fermentation of glucose

Answer 8

• yeast
• anaerobic
• 30 - 40 degrees Celsius

Question 9

Why is ethanol production by fermentation of glucose preferable

Answer 9

Uses cheap equipment and renewable resources

Question 10

Give the overall equation for fermentation of glucose

Answer 10

C6 H12 O6 —> 2 C2 H5 OH + 2 CO2

Question 11

How is ethanol separated in the fermentation of glucose

Answer 11

Via fractional distillation

Question 12

Define a biofuel

Answer 12

A fuel which is made from dead organic matter

Question 13

Give an example of a biofuel

Answer 13

Ethanol when made from fermentation of glucose

Question 14

Give 2 advantaged of biofuels

Answer 14

• they’re renewable energy sources
• they’re carbon neutral

Question 15

Why are biofuels carbon neutral

Answer 15

CO2 released when burnt = CO2 absorbed during photosynthesis

Question 16

Give 2 disadvantages of biofuels

Answer 16

• cars must be modified to use ethanol fuel
• land needed to grow crops

Question 17

Why isn’t ethanol production by fermentation of glucose completely carbon neutral

Answer 17

Fuels burnt to transport crops, and power machines for fertilisers

Question 18

Give the equation for photosynthesis

Answer 18

6CO2 + 6H2O —> C6 H12 O6 + 6O2

Question 19

Give the equation for burning ethanol

Answer 19

2 C2 H5 OH + 5O2 —> 4CO2 + 6H2O

Question 20

What oxidising agent is used to oxidise and alcohol

Answer 20

Acidified potassium dichromate

Question 21

What is observed when an alcohol is oxidised

Answer 21

Orange Cr2 O7 - reduces to green Cr3+

Question 22

How do you acidify potassium dichromate solution

Answer 22

Add dilute sulfuric acid

Question 23

What do primary alcohols oxidise to

Answer 23

Distillation: oxidise to aldehydes
Reflux: oxidise to carboxylic acids

Question 24

What do secondary alcohols oxidise to

Answer 24

Ketones under reflux

Question 25

What conditions are needed to oxidise a primary alcohol to an aldehyde

Answer 25

Limited amount of dichromate. Warm gently with distillation

Question 26

What conditions are needed to oxidise a primary alcohol to a carboxylic acid

Answer 26

Excess of dichromate, heat under reflux

Question 27

What do tertiary alcohols oxidise to

Answer 27

They don’t oxidise

Question 28

Why is fermentation done in the absence of air

Answer 28

Presence of air can cause extra reactions to occur, like the oxidation of ethanol to ethanoic acid

Question 29

Give 3 disadvantages of producing ethanol by fermentation

Answer 29

- slow batch process of high production costs - not pure ethanol produces=d, so has to be purified by fractional distillation - depletes land used for growing crops

Question 30

Give 3 advantages of producing ethanol by hydration of ethene

Answer 30

- faster reaction - continuous process - purer product

Question 31

Give 3 disadvantages of producing ethanol by hydration of ethene

Answer 31

- High technology equipment needed - Ethene is non renewable - High energy costs for pumping to produce high pressures