11 mark
Separate: Chemistry Only
Why can esters be used as food flavourings?
| ☐ | A | They are volatile | |
| ☐ | B | They have distinctive colours | |
| ☐ | C | They have fragrant odours | |
| ☐ | D | They are insoluble in water |
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4.7 Esters
21 mark
Separate: Chemistry Only
In a laboratory, ethyl ethanoate can be prepared by heating ethanol, ethanoic acid and sulfuric acid.
The following reaction occurs:
ethanoic acid + ethanol format('truetype')%3Bfont-weight%3Anormal%3Bfont-style%3Anormal%3B%7D%3C%2Fstyle%3E%3C%2Fdefs%3E%3Ctext%20font-family%3D%22math1aa495e18c7e3a21a4e48923b92%22%20font-size%3D%2216%22%20text-anchor%3D%22middle%22%20x%3D%2210.5%22%20y%3D%2216%22%3E%26%23x21CC%3B%3C%2Ftext%3E%3C%2Fsvg%3E)
ethyl ethanoate + water
Which of the following terms cannot be used to describe the reaction that takes place?
| ☐ | A | Esterification | |
| ☐ | B | Condensation | |
| ☐ | C | Reversible | |
| ☐ | D | Thermal decomposition |
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3a2 marks
Separate: Chemistry Only
Ethyl ethanoate belongs to the homologous series, esters.
a)
Complete the structure of ethyl ethanoate.
3b1 mark
Separate: Chemistry Only
Esters can be used in food flavourings.
Give one other use of esters.
3c2 marks
Separate: Chemistry Only
Explain why ethyl ethanoate cannot be referred to as a hydrocarbon.
3d3 marks
Separate: Chemistry Only
Methyl propanoate can be made by a process called esterification.
Use words from the box to complete the sentences about the reaction to produce methyl propanoate.
| methanol | sodium hydroxide | propanoic acid | propanol | |||
| sulfuric acid | methanoic acid | ammonia |
During the esterification process to produce methyl propanoate, the carboxylic acid ...................................... and the alcohol ........................ react together.
The reaction uses concentrated .................................. which acts as a catalyst.
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4a2 marks
Separate: Chemistry Only
Ethyl ethanoate has a distinctive smell which is similar to pear drops.
It is made by the reaction between ethanol and ethanoic acid in the presence of a sulfuric acid catalyst.
i)
State the name that is given to this process.
(1)
ii)
Which of the following is the other product formed during this reaction?
(1)
| ☐ | A | water | |
| ☐ | B | hydrogen chloride | |
| ☐ | C | hydroxide | |
| ☐ | D | hydrogen |
4b
2 marks
2 marksSeparate: Chemistry Only
The displayed formula of ethyl ethanoate is shown below.
Calculate the relative molecular mass of ethyl ethanoate.
(Ar: C = 12, H = 1, O = 16)
4c1 mark
The reaction between ethanoic acid and ethanol to form ethyl ethanoate and another product is a reversible reaction.
Give the sign that is used in reactions to show that a reaction is reversible.
4d1 mark
Separate: Chemistry Only
The reaction between ethanoic acid and ethanol will reach dynamic equilibrium.
Which statement about the dynamic equilibrium of this reaction is correct?
| ☐ | A | the concentration of the reactants equals the concentration of the products | |
| ☐ | B | equilibrium is established in an open container to allow the gases to escape | |
| ☐ | C | the reaction has stopped | |
| ☐ | D | the rate of the forward reaction is equal to the rate of the reverse reaction |
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5a1 mark
Separate: Chemistry Only
Ethyl ethanoate can be prepared in the laboratory using the equipment shown in the diagram below.
Which row in the table correctly identifies X and Y.
| X | Y | |||
| ☐ | A | ethanoic acid and ethanol | ethyl ethanoate | |
| ☐ | B | ethyl ethanoate | ethanoic acid and ethanol | |
| ☐ | C | ethanoic acid, ethanol and sulfuric acid | ethyl ethanoate | |
| ☐ | D | ethyl ethanoate | ethanoic acid, ethanol and sulfuric acid |
5b1 mark
Separate: Chemistry Only
A student carried out a practical to produce ethyl ethanoate using the apparatus shown in part a).
