ccea gce specimen assessment material for chemistry · 2019-09-19 · for first teaching from...

For first teaching from September 2016For first award of AS level in Summer 2017For first award of A level in Summer 2018Subject Code: 1110

CCEA GCE SpecimenAssessment Material for

Chemistry

GCE

Version 2: Update 12 October 2016

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GCE_CHEM_SAM_V.2 UPDATED_12.10.16

ForewordCCEA has developed new specifications which comply with criteria for GCE qualifications. The specimen assessment materials accompanying new specifications are provided to give centres guidance on the structure and character of the planned assessments in advance of the first assessment. It is intended that the specimen assessment materials contained in this booklet will help teachers and students to understand, as fully as possible, the markers’ expectations of candidates’ responses to the types of tasks and questions set at GCE level. These specimen assessment materials should be used in conjunction with CCEA’s GCE Chemistry specification.


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GCE ChemistrySpecimen Assessment Materials

Contents

Specimen Papers 3

Assessment Unit AS 1: Basic Concepts in Physical and Inorganic Chemistry 3

Assessment Unit AS 2: Further Physical and Inorganic Chemistry and an Introduction to Organic Chemistry

25

Assessment Unit AS 3: Basic Practical Chemistry – Practical Booklet A 45

Assessment Unit AS 3: Basic Practical Chemistry – Practical Booklet B 53Assessment Unit A2 1: Further Physical and Organic Chemistry 65Assessment Unit A2 2: Analytical, Transition Metals, Electrochemistry and

Organic Nitrogen Chemistry89

Assessment Unit A2 3: Further Practical Chemistry – Practical Booklet A 113Assessment Unit A2 3: Further Practical Chemistry – Practical Booklet B 123

Apparatus and Materials Lists 135

Assessment Unit AS 3: Basic Practical Chemistry – Practical Booklet A 137Assessment Unit A2 3: Further Practical Chemistry – Practical Booklet A 145

Mark Schemes 155

General Marking Instructions 157Assessment Unit AS 1: Basic Concepts in Physical and Inorganic Chemistry 161Assessment Unit AS 2: Further Physical and Inorganic Chemistry and an

Introduction to Organic Chemistry167

Assessment Unit AS 3: Basic Practical Chemistry – Practical Booklet A 175Assessment Unit AS 3: Basic Practical Chemistry – Practical Booklet B 177Assessment Unit A2 1: Further Physical and Organic Chemistry 181Assessment Unit A2 2: Analytical, Transition Metals, Electrochemistry and

Organic Nitrogen Chemistry189

Assessment Unit A2 3: Further Practical Chemistry – Practical Booklet A 195Assessment Unit A2 3: Further Practical Chemistry – Practical Booklet B 199


Subject Code 1110

QAN ASQAN A2

601/8511/9601/8512/0

A CCEA Publication © 2016

You may download further copies of this publication from www.ccea.org.uk GCE_CHEM_SAM_V.2 UPDATED_12.10.16

SPECIMEN PAPERS

DIVIDER FRONT


SPECIMEN PAPERS

DIVIDER BACK


TIME1 hour 30 minutes.

INSTRUCTIONS TO CANDIDATESWrite your Centre Number and Candidate Number in the spaces provided at the top of this page.Write your answers in the spaces provided in this question paper.Answer all sixteen questions.

INFORMATION FOR CANDIDATESThe total mark for this paper is 90.Figures in brackets printed down the right-hand side of pages indicate the marks awarded to each question or part question.Quality of written communication will be assessed in Question 16(b)(i)A Data Leaflet including a Periodic Table of the Elements is included with this question paper.

For Examiner’suse only

Question Number Marks

Section A 1–10

Section B 111213141516

TotalMarks

Chemistry

Assessment Unit AS 1

Basic Concepts in Physical and Inorganic Chemistry

[CODE]SPECIMEN PAPER

Centre Number

Candidate Number

ADVANCED SUBSIDIARY (AS)General Certificate of Education

2017

3GCE_CHEM_SAM_V.2 UPDATED_12.10.16

4

[227]

89

139

57

[256]

101

[223]

87

[226]

88

[261]

104

[262]

105

[266]

106

[264]

107

[277]

108

[268]

109

[271]

110

[272]

111

140

58

141

59

144

60

145

61

150

62

152

63

157

64

159

65

162

66

165

67

167

68

169

69

173

70

175

71232

90

[231]

91

238

92

[237]

93

[242]

94

[243]

95

[247]

96

[245]

97

[251]

98

[254]

99

[253]

100

[254]

102

[257]

103

133

55

137

56

178

72

181

73

184

74

186

75

190

76

192

77

195

78

197

79

201

80

89

39

91

40

103

45

85

37

88

38

93

41

96

42

[98]

43

101

44

106

46

108

47

112

48

131

54[222]

86

[210]

85

[209]

