Alcohols

Question 1

What is the general formula for alcohols?

Answer 1

CnH2n+1OH

Question 2

Describe the process of fermentation

Answer 2

Extract sugar
Add yeast
Ferment

Question 3

What are the conditions needed for fermentation?

Answer 3

30-40degrees
CO2 released
Batch process (start + stop)

Question 4

What is the equation for fermentation?

Answer 4

Glucose —-> ethanol + carbon dioxide

Question 5

What is the symbol equation for fermentation?

Answer 5

C6H12O6 (aq) —-> 2CH3CH2OH (aq) + 2CO2 (g)

Question 6

What are the advantages of fermentation?

Answer 6

Sugar = renewable resource
Batch process = cheap
More carbon neutral

Question 7

What are the disadvantages of fermentation?

Answer 7

Very slow
Impure = needs fractional distillation = takes time + money
High labour costs

Question 8

Describe the process of hydration of ethene

Answer 8

Extract crude oil
Fractional distillation then cracking
Hydration

Question 9

What are the conditions needed for the hydration of ethene?

Answer 9

Phosphoric acid catalyst
High temperatures + pressure
Continuous process

Question 10

What is the equation for hydration of ethene?

Answer 10

Ethene + water —-> ethanol

Question 11

What is the symbol equation for hydration of ethene?

Answer 11

C2H4 + H2O —-> CH3CH2OH

Question 12

What are the advantages of hydration of ethene?

Answer 12

Fast
Pure
95% yield
Continuous = cheaper manpower

Question 13

What are the disadvantages of hydration of ethene?

Answer 13

High tech equipment = expensive initially
High energy costs
Non-renewable

Question 14

What are the differences between alcohols and alkanes that have the same no. of carbon atoms?

Answer 14

Less volatile
Higher melting point due to H bonding
Greater water solubility

Question 15

Are methanol and ethanol soluble in water?

Answer 15

YES

Question 16

Why is ethanol and methanol soluble in water?

Answer 16

H bonds form between the OH group of the alcohol and water molecule

Question 17

What happens to solubility as chain length increases?

Answer 17

Solubility decreases since influence of OH group decreases

Question 18

What does classifying alcohols depend on?

Answer 18

No. of H atoms and alkyl groups attached to the carbon atom that contains the alcohol functional group

Question 19

What must a primary alcohol have?

Answer 19

At least 2 H atoms

1 carbon centre

Question 20

What must a secondary alcohol have?

Answer 20

1 H atom

2 carbon centres

Question 21

What must a tertiary alcohol have?

Answer 21

No H atoms

3 carbon centres

Question 22

What happens to the significance of H bonding as chain length increases and what does this mean?

Answer 22

H- bonding significance decreases and London forces increase

This means gap between B.Pts of alcohols and alkanes narrow

Question 23

What does an oxidising agent help something to do?

Answer 23

Gain oxygen or lose electrons

Question 24

What happens to primary alcohols when they are oxidised?

Answer 24

They oxidise to form an aldehyde and water

Question 25

What does the oxidising agent always take off the alcohol?

Answer 25

Takes a H off the alcohol group and a H off the carbon to produce water

Question 26

What is the oxidising agent used in the oxidation of alcohols?

Answer 26

Sodium or potassium dichromate (VI)

Question 27

What is the formula for sodium and potassium dichromate (VI)?

Answer 27

Na2Cr2O7 | K2Cr2O7

Question 28

What must the oxidising agent be in the oxidation of alcohols?

Answer 28

Acidified

Question 29

What does an oxidising agent do?

Answer 29

Helps things to be oxidised so themselves can be reduced

Question 30

What colour does the oxidising agent change from?

Answer 30

Orange to green

Question 31

What happens in the oxidation of an aldehyde?

Answer 31

They oxidise to form a carboxylic acid | The oxygen goes on the H

Question 32

What is further oxidation?

Answer 32

When an alcohol is oxidised twice to form a carboxylic acid

Question 33

What is mild oxidation?

Answer 33

When an alcohol is oxidised once to form an aldehyde

Question 34

What is reflux?

Answer 34

Continuous evaporation + condensation (reactants can't escape the flask)

Question 35

What happens in the oxidation of secondary alcohols?

Answer 35

They oxidise to form ketones

Question 36

What can't happen to ketones?

Answer 36

They can't be oxidised further

Question 37

What happens in the oxidation of secondary alcohols to ensure the reaction is complete?

Answer 37

Alcohol is heated under reflux with oxidising mixture

Question 38

What happens to the dichromate (VI) ions in the oxidation of secondary alcohols?

Answer 38

Changes from orange to green

Question 39

What happens in the oxidation of tertiary alcohols?

Answer 39

Nothing they can't undergo oxidation reactions

Question 40

What happens to the dichromate (VI) ions in the oxidation of tertiary alcohols?

Answer 40

They remain orange