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A-level
CHEMISTRY
Paper 3

Friday 23 June 2023 Morning Time allowed: 2 hours

Materials
For this paper you must have: For Examiner’s Use
• the Periodic Table/Data Booklet, provided as an insert (enclosed)
• a ruler with millimetre measurements Question Mark
• a scientific calculator, which you are expected to use where appropriate. 1
2
Instructions
3
• Use black ink or black ball-point pen.
• Fill in the boxes at the top of this page. 4
• Answer all questions. 5
• You must answer the questions in the spaces provided. Do not write outside 6
the box around each page or on blank pages.
• If you need extra space for your answer(s), use the lined pages at the end of Section B
this book. Write the question number against your answer(s). TOTAL
• All working must be shown.
• Do all rough work in this book. Cross through any work you do not
want to be marked.

Information
• The marks for questions are shown in brackets.
• The maximum mark for this paper is 90.

Advice
• You are advised to spend 70 minutes on Section A and 50 minutes on Section B.

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Section A box

Answer all questions in this section.

0 1 Ethyl ethanoate can be made by reacting ethanol with ethanoic acid in the presence
of concentrated sulfuric acid.

Method

1. A mixture of ethanol, ethanoic acid, and concentrated sulfuric acid, with

anti-bumping granules, is heated under reflux for 10 minutes.
2. The apparatus is rearranged for distillation.
3. The mixture is heated to collect the liquid that distils between 70 and 85 °C
4. The distillate is placed in a separating funnel. Aqueous sodium carbonate is
added, and a stopper is placed in the funnel. The mixture is shaken, releasing
pressure as necessary.
5. The lower aqueous layer is removed and the upper organic layer is placed in a
small conical flask.
6. Anhydrous calcium chloride is added to the sample in the conical flask. The
flask is shaken well and left for a few minutes.
7. The liquid from the flask is redistilled and the distillate is collected between
74 and 79 °C

0 1 . 1 State the role of concentrated sulfuric acid in this reaction.

[1 mark]

0 1 . 2 The reaction mixture is flammable.

Suggest how the reaction mixture should be heated in step 1.

[1 mark]

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Figure 1 shows how a student set up the apparatus for reflux in step 1.
You should assume that the apparatus is clamped correctly.
Figure 1

Identify two mistakes the student made in setting up the apparatus.

State the problem caused by each mistake.
[4 marks]

Mistake 1

Problem caused

Mistake 2

Problem caused

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0 1 . 4 State why sodium carbonate is added to the distillate in step 4. box

Explain why there is a build-up of pressure in the separating funnel.

[2 marks]

0 1 . 5 Give a reason why two layers form in the separating funnel.

Suggest why ethyl ethanoate forms the upper layer.

[2 marks]

Reason

Suggestion

0 1 . 6 State why anhydrous calcium chloride is added in step 6.

[1 mark]

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0 1 . 7 A student uses the method to prepare some ethyl ethanoate. box

The student adds 10.0 cm3 of ethanol (Mr = 46.0) to 5.25 g of

ethanoic acid (Mr = 60.0) and obtains 5.47 g of ethyl ethanoate (Mr = 88.0).

For ethanol, density = 0.790 g cm–3

Determine the limiting reagent.

Calculate the percentage yield of ethyl ethanoate.

[5 marks]

Limiting reagent

Percentage yield

0 1 . 8 Suggest a reason why the percentage yield is not 100%.

[1 mark]

17

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0 2 This question is about isomerism and the dehydration of alcohols. box

Pentan-2-ol has the molecular formula C5H12O

0 2 . 1 Draw the displayed formula of an unbranched position isomer of pentan-2-ol that can
be dehydrated to form a single alkene.
[1 mark]

0 2 . 2 Draw the skeletal formula of a chain isomer of pentan-2-ol that can be dehydrated to
form a mixture of alkenes.
[1 mark]

0 2 . 3 Draw the structure of an unbranched functional group isomer of pentan-2-ol.

[1 mark]

0 2 . 4 Another isomer of pentan-2-ol is an alcohol that is not dehydrated when heated with
concentrated sulfuric acid.

Draw the structure of this isomer.

[1 mark]

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0 2 . 5 An incomplete mechanism for the dehydration of a compound is shown. box

Complete the mechanism for this reaction by drawing two curly arrows on the
intermediate.

Name the mechanism for this reaction.

[3 marks]

0 2 . 6 An isomer of the final product can also form in the reaction in Question 02.5.

Draw the structure of this isomer.