84

209

83

207

82

204

81

84

36

79

34

73

32

40

20

39

19

45

21

48

22

51

23

52

24

55

25

56

26

59

27

59

28

64

29

65

30

11

5

12

6

14

7

16

8

19

9

20

10 4

240

18

35.5

17

32

16

31

15

28

14

27

1370

31

75

33

80

35115

49

119

50

122

51

128

52

127

53

23

11

24

12

7

3

9

4

* 58 – 71 Lanthanum series

† 90 – 103 Actinium

series

a = relative atom

ic mass (ap

prox)

x = atom

ic symb

olb

= atom

ic numb

er

THE P

ERIO

DIC

TAB

LE OF ELEM

ENTS

Gro

up

abx

*†

1

1

12

34

56

78

910

1112

1314

1516

1718

III

IIIIV

VIVII

OV

Elemen

ts with

atom

ic nu

mb

ers 112-116 have b

een

repo

rted b

ut n

ot fu

lly auth

enticated


5

Data Leaflet

General Information 1 tonne = 106 g 1 metre = 109 nm One mole of any gas at 293K and a pressure of 1 atmosphere (105 Pa) occupies a volume of 24 dm3 Avogadro Constant = 6.02 x 1023 mol-1 Gas constant = 8.31 J mol-1 K-1 Planck Constant = 6.63 x 10-34 Js Specific Heat Capacity of water = 4.2 J g-1 K-1 Speed of Light = 3 x 108 ms-1

Characteristic absorptions in IR spectroscopy Wavenumber/cm-1 Bond Compound

550 – 850 C – X (X=Cl, Br, I) Haloalkanes 750 – 1100 C – C Alkanes, alkyl groups 1000 – 1300 C – O Alcohols, esters, carboxylic acids 1450 – 1650 C = C Arenes 1600 – 1700 C = C Alkenes 1650 – 1800 C = O Carboxylic acids, esters, aldehydes,

ketones, amides, acyl chlorides 2200 – 2300 C ≡ N Nitriles 2500 – 3200 O – H Carboxylic acids 2750 – 2850 C – H Aldehydes 2850 – 3000 3200 – 3600 3300 – 3500

C – H O – H N – H

Alkanes, alkyl groups, alkenes, arenes Alcohols Amines, amides

Proton Chemical Shifts in Nuclear Magnetic Resonance Spectroscopy (relative to TMS) Chemical Shift Structure

0.5 – 2.0 –CH Saturated alkanes 0.5 – 5.5 –OH Alcohols 1.0 – 3.0 –NH Amines 2.0 – 3.0 –CO–CH Ketones –N–CH Amines C6H5–CH Arene (aliphatic on ring) 2.0 – 4.0 X–CH X = Cl or Br (3.0 – 4.0)

X = I (2.0 – 3.0) 4.5 – 6.0 –C=CH Alkenes 5.5 – 8.5 RCONH Amides 6.0 – 8.0 C6H5 Arenes (on ring) 9.0 – 10.0 –CHO Aldehydes 10.0 – 12.0 –COOH Carboxylic acids

These chemical shifts are concentration and temperature dependent and may be outside the ranges indicated above.


6

1 In which species is the number of electrons equal to the number of neutrons?

A Be

B F–

C Na

D O2–

2 Which of the following states the name of a suitable indicator, together with the correct colour change at the end point, for the titration of ethanoic acid with sodium hydroxide solution?

© CCEA

indicator colour change at end point

A Methyl orange yellow to red

B Methyl orange red to yellow

C Phenolphthalein colourless to pink

D Phenolphthalein pink to colourless

sodium hydroxide solution

ethanoic acid + indicator

Section A – Multiple Choice

Select the correct response in each case and mark its code letter by connecting the dots as illustrated on the answer sheet.

Each multiple choice question is worth 1 mark.


7

3 Gallium nitride, GaN, is an ionic compound. The electronic configuration of the nitride ion in gallium nitride is:

A 1s2 2s2

B 1s2 2s2 2p3

C 1s2 2s2 2p4

D 1s2 2s2 2p6

4 Which of the following is the best oxidising agent? A Cl2

B CI–

C I2

D I–

5 Which of the following atoms obeys the octet rule?

A B in BF3

B Be in BeCl42–

C P in PCl5

D S in SF6

6 Which of the following does not have hydrogen bonding between its molecules?

A CHF3

B C2H5OH

C HF

D NH3


8

7 Which of the following is a polar molecule?

A BF3

B CCl4

C CS2

D NCl3

8 In the Periodic Table the element zinc belongs to:

A the d block

B the f block

C the p block

D the s block

9 The relative atomic mass is defined as:

A the average mass of an atom of an element relative to 1

12 of the mass of a carbon-12 atom

B the average mass of an element relative to 1

12 of the mass of a carbon atom

C the mass of an atom of an element relative to 1

12 of the mass of an atom of carbon-12

D the mass of an atom of an element relative to the mass of a hydrogen atom

10 Which of the following is not produced when concentrated sulfuric acid reacts with sodium bromide?

A bromine

B hydrogen bromide

C hydrogen sulfide

D sulfur dioxide


Examiner Only

Marks Re-mark

9[Turn over

Section B

Answer all six questions in this section

11 Electrons are found in shells, sub-shells and orbitals.

(a) (i) Explain what is meant by the term orbital.