Place a tick (✔) in the box that shows the most suitable method to heat the reaction mixture.
| Bunsen burner | |
| spirit burner | |
| water bath |
5c1 mark
The mixture containing ethyl ethanoate may also contain some acid impurities which can be removed by adding sodium carbonate solution to the mixture.
Give one observation the student would make when sodium carbonate was added to the mixture if acid impurities were present.
5d2 marks
Separate: Chemistry Only
Propyl butanoate is another ester that has a fruity smell is another ester.
Give the name of the carboxylic acid and alcohol that would be required to produce propyl butanoate.
| Carboxylic acid | ............................................................................. |
| Alcohol | ............................................................................. |
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1a4 marks
Separate: Chemistry Only
This question is about esters.
Ester A reacts with water to form ethanoic acid and ethanol.
The displayed formulae of the reactants and products are shown in this equation
The molar enthalpy change (ΔH) for the reaction is 0 kJ / mol.
i)
Draw a ring around the functional group in ester A.
(1)
ii)
Give the name of ester A.
(1)
iii)
Describe a chemical test, other than using an indicator, to show that the reaction mixture contains ethanoic acid.
(2)
1b2 marks
Separate: Chemistry Only
Explain why the molar enthalpy change (ΔH) for the reaction between ester A and water is 0 kJ / mol.
In your answer, refer to the bonds broken and the bonds formed.
1c4 marks
Separate: Chemistry Only
A mixture of ester A and water is left in a sealed container until the reaction mixture reaches dynamic equilibrium.
i)
Describe what is meant by dynamic equilibrium.
(2)
ii)
Explain why adding a catalyst does not change the position of equilibrium.
(2)
1d3 marks
3 marksSeparate: Chemistry Only
The ethanoic acid produced in the reaction is completely neutralised by 22.75 cm3 of 0.150 mol / dm3 barium hydroxide solution.
The equation for the neutralisation reaction is
2CH3COOH + Ba(OH)2 → Ba(CH3COO)2 + 2H2O
Calculate the amount, in moles, of ethanoic acid neutralised.
Give your answer to 3 significant figures.
amount = .............................. mol
1e2 marks
Separate: Chemistry Only
The structures of two organic compounds are shown.
These compounds react together to form a polymer.
Give the repeat unit of the polymer formed.
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2a2 marks
Separate: Chemistry Only
Esters are organic chemicals noted for their characteristic smells. A carboxylic acid and an alcohol will react to form an ester.
Draw the displayed formula of each of the following. Show all the bonds in the structure.
i)
ethanoic acid
(1)
ii)
ethanol
(1)
2b5 marks
Separate: Chemistry Only
Ethanoic acid and ethanol react to form an ester.
i)
What is the name of this ester?
(1)
ii)
The same linkage is found in polyesters. Draw the structure of the polyester which can be formed from the monomers shown below.
HOOC—C6H4—COOH and HO—CH2—CH2—OH
(3)
iii)
Describe the pollution problems caused by non-biodegradable polymers.
(1)
2c3 marks
Separate: Chemistry Only
Ethanoic acid and methanol will react to form a different ester.
i)
Name the catalyst needed to form an ester from ethanoic acid and methanol.
(1)
ii)
Name the ester formed when ethanoic acid reacts with methanol.
(1)
iii)
Give the structural formula of the ester formed when ethanoic acid reacts with methanol.
(1)
2d2 marks
2 marksSeparate: Chemistry Only
The ester methyl butanoate is found in apples. It can be made from butanoic acid and methanol. Their structural formulae are given below.
 |
 |
| butanoic acid | methanol |
Calculate the relative molecular mass of methyl butanoate.
(Ar: C = 12, H = 1, O = 16)
Relative molecular mass .....................................................
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3a3 marks
Separate: Chemistry Only
An ester has the structural formula CH3COOCH2CH2CH3.
i)
Draw out the displayed formula and circle the functional group.