[1 mark]

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0 3 box
Endomorphin-2 is a peptide with the amino acid sequence shown.

Tyr–Pro–Phe–Phe–NH2

Each amino acid is represented by a three-letter abbreviation.

Tyr = tyrosine Pro = proline Phe = phenylalanine

Figure 2 shows part of the structure of endomorphin-2, showing the Tyr–Pro–Phe–

part of the molecule.

Figure 2

0 3 . 1 The –NH2 at the end of the amino acid sequence of endomorphin-2 shows that the
terminal functional group is an amide, not an acid.

Complete the structure of endomorphin-2 in Figure 2.

[2 marks]

0 3 . 2 Use the structure in Figure 2 to draw the skeletal formula of proline, Pro.
[1 mark]

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A student hydrolyses a sample of endomorphin-2 to break it down into its constituent box

amino acids.

The student analyses the resulting mixture by thin-layer chromatography, TLC.

0 3 . 3 State a reagent and the conditions needed for the hydrolysis.

[2 marks]

Reagent

Conditions

0 3 . 4 Figure 3 shows the apparatus used for the TLC.

Figure 3

There is a piece of the apparatus missing from Figure 3. This omission will result in
an inaccurate chromatogram.

Identify the missing piece of the apparatus.

State and explain why this piece of the apparatus is needed.

[3 marks]

Missing piece

Explanation

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0 3 . 5 State why the amino acids separate on the TLC plate. box

[1 mark]

When the solvent has risen up the TLC plate, the student removes the plate from the
beaker and sprays it with a developing agent.

Figure 4 shows the result.

Figure 4

0 3 . 6 Name a suitable developing agent.

State why the developing agent is needed.

[2 marks]

Name

Why needed

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0 3 . 7 Determine the Rf value for Tyr. box

[1 mark]

12
Rf

Turn over for the next question

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0 4 box
A student is given two aqueous solutions, L and M, that both contain iron salts.

The student does a series of tests on the solutions.

Table 1 shows these tests and the observations.

Table 1

Test Observations with L Observations with M

Add ammonia solution A red-brown precipitate A green precipitate forms
slowly until in excess. forms that is insoluble in that is insoluble in excess.
excess.
Add sodium carbonate A red-brown precipitate A green precipitate forms.
solution. forms.
Effervescence is seen.
Add dilute nitric acid and No change is seen. No change is seen.
then divide into two
portions.

Add barium chloride No change is seen. A white precipitate forms.

solution to the first portion.

Add silver nitrate solution A white precipitate No change is seen.

to the second portion. forms.

Identify L and M using the results in Table 1.

In your answer:
• identify all precipitates
• explain why effervescence is seen in the reaction of sodium carbonate
with L but not with M
• give ionic equations for all reactions.
[6 marks]

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0 5 The molar enthalpy of vaporisation (∆Hvap) of a liquid is the enthalpy change when one box

mole of liquid is converted to vapour at the boiling point of the liquid.

A student does an experiment to determine ∆Hvap for water.

The student:

• places a large beaker on a balance

• pours 500 cm3 of water into the beaker
• uses a 2.4 kW heater to raise the temperature of the water to 100 °C
• records the mass of the beaker and hot water
• uses the 2.4 kW heater to boil the water for 100 s
• records the mass of the beaker and remaining water.

The loss in mass is 103 g

0 5 . 1 Calculate ∆Hvap for water.

[1 kW = 1 kJ s–1]
[3 marks]

∆Hvap kJ mol–1

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Table 2 shows some data about three compounds that all contain the same number box

of electrons.

Table 2

Compound CH3CH2OH CH3CH2NH2 CH3OCH3

Boiling point / K 352 290 248

0 5 . 2 All three compounds in Table 2 are polar.

Ethanol is the most polar and ethylamine is the least polar.

Explain why all three molecules are polar and why ethylamine is the least polar.
In your answer refer to the shapes around, and relative electronegativities of, the most
electronegative atoms.
[4 marks]

0 5 . 3 Explain the trend in the boiling points of the three compounds.

Refer to the intermolecular forces in all three compounds in your answer.
[3 marks]

10

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Calcium hydroxide is almost insoluble in water, but it reacts with
dilute hydrochloric acid.

Ca(OH)2(s) + 2 HCl(aq) → CaCl2(aq) + 2 H2O(l)

A student adds 100 cm3 of 0.100 mol dm–3 hydrochloric acid to

0.600 g of solid calcium hydroxide.

0 6 . 1 Show, by calculation, that the calcium hydroxide is in excess.