[1]

(ii) Draw the shape of an s orbital.

[1]

(iii) Write the electronic configuration for an atom of copper.

[1]


Examiner Only

Marks Re-mark

10

(b) Successive ionisation energies provide evidence for the existence of different shells in an atom.

(i) On the axes below, sketch a graph of the successive ionisation energies of oxygen. [2]

(ii) Write an equation, including state symbols, to represent the second ionisation energy of oxygen.

[1]

(iii) Explain why the first ionisation energy of oxygen is less than the first ionisation energy of fluorine.

[3]

0 1 2 3 4 5 6 7 8

logionisation

energy

number of electrons removed


Examiner Only

Marks Re-mark

11 [Turn over

(c) Ionisation energies provide evidence for the order of elements in the Periodic Table.

The ionisation energies of some Group VI elements are shown in the table below.

element ionisation energy/kJ mol–1

Oxygen 1314

Sulfur 1000

Selenium 941

Tellurium 869

State and explain the trend in ionisation energies in this group.

[4]


Examiner Only

Marks Re-mark

12

12 Uranium, named after the planet Uranus, is a weakly radioactive metal used to fuel nuclear power plants. Uranium has properties and a structure typical of a metal.

(a) Describe the structure of uranium metal.

[2]

(b) The two most common isotopes of uranium are U235 and U238.

(i) Explain why U235 and U238 are isotopes.

[2]

(ii) The relative atomic mass of a sample of uranium containing the isotopes U235 and U238 is 237.979.

Calculate the percentage abundance of each isotope present in

the sample.

[3]


13 [Turn over

(i) Write an equation for the conversion of UF4 to U.

[2]

(ii) Write an equation for the conversion of UO2 to UF4.

[2]

(iii) Complete the table below.

compound oxidation state of uranium

UO2(NO3)2

UO3

UF4

[3]

(d) Uranyl nitrate, UO2(NO3)2, thermally decomposes to produce uranium trioxide.

UO2(NO3)2 → 2UO3 4NO2 O2

(i) What is the systematic name for NO2?

[1]

(ii) How would you show experimentally that oxygen was given off in this decomposition?

[1]

Examiner Only

Marks Re-mark

(c) The extraction of uranium from its ore can be represented by the following series of reactions.

HNO3 heat H2 HF Mg Ore → UO2(NO3)2 → UO3 → UO2 → UF4 → U


Examiner Only

Marks Re-mark

14

13 Boron nitride has the chemical formula BN and exists in two physical forms. The structures of these forms, A and B, are shown below, and they closely resemble the two allotropes of carbon.

Source: Adapted from Cambridge O Level Chemistry 5070 Paper 2 QA2 June 2009. Reproduced by permission of Cambridge International Examinations.

Boron nitride is used as a lubricant in pencil leads and is also used in cutting tools and drill bits.

(a) Suggest why boron nitride with structure A can be used in pencil leads.

[2]

(b) Suggest why boron nitride with structure B is hard.

[2]

(c) Suggest why boron nitride with structure B does not conduct electricity.

[1]

Structure A Structure B


Examiner Only

Marks Re-mark

15 [Turn over

14 Sunglasses can be made from photochromic glass which contains small amounts of silver(I) chloride and copper(I) chloride. As sunlight passes through the glass the silver ions are reduced to silver atoms which cluster together and block the transmittance of light resulting in the darkening of the glass. The chloride ions are oxidised to chlorine atoms.

(a) (i) Calculate the maximum mass of silver ions that can be formed from 0.287 g of silver(I) chloride.

[2]

(ii) Write an equation for the reduction of silver ions to silver atoms.

[1]

(b) When exposure to light ends, the chlorine atoms are reduced by the copper(I) ions into chloride ions, and the copper(II) ions produced then react with the silver atoms.

Write an ionic equation for the reaction of copper(I) ions with chlorine atoms.

[1]

(c) Copper(I) chloride, similar to that used in photochromic glass, can be prepared in the laboratory by reacting copper metal with copper(II) oxide and concentrated hydrochloric acid. The equation for the reaction is:

2HCl CuO Cu → 2CuCl H2O

(i) Explain, using oxidation numbers, why this is a disproportionation reaction.

[3]

(ii) Suggest why the copper(I) chloride forms as a precipitate in this reaction.

[1]GCE_CHEM_SAM_V.2 UPDATED_12.10.16

Examiner Only

Marks Re-mark

16

(d) Copper(II) chloride can be produced in the laboratory by the reaction of copper(II) carbonate with hydrochloric acid.

