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Producing ethanol

Edexcel IGCSE Chemistry

Topic questions Organic chemistry Producing ethanol

Producing ethanol

11 questions · 137 marks · about 2.5 hours

Producing ethanol questions

TopicProducing ethanol

Chemistry Paper 2 June 2025 (R), Question 7 15 marks

This question is about ethanol, C₂H₅OH, which can be used as a fuel.

Ethanol can be produced by the fermentation of glucose solution.

(a)

(a)(i)

Name the substance that is added that causes the fermentation of glucose solution.

[1]

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(a)(ii)

Which temperature is most suitable for fermentation?

$Question 7, shown as an image$

[1]

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(a)(iii)

Explain why fermentation is done in the absence of air.

[2]

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(b)

This is the equation for the combustion of ethanol.

$Question 7, shown as an image$

The equation shows the displayed formulae of the reactants and products.

$Question 7, shown as an image$

The table shows some bond energies.

Bond	Bond energy in kJ / mol
C H	414
C C	346
C O	358
O H	463
O O	498
C O	804

(b)(i)

Use the bond energies to show that the molar enthalpy change, Δ H, is about −1300 kJ / mol.

[3]

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(b)(ii)

Complete the energy level diagram for the reaction between C₂H₅OH and O₂

[3]

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(b)(iii)

Explain, in terms of bonds broken and bonds made, why this reaction is exothermic.

[2]

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(c)

Ethanol reacts with compound A to produce ester B and compound C.

This is the equation for the reaction.

H H
H O

$Question 7, shown as an image$

ester B

(c)(i)

Draw the displayed formula for compound A and for compound C.

[2]

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(c)(ii)

Name ester B.

[1]

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Chemistry Paper 2 June 2024 (R), Question 4 8 marks

Also involves Moles and amount of substance

This question is about the manufacture of ethanol by the fermentation of glucose.

(a)

Fermentation needs to be done in the absence of air.

Give two other conditions needed for fermentation.

[2]

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(b)

Explain why fermentation needs to be done in the absence of air.

[2]

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(c)

(c)(i)

Complete the equation for fermentation.

$Question 4, shown as an image$

[1]

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(c)(ii)

A mixture containing 500 mol of glucose is fermented.

A mass of 5750 g of ethanol is obtained.

Calculate the percentage yield.

[for ethanol, M_r = 46]

[3]

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Chemistry Paper 2 June 2024 (R), Question 7 15 marks

Gaseous ethanol is manufactured by reacting ethene gas with steam.

This is the equation for the reaction.

$Question 7, shown as an image$

(a)

(a)(i)

The pressure on an equilibrium mixture of the three gases is decreased. All the other conditions are kept the same.

Predict the effect of this change on the yield of ethanol at equilibrium, giving a reason for your answer.

[2]

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(a)(ii)

Predict the effect of adding a catalyst on the yield of ethanol at equilibrium, giving a reason for your answer.

[2]

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(b)

The equation shows the displayed formulae for the reactants and products.

$Question 7, shown as an image$

The table gives the bond energies.

Bond	Bond energy in kJ / mol
C H	414
C C	614
O H	463
C C	346
C O	358

(b)(i)

Using the data in the table and the equation, show that the enthalpy change, Δ H, is approximately –40 kJ / mol.

[3]

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(b)(ii)

Explain, in terms of bonds broken and bonds made, why this reaction is exothermic.

[2]

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(b)(iii)

Draw an energy level diagram for the reaction between ethene and steam.

Label the enthalpy change, Δ H.

[3]

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(c)

Ethanoic acid reacts with ethanol to form ester A and water.

(c)(i)

Complete the equation by adding the displayed formula of ester A.

$Question 7, shown as an image$

ester A

[2]

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(c)(ii)

Give the name of ester A.

[1]

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Chemistry Paper 2 June 2023, Question 3 15 marks

Also involves Moles and amount of substance

This question is about alcohols.

Ethanol can be manufactured using two different methods.

• hydration of ethene

• fermentation of glucose

This is the equation for hydration.

$Question 3, shown as an image$

(a)

Complete the equation for fermentation.

$Question 3, shown as an image$

[2]

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(b)

The table gives some information about the two methods.

	Hydration	Fermentation
Reagents	ethene and steam	aqueous glucose
Catalyst		enzymes in yeast
Temperature in °C	300
Pressure in atmospheres		1
Rate of process	fast	slow
Purity of product	pure	impure

(b)(i)

Complete the table by giving the missing information.

[3]

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(b)(ii)

Explain one advantage and one disadvantage of using fermentation rather than hydration to produce ethanol.

You should use information from the table to help your answer.

advantage

[4]

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(c)

disadvantage

Explain why fermentation needs to occur in the absence of air.

[2]

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(d)

Propanol has this percentage composition by mass.

C = 60.0% H = 13.3% O = 26.7%

(d)(i)

Show by calculation that the empirical formula of propanol is C₃H₈O.

