Alcohols, carboxylic acids and esters

Question 1

What are the names and molecular formula of 3 main alkanes?

Answer 1

Methane (CH4), ethane (C2H6) and propane (C3H8)

Question 2

What happens when an alkane burns in plenty of air?

Answer 2

It produces carbon dioxide and water

Question 3

Do alkanes dissolve or react in water? why?

Answer 3

They do not dissolve in water and usually don’t react with aqueous substances, this is because they have single C-C bonds which are hard to break and therefore unreactive

Question 4

What are saturated and unsaturated bonds? how does their presence affect the chemical?

Answer 4

Saturated molecules contain only single bonds between two carbon atoms, they are unreactive,
Unsaturated molecules contain one or more double bond between carbon atoms, they are reactive

Question 5

Which of alkanes and alkenes have unsaturated and saturated molecules?

Answer 5

Alkanes have have saturated molecules while alkenes have unsaturated molecules

Question 6

What is the general formula for alkanes and alkenes?

Answer 6

Alkanes- CnH(2n+2)

Alkenes- CnH(2n)

Question 7

What are the two smallest and most common alcohols? and what is their structural formula?

Answer 7

The smallest alcohol is methanol - CH3OH

The second smallest is ethanol - C2H5OH

Question 8

What is the general formula and functional group for alcohols?

Answer 8

The functional group is -OH

So the general formula is CnH(2n+1)OH

Question 9

What does the presence of the -OH functional group do to the properties of alcohols?

Answer 9

It means unlike alkanes they are all soluble in water, and compared to an alkane with the same number of carbon atoms, they have higher melting and boiling points

Question 10

What the presence of a hydrocarbon chain do to the affect of an alcohol when put under a flame?

Answer 10

It means that the alcohol is flammable and that when burnt they produce carbon dioxide and water

Question 11

How does ethanol react with sodium?

Answer 11

Sodium fizzes as hydrogen gas is made,

It produces hydrogen and for example sodium ethoxide, it reacts because of -OH presence

Question 12

How does fermentation work?

Answer 12

Yeast uses sugar as food to make energy and when it respires anaerobically it produces ethanol and carbon dioxide

Question 13

Why does fermentation stop?

Answer 13

Fermentation can only be used to male dilute ethanol solution as fermentation stops when ethanol becomes more concentrated as higher concentrations kills the yeast that cause fermentation

Question 14

How do we use dilute solutions of ethanol?

Answer 14

Distillation is a process that is used to make ethanol solutions more concentrated, it is used to make fuel and spirits like whisky

Question 15

How does the distillation process work?

Answer 15

Dilute solutions of ethanol are heated to just above ethanol’s boiling point, ethanol boils off leaving water, ethanol vapour cools and condenses to form a liquid

Question 16

How does genetically modified E. coli bacteria convert waste biomass into ethanol?

Answer 16

Plant material from a range of sources is dissolved in acids and solvents, the bacteria use cellulose in plants as food and produce ethanol. Process works at just above room temp.

Question 17

How is ethane from oil converted into ethanol?

Answer 17

Ethane is an alkane in crude oil that can be converted into ethene.
Ethene reacts with steam to produce ethanol, a catalyst is required and distillation separates and purifies the ethanol

Question 18

What are the disadvantages to making ethanol from crude oil and how sustainable is it?

Answer 18

Crude oil is not renewable,

The process requires high temperatures (300*C) which uses lots of energy

Question 19

What are the advantages to making ethanol from crude oil?

Answer 19

It has high atom economy as only hydrogen is made,
hydrogen is an excellent by product as it has many uses,
the process is much faster than fermentation

Question 20

What are the two main carboxylic acids and what are their formula?

Answer 20

Methanoic acid - HCOOH

Ethanoic acid - CH3COOH

Question 21

What is the structural formula for ethanoic acid?

Answer 21

H
     |     = O
H--C--C
      |       \
     H       O -- H

Question 22

What properties do carboxylic acids have?

Answer 22

They have a sharp, unpleasant taste, many have an unpleasant smell

Question 23

What is the functional group of carboxylic acids and what does it do?

Answer 23

-COOH

It gives them their acidic properties

Question 24

How do carboxylic acids react with metals, alkalis and carbonates?

Answer 24

Carboxylic acid + metal = salt + hydrogen
Carboxylic acid + alakli = salt + water
Carboxylic acid + metal carbonate = salt + water
All salts made by carboxylic acids end with ‘-oate’

Question 25

What kind of acids are carboxylic acids?

Answer 25

They are weak acids, they are used to make vinegar and are only corrosive in high concentrations

Question 26

What makes an acid strong or weak?

Answer 26

Strong acids have lower pH than weak acids as they produce a higher concentration of H+ ions when they dissolve in water

Question 27

What happens to acids when dissolved in water?

Answer 27

Strong acids completely ionise in water whereas weak acids do not ionise and most molecules stay as complete molecules

Question 28

How are esters produced?

Answer 28

When carboxylic acids react with alcohols in the presence of a strong acid catalyst

Question 29

What properties do esters have and how are they used as such?

Answer 29

Esters have distinctive smells, often fruity. Natural esters give fruits and flowers their smell. They are also used as food flavourings, solvents and plasticizers, and in perfumes

Question 30

What are the techniques used in making an ester?

Answer 30

Heating under REFLUX,
distillation,
purification using a TAP FUNNEL,
drying

Question 31

How is the name of an ester formed? eg. What does ethanoic acid and methanol produce?

Answer 31

The carboxylic acid gives the first part of the name -thyl and the alcohol gives the second part -anoate.
Ethyl methanoate is produced.

Question 32

What are fats and oils and where do they usually come from?

Answer 32

Fats are solids at room temperature and usually come from animals,
Oils are liquids at room temperature and usually come from plants.
They are esters of glycerol and fatty acids

Question 33

Why do living organisms make fats and oils?

Answer 33

They make them as energy stores

Question 34

What do most animal fats contain?

Answer 34

Most animal fats contain fatty acids with saturated hydrocarbon chains, this means all of the carbon atoms in the chain are joined by single c-c bonds

Question 35

What do most vegetable oils contain?

Answer 35

Most vegetable oils contain fatty acids with unsaturated hydrocarbon chains, this means some of the carbon atoms in the chain are joined by double c=c bonds

Question 36

How can we test for unsaturation?

Answer 36

Bromine water can be used to test, unsaturated compounds turn bromine water from orange-brown to colourless where saturated compounds don’t react, this can be used to test for alkanes and alkenes