Calculate the volume of 1.0 M hydrochloric acid needed to react with copper(II) carbonate to produce 2.0 g of copper(II) chloride. Give your answer to 2 significant figures.

[3]


Examiner Only

Marks Re-mark

17 [Turn over

15 An interhalogen compound is a molecule containing two or more different halogen atoms.

(a) Chlorine trifluoride is an interhalogen compound with the formula ClF3. It was first prepared in 1930 by the reaction of chlorine with fluorine.

(i) Write an equation for the preparation of chlorine trifluoride.

[1]

(ii) Chlorine trifluoride bonds covalently.

Explain the meaning of the term covalent bond.

[2]

(iii) Draw a dot and cross diagram to show the bonding in chlorine trifluoride.

[2]


Examiner Only

Marks Re-mark

18

(b) Chlorine trifluoride reacts with arsenic pentafluoride as shown in the following equation:

ClF3 AsF5 → ClF2 AsF6

–

(i) Draw and name the shapes of AsF5 and ClF2. Explain the shape

of each molecule. AsF5

Name

ClF2

Name

[6]

(ii) Predict the bond angle in the ClF2 ion.

[1]


Examiner Only

Marks Re-mark

19 [Turn over

(c) Saturated fats contain single covalent bonds. Iodine monochloride is an interhalogen molecule used to determine how saturated a fat is.

(i) Show the polarity of the iodine-chlorine bond on the diagram below and explain why the bond is polar.

I–Cl

[2]

(ii) Explain why iodine monochloride has a higher boiling point than chlorine.

[4]


Examiner Only

Marks Re-mark

20

16 Sodium iodide is used to prevent iodine deficiency in the body. Iodised table salt contains one part sodium iodide to 100 000 parts of sodium chloride. Magnesium carbonate is also present as an anticaking agent.

(a) Describe how you could use chemical tests on a sample of iodised table salt, to prove that it contains sodium ions, halide ions and carbonate ions.

[4]


Examiner Only

Marks Re-mark

21 [Turn over

(b) (i) Sodium reacts with iodine to form sodium iodide.

2Na I2 → 2NaI

The melting points of each of these substances are shown in the table below.

solid melting point/°C

sodium 98

iodine 114

sodium iodide 662

Explain why there is a difference in the melting points of sodium, iodine and sodium iodide.

In your answer refer to the type of particle involved and the nature and relative strength of the attractive forces holding the particles together.

In this question you will be assessed on using your written communication skills including the use of specialist scientific terms.

[6]


Examiner Only

Marks Re-mark

22

(ii) State the colour of solid iodine and that of solid sodium iodide.

Iodine

Sodium iodide [2]

(c) Sodium iodide is produced in the reaction between iodine and sodium hydroxide.

Write an equation for this reaction.

[2]

(d) A sodium iodide solution was made in the laboratory by dissolving 46.0 g of sodium iodide in 25.0 g of water at 20 °C.

(i) Calculate the molarity of this sodium iodide solution. Give your answer to 3 significant figures.

[2]

(ii) Chlorine was bubbled through the sodium iodide solution.

State the colour change observed in the solution.

From to [1]


THIS IS THE END OF THE QUESTION PAPER


BLANK PAGE



INSTRUCTIONS TO CANDIDATESWrite your Centre Number and Candidate Number in the spaces provided at the top of this page.Write your answers in the spaces provided in this question paper.Answer all sixteen questions.

INFORMATION FOR CANDIDATESThe total mark for this paper is 90.Figures in brackets printed down the right-hand side of pages indicate the marks awarded to each question or part question.Quality of written communication will be assessed in Question 13(c)(i).A Data Leaflet including a Periodic Table of the Elements is included with this question paper.



Section A 1–10

Section B111213141516

TotalMarks

Chemistry


Further Physical and Inorganic Chemistry and an Introduction to Organic Chemistry


Centre Number

Candidate Number


2017


26

[227]

89

139

57

[256]

101

[223]

87

[226]

88

[261]

104

[262]

105

[266]

106

[264]

107

[277]

108

[268]

109

[271]

110

[272]

111

140

58

141

59

144

60

145

61

150

62

152

63

157

64

159

65

162

66

165

67

167

68

169

69

173

70

175

71232

90

[231]

91

238

92

[237]

93

[242]

94

[243]

95

[247]

96

[245]

97

[251]

98

[254]

99

[253]

100

[254]

102

[257]

103

133

55

137

56

178

72

181

73

184

74

186

75

190

76

192

77

195

78

197

79

201

80

89

39

91

40

103

45

85

37

88

38

93

41

96

42

[98]

43

101

44

106

46

108

47

112

48

131

54[222]

86

[210]

85

[209]