[3]

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(d)(ii)

Draw the displayed formula of propanol.

[1]

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Chemistry Paper 2 June 2022 (R), Question 5 12 marks

Also involves Moles and amount of substance

This question is about alcohols, carboxylic acids and esters.

(a)

Ethanol can be manufactured by the fermentation of a solution of glucose.

(a)(i)

Write a word equation for this reaction.

[1]

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(a)(ii)

State the substance that needs to be added for the reaction to occur.

[1]

(a)(iii)

State two conditions needed for this reaction.

[2]

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(b)

In the presence of an acid catalyst, ethanoic acid is heated with butanol to form an ester.

(b)(i)

Which of these is the formula of the ester?

$Question 5, shown as an image$

[1]

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(b)(ii)

State how you would know that an ester has formed.

[1]

(b)(iii)

Give one use of an ester.

[1]

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(c)

Aspirin is a compound used to reduce pain.

Aspirin contains a carboxylic acid functional group and an ester functional group.

(c)(i)

State what is meant by the term functional group.

[1]

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(c)(ii)

This is the structural formula of aspirin.

O O

$Question 5, shown as an image$

Draw a circle around the carboxylic acid functional group.

[1]

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(c)(iii)

Aspirin has this percentage composition by mass.

C = 60.00 % H = 4.44 % O = 35.56 %

Show by calculation that the empirical formula of aspirin is C₉H₈O₄

[3]

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Chemistry Paper 2 January 2022, Question 1 7 marks

This question is about the unsaturated hydrocarbon, ethene.

The displayed formula of ethene is

(a)(i)

State the meaning of the term hydrocarbon.

[2]

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(a)(ii)

Give the reason why ethene is described as unsaturated.

[1]

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(b)

Ethene is bubbled through bromine water until there is no further colour change.

Which of these is the appearance of the solution formed?

$Question 1, shown as an image$

[1]

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(c)

Ethanol is produced industrially by the reaction between ethene and steam.

The equation for the reaction is

$Question 1, shown as an image$

(c)(i)

State the temperature and pressure used in this reaction.

temperature

[2]

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(c)(ii)

pressure

Give the molecular formula of ethanol.

[1]

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Chemistry Paper 2 November 2021, Question 6 11 marks

Also involves Amounts of substance in equations · Titrations · Addition polymerisation

This question is about alcohols, carboxylic acids and esters.

(a)

Ethanol can be manufactured by reacting ethene with steam in the presence of a phosphoric acid catalyst.

Which row gives the correct conditions of temperature and pressure for this reaction?

[1]

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(b)

Give the displayed formula of butanol.

[1]

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(c)

Ethanoic acid (CH₃COOH) is a carboxylic acid present in vinegar.

(c)(i)

The concentration of CH₃COOH in vinegar can be found by titration with aqueous potassium hydroxide (KOH).

The equation for the reaction is

CH₃COOH + KOH maths symbol CH₃COOK + H₂O

In a titration, a 25.0 cm³ sample of vinegar is neutralised by 45.00 cm³ of KOH solution of concentration 0.400 mol/dm³.

Calculate the concentration, in mol/dm³, of CH₃COOH in this sample of vinegar.

concentration =_........ mol/dm

[2]

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(c)(ii)

A sample of vinegar containing 0.0030 mol of CH₃COOH is poured into a flask.

Calculate the maximum volume, in cm³, of carbon dioxide gas formed at rtp when excess sodium carbonate is added to the flask.

The equation for the reaction is

$Question 6, shown as an image$

[Assume that the molar volume of carbon dioxide at rtp is 24 000 cm³]

[2]

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(d)

Alcohols react with carboxylic acids to form esters.

Which alcohol could react to form the ester ethyl propanoate?

$Question 6, shown as an image$

[1]

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(e)

Polyesters are formed in condensation polymerisation reactions between dicarboxylic acids and diols.

(e)(i)

State one difference between condensation polymerisation and addition polymerisation.

[1]

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(e)(ii)

The repeat unit of a polyester is

O O H H

$Question 6, shown as an image$

H H

Give the displayed formula of each of the two monomers needed to form this polyester.

[2]

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(e)(iii)

Give one advantage of biopolyesters.

[1]

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Chemistry Paper 2 November 2020, Question 4 15 marks

Also involves Catalysts · Enzymes and drug design

Alcohols contain the functional group —OH

(a)

Give the structural formula of the alcohol that contains one carbon atom.

[1]

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(b)

Ethanol (C₂H₅OH) is an alcohol that can be obtained from glucose (C₆H₁₂O₆).

(b)(i)

Name the process that converts glucose into ethanol.

[1]

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(b)(ii)

Explain why this process is carried out in the absence of air and at a temperature below 40 maths symbol C.

[4]

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(c)

The table gives information about some organic compounds in the same homologous series.