[2 marks]

0 6 . 2 The final mixture contains a saturated solution of Ca(OH)2 at 293 K

At 293 K

• the solubility of Ca(OH)2 in this solution is 0.400 g dm–3

• Kw = 6.80 × 10–15 mol2 dm–6

Calculate the pH of this solution.

Give your answer to two decimal places.
[5 marks]

7
pH

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Section B box

Answer all questions in this section.

Only one answer per question is allowed.

For each answer completely fill in the circle alongside the appropriate answer.

CORRECT METHOD WRONG METHODS

If you want to change your answer you must cross out your original answer as shown.

If you wish to return to an answer previously crossed out, ring the answer you now wish to select
as shown.

You may do your working in the blank space around each question but this will not be marked.
Do not use additional sheets for this working.

0 7 Which row shows the number of each fundamental particle in one 25Mg2+ ion?
[1 mark]

protons neutrons electrons

A 12 12 10

B 14 11 12

C 12 13 10

D 12 13 12

0 8 What is the relative molecular mass (Mr) of benzene-1,4-dicarboxylic acid?

[1 mark]

A 164.0

B 166.0

C 168.0

D 170.0

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Which substance has significant electron delocalisation?
[1 mark]

A graphite

B iodine

C sodium chloride

D tetrachloromethane

1 0 Which reaction has a standard enthalpy change equal to the

standard enthalpy of formation for barium chloride?
[1 mark]

A Ba(g) + Cl2(g) → BaCl2(s)

B Ba2+(g) + 2 Cl–(g) → BaCl2(s)

C Ba(s) + Cl2(g) → BaCl2(s)

D Ba2+(s) + 2 Cl–(g) → BaCl2(s)

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1 1 box
This is a Maxwell–Boltzmann distribution for a gaseous reactant.

What is represented by the total area under the curve?

[1 mark]

A total energy of the particles

B activation energy for the reaction

C total number of reacting particles

D total number of particles present

1 2 The rate of reaction is greater when a catalyst is used, without changing the
temperature.

Which statement explains why the rate of reaction is greater with a catalyst?
[1 mark]

A The collision frequency increases because

the catalysed reaction has a lower activation energy.

B The collision frequency increases because

there is an increase in the average energy of the particles.

C The proportion of successful collisions increases because

the catalysed reaction has a lower activation energy.

D The proportion of successful collisions increases because

there is an increase in the average energy of the particles.

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When HF is added to water at 298 K, this equilibrium is established.

HF(aq) ⇌ H+(aq) + F–(aq)

At equilibrium, [HF] = 7.70 × 10–3 mol dm–3 and [F–] = 2.30 × 10–3 mol dm–3

What is the value of the equilibrium constant, in mol dm–3, at 298 K?

[1 mark]

A 1.45 × 103

B 3.35

C 2.99 × 10–1

D 6.87 × 10–4

1 4 In which oxide is the named element in its highest oxidation state?

[1 mark]

A chlorine in ClO2

B magnesium in MgO

C nitrogen in N2O4

D sulfur in SO2

1 5 What happens when water is vaporised?

[1 mark]

A Covalent bonds break within molecules.

B Intermolecular forces are overcome.

C The enthalpy of the molecules decreases.

D The disorder of the molecules decreases.

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Which species can behave as a Brønsted–Lowry acid in aqueous solution?
[1 mark]

A SO42−

B HCO3−

C BF3

D NH3

1 7 Which change causes the pH of 10 cm3 of 1.0 mol dm–3 NaOH to be halved at 298 K?

Kw = 1.0 × 10–14 at 298 K

[1 mark]

A adding 10 cm3 of water

B adding 10 dm3 of water

C adding 5 cm3 of 1.0 mol dm–3 HCl

D adding 10 cm3 of 1.0 mol dm–3 HCl

1 8 A 0.100 mol dm–3 solution of a weak acid has pH = 2.50

What is the value of Ka for this acid, in mol dm–3 ?

[1 mark]

A 3.16 × 10–2

B 3.16 × 10–3

C 1.00 × 10–4

D 1.00 × 10–5

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Which statement is not correct about the Period 3 elements sodium to chlorine?
[1 mark]

A Sodium has the largest atomic radius.

B Sodium has the lowest melting point.

C Silicon has the highest melting point.

D Chlorine has the highest first ionisation energy.

2 0 Equal volumes of pairs of solutions are mixed.

Which pair forms a buffer solution?

[1 mark]

A ammonia and ammonium chloride

B ammonia and methylamine

C ethanoic acid and methanoic acid

D hydrochloric acid and sodium hydroxide

2 1 Barium metal is added to a large excess of water.