84

209

83

207

82

204

81

84

36

79

34

73

32

40

20

39

19

45

21

48

22

51

23

52

24

55

25

56

26

59

27

59

28

64

29

65

30

11

5

12

6

14

7

16

8

19

9

20

10 4

240

18

35.5

17

32

16

31

15

28

14

27

1370

31

75

33

80

35115

49

119

50

122

51

128

52

127

53

23

11

24

12

7

3

9

4



series

a = relative atom

ic mass (ap

prox)

x = atom

ic symb

olb

= atom

ic numb

er

THE P

ERIO

DIC

TAB

LE OF ELEM

ENTS

Gro

up

abx

*†

1

1

12

34

56

78

910

1112

1314

1516

1718

III

IIIIV

VIVII

OV

Elemen

ts with

atom

ic nu

mb

ers 112-116 have b

een

repo

rted b

ut n

ot fu

lly auth

enticated


27

Data Leaflet





C – H O – H N – H







28

1 The enthalpy change for the formation of ammonia is –46.2 kJ mol–1. What is the enthalpy change, in kJ, for the reaction 2NH3(g) → N2(g) 3H2(g)?

A –46.2

B 46.2

C 92.4

D –92.4

2 How many structural isomers of C4H10 exist?

A 2

B 3

C 4

D 5

3 A radical is a particle with:

A an unpaired electron

B a negative charge

C a positive charge

D a lone pair of electrons

4 Which of the following molecules has the highest boiling point? A CH2CH2

B CH3CH2OH

C CH3Cl

D CH3CH2CH3



Each multiple choice question is worth 1 mark.


29

5 Which of the following isomeric alcohols is resistant to oxidation?

A 2-methylbutan-1-ol

B 2-methylbutan-2-ol

C pentan-1-ol

D pentan-2-ol

6 Which of the following has a higher thermal stability than strontium carbonate?

A Barium carbonate

B Beryllium carbonate

C Calcium carbonate

D Magnesium carbonate

7 What volume of oxygen is required for the complete combustion of 100 cm3 of butane at room temperature and pressure?

A 400 cm3

B 500 cm3

C 650 cm3

D 1300 cm3

8 The reaction between ethene molecules is described as:

A elimination

B oxidation

C polymerisation

D substitution


30

9 The standard conditions referred to when calculating enthalpy changes are:

A 1 kPa and 273 K

B 100 kPa and 273 K

C 100 Pa and 298 K

D 100 kPa and 298 K

10 Which of the following decreases as Group II is descended from magnesium to barium?

A Atomic radius

B First ionisation energy

C Reactivity with water

D Solubility of the hydroxides


Examiner Only

Marks Re-mark

31 [Turn over

Section B

Answer all six questions in this section

11 Analysis of a compound, which contains carbon, hydrogen and bromine only, showed that 22.2% of its mass is carbon and 3.7% is hydrogen. The relative molecular mass of the compound is 216.0.

Calculate the molecular formula of the compound.

[3]


Examiner Only

Marks Re-mark

32

12 Petrol and diesel are both mixtures of hydrocarbons obtained from crude oil. Isomers of C5H12 are often included due to their capacity to prevent knocking, a problem which can lead to severe engine damage. The three structural isomers of C5H12 are shown below.

© CCEA

(a) Draw the structural formulae for isopentane and neopentane and give their IUPAC names.

[4]

(b) The three pentanes are regarded as structural isomers.

Explain this term.

[2]

name skeletal formula

n-pentane

isopentane

neopentane


Examiner Only

Marks Re-mark

33 [Turn over

(c) State and explain which isomer has the lowest boiling point.

[3]

(d) When ignited in a car engine, the hydrocarbons in the fuel undergo combustion.

Write an equation for the complete combustion of a pentane molecule.

[2]

(e) In the presence of ultraviolet light, alkanes undergo a radical substitution reaction.

Outline the mechanism of the reaction between pentane and chlorine in terms of initiation, propagation and termination steps.

Initiation

Propagation

Termination [4]


Examiner Only

Marks Re-mark

34

13 Many enthalpy changes, including enthalpies of combustion, can be determined by experiment. Others can be deduced using Hess’s Law.

(a) (i) State Hess’s Law.

[2]

(ii) Define the term standard enthalpy of combustion.

[3]

(iii) Use the standard enthalpies of formation given in the table below to calculate the enthalpy change for the complete combustion of methane:

CH4 2O2 → CO2 2H2O

compound fH⦵/kJ mol–1

CO2 –394

H2O –286

CH4 –75

[2]


Examiner Only

Marks Re-mark

35 [Turn over

(b) Enthalpy changes can also be calculated using average bond enthalpies. When bond enthalpies were used to estimate the enthalpy of reaction for the complete combustion of methane, it was found to have a value of –698 kJ mol–1.

(i) Explain why the value given above differs from the value obtained in (a)(iii).

[1]

(ii) Using the estimated enthalpy of reaction and the bond enthalpies given in the table below, calculate the bond enthalpy of the C–H bond in methane.

bond bond enthalpy/kJ mol–1

C O 743

O O 496

O H 463

[3]


Examiner Only

Marks Re-mark

36

(c) (i) Describe how you would experimentally determine the enthalpy of combustion of ethanol. Include in your answer the apparatus you would use, the measurements to be taken and how you would use your results to determine the enthalpy of combustion of ethanol.


