Alcohols Unit 4

Question 1

Define an alcohol

Answer 1

Compounds in which one or more hydrogen atoms in an alkene have been replaced by a hydroxyl Group

Question 2

Why does the boiling point of alcohols increase with increasing chain length

Answer 2

The attractions get stronger as the molecules get longer and have more electrons- increase size of temporary dipoles

Question 3

What is complete oxidation called

Answer 3

Combustion

C2H5OH + O2 –> CO2 + H2O

Question 4

How to oxidise alcohols

Answer 4

Add acidified potassium dichromate

Question 5

What colour changes happens when you oxidise Butan-1-ol

Answer 5

Orange to green

Question 6

Balanced equation for the oxidation of Butan-1-ol to a carboxylic acid

Answer 6

C4H9OH + 2[O] —> C3H7COOH + H2O

Question 7

What conditions are need for the dehydration of an alcohol?

Answer 7

An acid catalyst phosphoric or sulphuric acid

And heat

Question 8

What does the dehydration of an alcohol form

Answer 8

An alkene and a molecule of water

Question 9

Which alcohol reacts the fastest with concentrated hcl

Answer 9

Tertiary

Question 10

What are primary alcohols oxidised to and what does it require?

Answer 10

Aldehydes

Distillation

Question 11

What happens to an aldehyde if heated further with excess acidified potassium dichromate and under reflux?

Answer 11

Carboxylic acid

Question 12

What are secondary alcohols oxidised to and what does it require?

Answer 12

Ketones

Reflux

Question 13

Colour changed of the three types of alcohols

Answer 13

Primary- green
Secondary- green
Tertiary- orange (no change)

Question 14

Why can’t tertiary alcohols be oxidised

Answer 14

They don’t have a hydrogen atom attached to that carbon

Question 15

Physical properties of haloalkanes

Answer 15

Immiscible with water

Boiling point depends on size and number of halogens

Question 16

Define a nucleophile

Answer 16

An electron pair donor

Question 17

What is nucleophillic substitution and what does it require

Answer 17

Hydrolysis reaction that requires aqueous NaOH

Must be under reflux

Question 18

How does the nucleophillic substitution bond break

Answer 18

Heterolytic fission

Question 19

How is heterolytic fission facilitated

Answer 19

By a negatively charged substance reacting with the positively charged carbon atom in a haloalkane

Question 20

Why is dilute nitric acid added to haloalkane with ethanol

Answer 20

Prevents unreacted hydroxide ions reacting with the silver ions

Question 21

Colour of Cl- precipitate

Answer 21

White precipitate

Question 22

Colour of Br- precipitate

Answer 22

Very pale cream precipitate

Question 23

Colour of I- precipitate

Answer 23

Very pale yellow precipitate

Question 24

What happens to the precipitate when ammonia solution is added to AgCl

Answer 24

Precipitate dissolves to give a colourless solution

Question 25

What happens to the precipitate when ammonia solution is added to AgBr

Answer 25

Precipitate is almost unchanged using dilute ammonia solution, but dissolves in concentrated ammonia solution to give a colourless solution

Question 26

What happens to the precipitate when ammonia solution is added to AgI

Answer 26

Precipitate is insoluble in ammonia solution of any concentration

Question 27

Hydrolysis rates of primary, secondary and tertiary alcohols

Answer 27

Tertiary halide produces a precipitate almost instantly The secondary halide gives a slight precipitate after a few seconds. The precipitate thickens up with time The primary halide May take considerably longer to produce a precipitate

Question 28

Reagents and conditions needed to mix 2 alcohols

Answer 28

Acid catalyst Steam High temp

Question 29

Why are some solutions more soluble than others

Answer 29

Weak intermolecular forces OH- Group is polar as is water OH- group can hydrogen bond with water

Question 30

Who concluded that CFCs remain stable until they reach the stratosphere

Answer 30

Rowland and Molina

Question 31

How do CFCs deplete the ozone layer

Answer 31

UV radiation breaks C-Cl bonds by homolytic fission

Question 32

What is it called when radiation initiates the breakdown

Answer 32

Photodissociation

Question 33

What was the global agreement called to protect the ozone layer

Answer 33

Montreal protocol

Question 34

Alternatives to CFCs

Answer 34

Coolants- hydrocarbons, ammonia, CO2 | HCFCs and HFCs

Question 35

in carboxylic acids, how do you count the chain

Answer 35

count from the carbon atom in the -COOH group as being number 1

Question 36

symbol equation for the oxidation of ethanol to ethanoic acid under reflux

Answer 36

CH3CH2OH + [O]--> CH3CHO + H2O CH3CHO + [O] --> CH3COOH CH3CH2OH + 2[O] --> CH3COOH + H2O

Question 37

why is ethanol added to a haloalkane to determine it

Answer 37

it dissolves the haloalkane

Question 38

general equation for radicals affecting the ozone

Answer 38

R. + O3 --> RO. + O2 RO. + O --> R + O2 O3 + O --> 2O2

Question 39

what is ozonolysis

Answer 39

breaks open a C=C bond

Question 40

what is the purpose of adding sodium carbonate solution to the round bottomed flask

Answer 40

neutralises excess acid

Question 41

what is the purpose of adding anhydrous magnesium sulfate

Answer 41

acts as a drying agent