(2)
ii)
State the name of the alcohol used to make this ester.
(1)
3b2 marks
Separate: Chemistry Only
The ester CH3(CH2)2COOCH3 is an ester found in apples and contributes to their smell.
This ester can be prepared in the laboratory from a carboxylic acid and an alcohol.
Write a balanced equation for the production of CH3(CH2)2COOCH3.
3c4 marks
4 marksAn ester, X, was found to contain 39.98% carbon and 6.65% hydrogen.
Show that ester X is not the ester with the formula CH3(CH2)2COOCH3.
3d3 marks
3 marksThe molecular mass of ester X is 60.
Deduce the molecular formula of ester X.
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4a1 mark
Separate: Chemistry Only
A sweet-smelling ester with the empirical formula C2H4O was produced.
Which of the following reactants could not have been used to produce this ester?
| ☐ | A | methanol and propanoic acid | |
| ☐ | B | ethanol and ethanoic acid | |
| ☐ | C | propanol and methanoic acid | |
| ☐ | D | butanol and methanoic acid |
4b2 marks
Separate: Chemistry Only
During the preparation of an ester, the reactants are added to a flask and heated using a water bath.
Explain how and why the ester is separated from the reaction mixture.
4c4 marks
4 marksSeparate: Chemistry Only
A carboxylic acid, Y, was used to form a polyester. The relative formula mass of the carboxylic acid was found to be 90 and its empirical formula is CHO2.
i)
Deduce the molecular formula of carboxylic acid Y.
(2)
ii)
Draw the displayed formula of the carboxylic acid, Y.
(2)
4d1 mark
Separate: Chemistry Only
Carboxylic acid Y reacted with alcohol Z to form a polyester.
Give the formula of the other product in this reaction.
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5a2 marks
Separate: Chemistry Only
An ester was produced in the following reaction between methanoic acid and butanol.
HCOOH + C4H9OH format('truetype')%3Bfont-weight%3Anormal%3Bfont-style%3Anormal%3B%7D%3C%2Fstyle%3E%3C%2Fdefs%3E%3Ctext%20font-family%3D%22math1aa495e18c7e3a21a4e48923b92%22%20font-size%3D%2216%22%20text-anchor%3D%22middle%22%20x%3D%2210.5%22%20y%3D%2216%22%3E%26%23x21CC%3B%3C%2Ftext%3E%3C%2Fsvg%3E)
HCOOC4H9 + H2O
After a period of time, the reaction reaches dynamic equilibrium.
Explain what is meant by the term dynamic equilibrium.
5b2 marks
Separate: Chemistry Only
i)
Give the name of the ester produced during the reaction between methanoic acid and butanol.
(1)
ii)
State the necessary catalyst for the reaction.
(1)
5c5 marks
5 marks4.60 g of methanoic acid was added to 9.62 g of butanol.
Calculate the maximum mass of ester that could be produced from this reaction.
5d2 marks
2 marksThe percentage yield of the reaction was found to be 68.6%.
Determine the mass of ester produced.
Give your answer to 3 significant figures.
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11 mark
Separate: Chemistry Only
Methanoic acid and ethanol react in the presence of an acid to form an ester.
Name the ester that will be formed.
| ☐ | A | Methyl methanoate | |
| ☐ | B | Methyl ethanoate | |
| ☐ | C | Ethyl methanoate | |
| ☐ | D | Ethyl ethanoate |
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2a3 marks
Separate: Chemistry Only
This question is about the reactions of carboxylic acids.
Carboxylic acids react with solutions of metal carbonates.
i)
Complete the chemical equation for the reaction of ethanoic acid, CH3COOH, with potassium carbonate solution.
2CH3COOH + K2CO3 →............................... + ....................... + ........................
(2)
ii)
State what you would see in this reaction.
(1)
2b3 marks
Separate: Chemistry Only
The ester, ethyl ethanoate, can be prepared by reacting ethanol with ethanoic acid.
This is the method for the preparation.