[6]

(ii) Give two practical reasons why the experimental value obtained for the enthalpy of combustion of ethanol is significantly different from a value quoted in a data book.

[2]


Examiner Only

Marks Re-mark

37 [Turn over

14 The diagram shows a Maxwell-Boltzmann distribution curve for a mixture of sulfur dioxide and oxygen at temperature T.

Ea activation energy

© CCEA

(a) On the diagram, sketch the distribution curve for the same mixture at a higher temperature. [2]

(b) Use these distribution curves to explain why the reaction between sulfur dioxide and oxygen is faster at the higher temperature.

[2]

(c) Use the distribution curve to explain the role of a catalyst and why the reaction between sulfur dioxide and oxygen is faster in the presence of a catalyst.

[4]

Number ofmolecules

with agiven energy

EnergyEa


Examiner Only

Marks Re-mark

38

15 Halogenoalkanes are a useful class of organic compounds as they can undergo a number of important reactions.

(a) Bromoethane can be produced by an electrophilic addition reaction between ethene and hydrogen bromide.

(i) Explain why hydrogen bromide can be considered as an electrophile.

[2]

(ii) Draw a flow scheme to show the mechanism for the reaction between ethene and hydrogen bromide.

[4]


Examiner Only

Marks Re-mark

39 [Turn over

(b) When the reaction is repeated with 3-methylpent-2-ene a mixture of two halogenoalkane products is obtained.

(i) 3-methylpent-2-ene exists as geometric isomers.

Draw and label the E and Z isomers of the alkene.

[2]

(ii) Draw the structures of the two products obtained when hydrogen bromide reacts with 3-methylpent-2-ene and indicate the major and minor products.

[2]

(iii) Explain why the two halogenoalkane products in (ii) are not obtained in equimolar amounts.

[3]


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40

(c) The halogenoalkane, 2-bromobutane, reacts with aqueous sodium hydroxide to form butan-2-ol.

(i) Write an equation for the reaction between 2-bromobutane and sodium hydroxide.

[2]

(ii) Classify butan-2-ol as primary, secondary or tertiary, explaining your reasoning.

[2]

(d) When 2-bromobutane reacts with ethanolic sodium hydroxide, two alkene products are formed, one of which is but-1-ene.

(i) Write an equation for the reaction between 2-bromobutane and ethanolic sodium hydroxide to form but-1-ene.

[2]

(ii) Explain what is meant by the term ethanolic.

[1]

(iii) State the type of reaction between 2-bromobutane and ethanolic sodium hydroxide.

[1]

(iv) Name the other alkene that is produced in this reaction.

[1]


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41 [Turn over

16 The second stage in the production of nitric acid involves the reaction of nitrogen monoxide with oxygen to form nitrogen dioxide. When nitrogen monoxide and oxygen are mixed under suitable conditions a dynamic equilibrium is established.

2NO(g) O2(g) 2NO2(g) ∆H –116 kJ mol–1

(a) Explain what is meant by the term dynamic equilibrium.

[2]

(b) State and explain how increasing the pressure will affect the equilibrium yield of nitrogen dioxide.

[2]

(c) State and explain how increasing the temperature will affect the equilibrium yield of nitrogen dioxide.

[2]

(d) State and explain the effect a catalyst has on the equilibrium yield of nitrogen dioxide.


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42

(e) The position of the equilibrium is found to lie to the right, resulting in a high yield of nitrogen dioxide.

(i) Write an expression for the equilibrium constant, Kc, including the units.

[2]

(ii) What does the position of the equilibrium indicate about the magnitude of the equilibrium constant?

[1]

(f) Nitrogen dioxide is also produced when magnesium nitrate undergoes thermal decomposition.

2Mg(NO3)2(s) → 2MgO(s) 4NO2(g) O2(g)

Calculate the atom economy of the above reaction.

[2]


BLANK PAGE



INSTRUCTIONS TO CANDIDATESWrite your Centre Number and Candidate Number in the spaces provided at the top of this page.Write your answers in the spaces provided in this question paper.Answer all three questions.

INFORMATION FOR CANDIDATESThe total mark for this paper is 25.Figures in brackets printed down the right-hand side of pages indicate the marks awarded to each question or part question.A Data Leaflet including a Periodic Table of the Elements is included with this question paper.

Centre Number

Candidate Number


2017



123

TotalMarks

45

ChemistryAssessment Unit AS 3

Basic Practical Chemistry

Practical Booklet A



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C – H O – H N – H







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48

Safety glasses should be worn at all times and care should be exercised during the Practical examination.

1 You are provided with a mixture P. It contains a soluble part and an insoluble part.

(a) State its colour.