Compound	Molecular formula	Displayed formula
ethanoic acid	C₂H₄O₂
propanoic acid		H H O H C C C H H O H
	C₄H₈O₂	H H H O H C C C C H H H O H

(c)(i)

Complete the table by giving the missing information.

[3]

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(c)(ii)

Name the homologous series that contains these compounds.

[1]

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(d)

The compounds in the table can react with alcohols to form esters.

When preparing esters, a small amount of concentrated sulfuric acid is also used.

(d)(i)

State the purpose of the acid.

[1]

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(d)(ii)

Draw the displayed formula of the ester that forms when propanoic acid reacts with ethanol.

[2]

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(d)(iii)

Esters have particular uses that depend on their properties.

Give an example of a property and use of esters.

[2]

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Chemistry Paper 2 January 2020, Question 6 11 marks

Ethanol, C₂H₅OH, can be manufactured from ethene and steam using a phosphoric acid catalyst.

(a)(i)

State the temperature and pressure used in this manufacturing process.

[2]

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(a)(ii)

Draw the displayed formula of ethanol.

[1]

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(b)

Ethanol burns in a plentiful supply of air to form carbon dioxide and water.

(b)(i)

Give the chemical equation for this reaction.

[2]

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(b)(ii)

When the air supply is limited, incomplete combustion occurs and carbon monoxide forms.

State why carbon monoxide is poisonous to humans.

[1]

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(c)

When ethanol reacts with ethanoic acid, an ester forms.

Give the name of this ester.

[1]

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(d)

Butanedioic acid and ethanediol react together to form a polyester and water.

(d)(i)

Give the name of this type of polymerisation.

[1]

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(d)(ii)

Complete the equation.

Show only one repeat unit of the polyester.

O O

$Question 6, shown as an image$

[3]

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Chemistry Paper 2 January 2020 (R), Question 7 14 marks

Also involves Exothermic and endothermic reactions · Enzymes and drug design

(a) Ethanol, C₂H₅OH, can be produced by the fermentation of glucose, C₆H₁₂O₆

(a)

(a)(i)

Complete the equation for the fermentation of glucose.

$Question 7, shown as an image$

[1]

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(a)(ii)

State why it is necessary for fermentation to be done in the absence of air.

[1]

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(a)(iii)

Explain why the temperature should not be higher than 40 °C.

[2]

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(a)(iv)

When 4 mol of glucose is fermented, a mass of 55.2 g of ethanol is produced.

Show that the percentage yield of ethanol is 15%.

[M_r of C₂H₅OH = 46]

[2]

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(b)

Ethanol can also be produced by the reaction between ethene and steam.

The equation for the reaction is

$Question 7, shown as an image$

(b)(i)

This reaction is in dynamic equilibrium.

Give two features of a reaction in dynamic equilibrium.

[2]

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(b)(ii)

When the equilibrium mixture is heated, the yield of ethanol decreases.

Explain whether the forward reaction is exothermic or endothermic.

[2]

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(c)

Carboxylic acids react with alcohols to form esters.

The displayed formula of an ester is

H H O

$Question 7, shown as an image$

H H H H

(c)(i)

Carboxylic acid A and alcohol B react to produce this ester.

Give the displayed formula of carboxylic acid A and of alcohol B.

[2]

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(c)(ii)

Indicators can be used to test for carboxylic acids.

Describe a different chemical test for a carboxylic acid.

[2]

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Chemistry Paper 2 June 2019, Question 6 14 marks

Some cars in Brazil use ethanol, C₂H₅OH, as a fuel instead of petrol.

The ethanol is made by the fermentation of glucose which is obtained from sugar cane.

The sugar is extracted from the sugar cane and then dissolved in water to make a sugar solution.

(a)(i)

Name the substance that is added to the sugar solution that causes glucose to ferment.

[1]

(a)(ii)

Which temperature is the most suitable for fermentation?

$Question 6, shown as an image$

[1]

Reveal mark scheme

(a)(iii)

Explain why fermentation is done in the absence of air.

[2]

Reveal mark scheme

(b)(i)

State what is meant by the term fuel.

[1]

(b)(ii)

Write a chemical equation for the complete combustion of ethanol in air.

[2]

(c)

Ethanol is also manufactured by reacting steam with ethene, C₂H₄

The equation for this reaction is

$Question 6, shown as an image$

State the conditions of temperature and pressure used in this process.

[2]

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(d)

When ethanol is heated with acidified potassium dichromate(VI), it is oxidised to ethanoic acid.

(d)(i)

State the colour change that occurs in the potassium dichromate(VI) during this reaction.

[1]

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(d)(ii)

The structural formula of ethanoic acid is CH₃COOH

Draw the displayed formula of ethanoic acid.

[2]

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(d)(iii)

Complete the equation for the reaction of ethanoic acid with sodium.

_........CH₃COOH(aq) +_........Na(s) maths symbol _........(aq) +_........(g)

[2]

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