Which observation is correct and complete?

[1 mark]

A a colourless solution

B a colourless solution with effervescence

C a dense white precipitate

D a dense white precipitate with effervescence

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Which species is the strongest reducing agent?
[1 mark]

A F2

B I2

C F–

D I–

2 3 Which statement about the shapes of ions is not correct?

[1 mark]

A [CoCl4]2– is square planar.

B NH4+ is tetrahedral.

C [Co(H2NCH2CH2NH2)3]2+ is octahedral.

D [Co(H2O)6]2+ is octahedral.

2 4 Which compound can decolourise acidified potassium manganate(VII) solution?

[1 mark]

A AgNO3

B CuSO4

C FeSO4

D Fe2(SO4)3

Turn over for the next question

Turn over ►

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Which statement about catalysts used in reactions at equilibrium, at a
constant temperature, is correct?
[1 mark]

A They are always used in the solid state.

They increase the rate of the forward reaction but
B
decrease the rate of the reverse reaction.
C They have no effect on the value of the equilibrium constant.

D They make the forward reaction more exothermic.

2 6 Consider this reaction scheme.

Which step is shown with a correct reagent and a correct condition?

[1 mark]

A Step 1 HCN dissolved in water

B Step 2 KOH dissolved in warm water

C Step 4 CH3OH with an alkaline catalyst

D Step 5 H2 with a nickel catalyst

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Which process does not involve a heterogeneous catalyst?
[1 mark]

A catalytic cracking of alkanes

B Contact process

C decomposition of ozone

D Haber process

2 8 The equation for the complete combustion of butane is

1
C4H10 + 6 O2 → 4 CO2 + 5 H2O
2

What is the mole fraction of butane in a mixture of butane and oxygen with the
minimum amount of oxygen needed for complete combustion?
[1 mark]

A 0.133

B 0.153

C 0.167

D 0.200

Turn over for the next question

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Which is not a possible product of a reaction between KOH and ?

[1 mark]

3 0 Most scientists believe that the concentration of ozone in the upper atmosphere
should not be allowed to decrease.

Which statement is a correct reason for this belief?

[1 mark]

A Ozone helps to prevent global warming.

B Ozone is an efficient disinfectant.

C Ozone helps to remove pollutants such as chloroalkanes.

D Ozone absorbs ultraviolet radiation.

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Compound X can be converted into an alcohol in a two-stage process.

What is the name of compound X?

[1 mark]

A propene

B propanal

C methylbenzene

D ethanamide

3 2 Which is a correct equation for the oxidation of 1-phenylethanol?

[O] represents oxygen from an oxidising agent.
[1 mark]

A C6H5CH2CH2OH + 2 [O] → C6H5CH2COOH + H2O

B C6H5CH2CH2OH + [O] → C6H5CH2CHO + H2O

C C6H5CH(OH)CH3 + [O] → C6H5CH2CHO + H2O

D C6H5CH(OH)CH3 + [O] → C6H5COCH3 + H2O

Turn over for the next question

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The skeletal formulas of two compounds are shown.

Which method would distinguish between samples of these compounds?

[1 mark]

A comparing fingerprint regions of their infrared spectra

B obtaining molecular masses from their high resolution mass spectra

C warming with acidified potassium dichromate(VI) solution

D warming with Tollens’ reagent

3 4 Which compound is the strongest base?

[1 mark]

C NH3

D NH4Cl

3 5 Which statement about enzymes is not correct?

[1 mark]

The tertiary structure of an enzyme influences which molecules

A
can bind to the active site.
The action of enzymes can be inhibited by a molecule or ion that
B
binds to the active site.
C Enzymes work equally well on both optical isomers of a substrate.
Computers can be used to design drugs to block active sites on
D
enzymes.

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Cisplatin has the formula [Pt(NH3)2Cl2]
Cisplatin is an anti-cancer drug that prevents replication of DNA.

When cisplatin bonds to DNA, which is the correct ligand replacement reaction?
[1 mark]

A replacement of one NH3 ligand

B replacement of two NH3 ligands

C replacement of one NH3 ligand and one Cl– ligand

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D replacement of two Cl– ligands

END OF QUESTIONS

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DO NOT WRITE ON THIS PAGE

ANSWER IN THE SPACES PROVIDED

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Question Additional page, if required.
number Write the question numbers in the left-hand margin.

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Question Additional page, if required.
number Write the question numbers in the left-hand margin.

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