[1]

(b) How can you tell that there are two different substances in the mixture?

[2]

(c) Heat a spatula measure of the mixture in a boiling tube.

(i) Describe what you see happening in the boiling tube. Refer to the part which is heated, the middle of the boiling tube and the open end of the boiling tube.

[2]

(ii) A liquid is formed, describe its appearance, and test its pH using Universal Indicator solution.

[1]

(d) Place one spatula measure of the mixture onto a watch glass. Add some dilute hydrochloric acid to the mixture.

(i) Describe what happens to the mixture.


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49 [Turn over

(ii) Dip a piece of glass tubing into limewater and hold the glass tubing over the mixture whilst it is reacting.

Describe what happens to the limewater.

[1]

(e) Add 5 spatula measures of the mixture to 100 cm3 of warm water in a beaker. Warm the mixture with stirring for about 5 minutes. Filter the warm mixture into a conical flask.

Using a burette react 25 cm3 of the filtrate with 0.01 M hydrochloric acid using phenolphthalein as the indicator. Repeat the procedure using another 25 cm3 of the filtrate. Determine the volume of acid needed to the nearest cm3.

(i) Explain what you would use to measure out 25 cm3 of the filtrate.

[2]

(ii) Complete the table below. Include any missing labels and write the values observed in the reaction.

volume of acid at the start/cm3

volume of acid at the end/cm3

rough value

value 1

value 2

[6]

(f) Carry out a flame test on the mixture using a piece of nichrome wire. What colour is produced in the Bunsen flame?

[1]

limewater

glass tubing

watch glass

mixture

© CCEA


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50

2 You are supplied with three liquids X, Y and Z, in three separate test tubes. One of them is ethanol.

(a) Add a very small piece of sodium to each liquid and observe what happens. With each liquid state whether the sodium sinks or floats or moves up and down. State whether a gas is given off. Place any unreacted sodium, if any, back where it came from.

[3]

(b) Explain which liquid is ethanol.

[1]


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51 [Turn over

3 Substance Q is a white organic solid. Heat the solid on a piece of broken porcelain. Heat gently at first and then more strongly and then with a roaring flame.

(a) Describe what happens to the white solid when it is heated. There should be a minimum of three separate observations. The experiment may be repeated if you wish.

[2]

(b) Explain which observation suggests that the solid is organic.

[1]


Centre Number

Candidate Number


2017



1234

TotalMarks

53



Practical Booklet B


TIME

INSTRUCTIONS TO CANDIDATES

INFORMATION FOR CANDIDATES

Write your Centre Number and Candidate Number in the spaces provided at the top of this page.Write your answers in the spaces provided in this question paper.Answer all four questions.

The total mark for this paper is 55.Figures in brackets printed down the right-hand side of pages indicate the marks awarded to each question or part question.A Data Leaflet including a Periodic Table of the Elements is included with this question paper.

1 hour and 15 minutes.


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Data Leaflet





C – H O – H N – H







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56

1 The diagram below shows the reaction of sodium bromide or sodium chloride with concentrated sulfuric acid.

The gases produced in the reactions are passed through water which contains Universal Indicator solution. The gases travel at a speed which is proportional to their molecular masses.

(a) Describe what happens to the colour in the test tube when sodium chloride is reacted.

[2]

(b) Describe what happens to the colour in the test tube when sodium bromide is reacted.

[2]

water + universal indicatorsodium chloride/bromide

© CCEA


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57 [Turn over

2 A student is provided with a mixture of potassium carbonate and barium carbonate.

Describe how you would separate the two substances and show that barium carbonate was present.

[4]


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58

3 1-chlorobutane may be prepared as follows:

• Fit a 250 cm3 round-bottomed flask with a reflux condenser, the top of which is connected to apparatus for absorbing hydrogen chloride.

• Place 68 g (0.5 mol) of anhydrous zinc chloride and 40 cm3 of concentrated hydrochloric acid in the flask.

• Add 23 cm3 of butan-1-ol and gently reflux the mixture for 2 hours.

• Arrange the condenser for distillation and distil the mixture collecting the liquid which boils below 115 °C.

• Separate the upper layer of the distillate, mix it with an equal volume of concentrated sulfuric acid and transfer the mixture to a flask fitted with a reflux condenser.

• Reflux gently for 15–30 minutes and then distil the 1-chlorobutane from the acid at 76–79 °C.

• Wash the distillate successively with 25 cm3 of water, 10 cm3 of 1M sodium hydroxide solution and 25 cm3 of water.

• Leave the 1-chlorobutane over 2 g of anhydrous calcium chloride and distil from a small distillation flask.

• The 1-chlorobutane is collected at 75–78 °C.

(a) Draw a labelled diagram of apparatus which can absorb hydrogen chloride gas and explain how it works.

[3]

(b) Suggest the purpose of the anhydrous zinc chloride in the preparation of 1-chlorobutane.

