Alcohol and carboxylic acids

Question 1

Alcohols

Answer 1

Homologous series containing - OH as functional group

Question 2

Primary alcohol

Answer 2

OH join to a carbon and 2 other hydrogens

Question 3

Secondary alcohol

Answer 3

O H Group is joined to a 2 alkyl groups and hydrogen

Question 4

Tertiary alcohol

Answer 4

Join to three carbons and no hydrogens

Question 5

Hydration of ethene

Answer 5

Obtained by cracking hydrocarbons produced from petroleum, react with steam to produce ethanol
CH2=CH2(g) + H2O(g) —> CH3CH2OH (g)

Question 6

Le Chateliars principle

Answer 6

States that if a system at equilibrium is subjected to a change, the equilibrium tends to shift so as to minimise the effect of the change

Question 7

Temperature in hydration of ethene

Answer 7

Since the forward reaction is exothermic, a high yield will be favoured by a low temperature., however, gives a slow rate of reaction: 300 degrees is a comprise temperature

Question 8

Pressure and hydration of ethene

Answer 8

In the reaction, two moles of gas reactor produce 1 mole of gas. A high yield is therefore favoured by a high pressure
high pressure also increases the rates of reaction
60-70 atm

Question 9

Reasons high pressure isn’t used

Answer 9

if pressure is too high more powerful pumps and stronger pipes are needed and this increases costs
At high pressure ethene polynerisis into polyethene and this wastes ethene and clogs up the plant

Question 10

catalyst in hydration of ethene

Answer 10

Catalyst does not affect the yield but it does increase the rate in which ethene and steam react to produce the equilibrium concentration of ethanol
Catalyst of phosphoric acid coated onto a inert solid

Question 11

Inert solid

Answer 11

Doesn’t react with anything so the solid won’t react and change the reaction

Question 12

Fermentation of etheme

Answer 12

Enzyme catalysted reaction that converts sugars to ethanol
eg glucose: C6H12O6 —> 2C2H5OH + 2CO2

Question 13

Fractional distillation needed in fermentation

Answer 13

Carbon dioxide escapes as a gas but ethanol has to be separated from the remaining liquid mixture. Temperature of ethanol is seventy eight degrees and therefore to separate it from an aqueous mixture fractional distillation is needed

Question 14

Biofuel

Answer 14

Fuel that has been produced using a biological source

Question 15

Advantages of biofuel - renewable

Answer 15

Fossil fuels are non-renewable and will eventually run out. Can be grown each year and biofuels can also be produced using waste material from animals

Question 16

Advantages of biofuels - greenhouse gases

Answer 16

Production of carbon dioxide is reduced
Carbon dioxide is taken in by plants when they are grown and used for photosynthesis to produce sugars
Carbon dioxide is produced in one process but removed in another so use of biofuels is carbon neutral

Question 17

Carbon neutral

Answer 17

Process where there is no net transfer of carbon dioxide to or from atmosphere

Question 18

Advantages of biofuels - economic and political security

Answer 18

Countries that are able to grow crops like sugar cane and create own biofuels do not need to use fossil fuels
Countries producing biofuels are less affected by changes in fossil fuel prices and changes in availability

Question 19

Disadvantages of biofuels - land use

Answer 19

land Used to produce plants for biofuels cannot be used to produce food, there is also pressure to destroy environmentally significant areas like forests to create land for biofuel production

Question 20

Disadvantages of biofuels- use of resources

Answer 20

Growing crop suitable for biofuels in these large quantities of water and fertilisers. use of Water can strain local resources and use of large quantities of fertilisers to grow the same crop year after year can cause water pollution

Question 21

Disadvantages of biofuels - carbon neutrality

Answer 21

When the fuel needed to build and run the factories for biofuel production, to transport raw materials and finished products is considered
It can be argued that the use of such fuels is not carbon neutral

Question 22

Oxidation of alcohols

Answer 22

Acidified potassium dichromate can be used to oxidise many alcohols
The dichromate will only behave satisfaction as an oxidising agent to the presence of H+
Carried out by heating alcohol with a mixture of aqueous potassium dichromate and sulfuric acid

Question 23

Oxidation of primary alcohols

Answer 23

Two stages
Eg. Ethanol + [O] –> Ethanal + H2O
Stage1:
Two hydrogen atoms are lost - one from the alcohol O H and one from the adjacent carbon creating carbon to oxygen double bond
Stage 2:
Ethanal + [O] –> Ethanoic acid
Oxygen is added to the aldehyde

Question 24

Oxidation of secondary alcohols

Answer 24

Eg. Propan-2-ol
One stage,
Propan-2-ol + [O] –> propanone + H2O
Ketone

Question 25

Oxidation of tertiary alcohols

Answer 25

Eg. 2- methylpropa-2-ol
There is no hydrogen on an adjacent carbon that can be lost so no reaction takes place

Question 26

Colour change of acidified potassium dichromate

Answer 26

Changes from orange to green
Test for primary and secondary alcohol since they will give positive test results for tertiary alcohols will not

Question 27

Structure of carboxylic acids

Answer 27

R-C=O
-O-H
Acidic because they release H ions when added to water
weak acid so when it dissolves in water only a small percentage of H ions are formed

Question 28

Reactions of carboxylic acids- as an acid reacts to bases

Answer 28

Both soluble bases like alkali’s and solid bases like metal oxides neutralised carboxylic acids
Acid + base = salt + water
( alkali NaOH) All reagents and products are colourless and solid boiling water so no visible change occurs
( CuO) when warm the black solid copper oxide dissolves the form blue solution of as salt

Question 29

Reactions of carboxylic acids carbonates and hydrocarbonates

Answer 29

both react in similar ways
Acid + carbonate = salt + CO2 + H2O
Co2 is always produced, therefore an effveressence is seen and a gas can be shown testing w limewater

Question 30

Reactions of carboxylic acids Esterification

Answer 30

react w alcohols
Carboxylic acid + alcohol –> ester + water
Reaction is catalysed by presence of concentrated sulfuric acid
esther produced has charactistic sweet fruity odor

Question 31

Practical activity - ester

Answer 31

Carboxylic acid alcohol and concentrated sulfuric acid are heated together in a flask producing equilibrium mixture of Esther with some carboxylic and alcohol. Esther removed by distillation

Question 32

Dehydration of alcohol

Answer 32

Dehydrated to form alkanes + H2O
Concentrated sulfuric acid or heated aluminium oxide commonly used
Reaction is the elimination since double bond is produced by removal of O H from one carbon and one H from adjacent carbon atom