- mix equal amounts of ethanoic acid and ethanol in a boiling tube
- add a few drops of concentrated sulfuric acid
- place the boiling tube in a hot water bath for several minutes
i)
State the role of concentrated sulfuric acid in this reaction.
(1)
ii)
Suggest why the mixture is heated in a water bath rather than directly with a Bunsen burner flame.
(1)
iii)
State how you would know that ethyl ethanoate has formed.
(1)
2c4 marks
Separate: Chemistry Only
Another ester, methyl propanoate, can be prepared by reacting methanol with propanoic acid.
i)
Draw the displayed formulae of methanol, propanoic acid and the ester, methyl propanoate.
(3)
ii)
Give the name of the other product of this reaction.
(1)
2d1 mark
Separate: Chemistry Only
Give one use of esters.
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31 mark
Separate: Chemistry Only
Ethyl ethanoate can be prepared by heating a mixture of ethanoic acid, ethanol and concentrated sulfuric acid.
Which statement about this reaction is not correct?
| ☐ | A | Concentrated sulfuric acid acts as catalyst | |
| ☐ | B | The ester distills first due to its low boiling point | |
| ☐ | C | The mixture is heated using a water bath not a Bunsen burner | |
| ☐ | D | The ethyl ethanoate collected is pure |
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41 mark
Separate: Chemistry Only
Propanoic acid reacts with ethanol in an esterification reaction.
What is the displayed formula of the ester that is formed during this reaction?
| ☐ | A |  |
|
| ☐ | B |  |
|
| ☐ | C |  |
|
| ☐ | D |  |
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5a2 marks
Separate: Chemistry Only
Ethanol, C2H5OH, can be oxidised to produce ethanoic acid, CH3COOH, by heating it with potassium dichromate(VI).
i)
Name one other reactant needed for this reaction to occur.
(1)
ii)
Which colour change occurs during this reaction?
(1)
| ☐ | A | colourless to green | |
| ☐ | B | green to orange | |
| ☐ | C | orange to colourless | |
| ☐ | D | orange to green |
5b5 marks
5 marksSeparate: Chemistry Only
When ethanol is burned in air, complete combustion can occur.
The equation for this reaction is:
C2H5OH + 3O2 → 2CO2 + 3H2O
This equation can also be written using displayed formulae to show all the covalent bonds in the molecules.
The table gives the bond energies for these bonds.
| Bond | C-C | C-H | C-O | O-H | O=O | C=O |
| Bond energy in kJ / mol | 346 | 412 | 358 | 463 | 496 | 743 |
i)
Use values from the table to calculate the energy needed to break all the bonds in the reactants.
(2)
energy needed .............................................................. kJ
ii)
Use values from the table to calculate the energy released when all the bonds in the products are formed.
(2)
energy released .............................................................. kJ
iii)
Calculate the molar enthalpy change (ΔH) in kJ / mol, for the complete combustion of ethanol.
Include a sign in your answer.
Include a sign in your answer.
(1)
ΔH = .............................................................. kJ / mol
5c5 marks
Separate: Chemistry Only
Ethanol reacts with methanoic acid, HCOOH, in the presence of an acid catalyst to form an ester.
The equation for the reaction is:
C2H5OH + HCOOH HCOOC2H5 + H2O
HCOOC2H5 + H2Oi)
Give the name of the ester that forms.
(1)
ii)
Draw the displayed formula for this ester.
(2)
iii)
When this reaction takes place in a sealed container, the reaction can reach dynamic equilibrium.
Give two characteristics of a reaction at dynamic equilibrium.
(2)
5d4 marks
4 marksSeparate: Chemistry Only
Methanoic acid reacts with sodium carbonate to form sodium methanoate, carbon dioxide and water.
The equation for the reaction is:
2HCOOH + Na2CO3 → 2HCOONa + CO2 + H2O
Calculate the volume, in cm3 , of carbon dioxide gas produced when 2.3 g of methanoic acid reacts completely with sodium carbonate.
[Mr of HCOOH = 46]
[Molar volume of carbon dioxide at rtp = 24 dm3]
volume of carbon dioxide = .............................................................. cm3
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