[1]


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59 [Turn over

(c) The mixture is gently refluxed.

Explain the difference that you would observe between gentle and vigorous refluxing.

[1]

(d) Concentrated sulfuric acid is used to remove impurities which are not easily separated by distillation.

Suggest why these impurities are difficult to remove.

[1]

(e) The upper layer of the distillate is separated.

Suggest the name of the substance that forms the lower layer.

[1]

(f) The distillate is washed with water and sodium hydroxide solution.

Explain, giving full experimental detail, how this washing is carried out.

[4]

(g) Explain the use of the anhydrous calcium chloride and name an alternative substance that could be used.


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60

(h) Use the following method to calculate the mass of 1-chlorobutane obtained in the preparation.

(i) The density of butan-1-ol is 0.81.

State the units for density and use this information to calculate the mass of 23 cm3 of butan-1-ol.

[2]

(ii) Calculate the yield of 1-chlorobutane from this mass of butan-1-ol assuming the hydrochloric acid is in excess.

[2]

(i) The purity of the 1-chlorobutane may be judged from its boiling point. A student stated that the boiling point was 78.4 °C and a chemical data book quoted 77–78 °C.

Comment on these values and state why the 1-chlorobutane was collected at 75–78 °C.

[3]

(j) The infrared spectrum of the prepared 1-chlorobutane is a good indication of its purity.

Suggest how you could use the infrared spectrum to determine whether the 1-chlorobutane is 100% pure.

[2]


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61 [Turn over

4 The trends in the reaction of the Group II metals with steam can be investigated using the apparatus below.

The steam is passed over the heated metal and then into a container of water and the hydrogen produced is collected and measured.

(a) Write the equation, including state symbols, for the reaction of a Group II metal, M, with steam.

[2]

(b) In order for a valid comparison to be made the metals should be the “same”.

What three things would you do to ensure that the metals are the “same”?

[3]

(c) It might seem surprising that steam at a temperature of 100 °C is used rather than water at 25 °C.

(i) Suggest why it is safer to use steam rather than water.

[1]

(ii) State three observations for the reaction of calcium with water at 25 °C in a gas jar.

[3]

heat

steam

trough water

burette

M

© CCEA


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62

(d) The rate of hydrogen production is an indication of the rate of reactivity of the metal with steam. The graph below shows the result for magnesium.

(i) Label the axes on the graph including the units. [2]

(ii) Draw on the graph the expected result for calcium. [2]

(iii) Describe how you would obtain a sample of gas from the burette and use a chemical test to show that the gas was hydrogen.

[3]

(e) Calculate the volume of hydrogen collected from 3.40 g of calcium reacting with steam at 20°C and one atmosphere pressure.

Give your result to two significant figures.

[4]


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6310229.05 [Turn over

(f) A student suggested using similar apparatus to measure the trends in reaction of the Group II metals with oxygen.

Explain the difficulties that this method would pose and how they could possibly be overcome.

[5]




Section A 1–10

Section B11121314151617

TotalMarks

Chemistry

Assessment Unit A2 1

Further Physical and Organic Chemistry

[CODE]

SPECIMEN PAPER

Centre Number

Candidate Number

ADVANCEDGeneral Certificate of Education

2018

65

TIME

INSTRUCTIONS TO CANDIDATES

INFORMATION FOR CANDIDATES

2 hours

Write your Centre Number and Candidate Number in the spaces provided at the top of this page.Write your answers in the spaces provided in this question paper.Answer all seventeen questions.

The total mark for this paper is 110.Figures in brackets printed down the right-hand side of pages indicate the marks awarded to each question or part question.Quality of written communication will be assessed in Questions 13(c)(ii) and 17(b)(iii).A Data Leaflet including a Periodic Table of the Elements is included with this question paper.


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C – H O – H N – H







68

1 Propanone reacts with iodine in the presence of an acid according to the equation:

CH3COCH3(aq) I2(aq) → CH3COCH2I(aq) HI(aq)

The most appropriate method for investigating the rate of this reaction is

A titrating samples with an acid

B titrating samples with sodium thiosulfate

C using a graduated syringe

D weighing the reaction vessel

2 Heat is produced when magnesium reacts with sulfuric acid:

Mg(s) H2SO4(aq) → MgSO4(aq) H2(g)

Which one of the following is true for the reaction?

A ∆S is negative

B ∆H is positive

C ∆G is positive

D the reaction is feasible at any temperature

3 One mole of propanoic acid, one mole of methanol and two moles of water were mixed and allowed to reach equilibrium. At equilibrium 0.5 mole of methyl propanoate was present. The value of Kc for this reaction is

A 1.00

B 1.25

C 5.00

D 10.00



Each Multiple Choice question is worth 1 mark.


69

4 Which one of the following graphs shows a reaction that is first order with respect to reactant Z?

© CCEA

5 Which one of the following represents the units of Kc for the equilibrium shown below?

N2(g) 3H2(g) 2NH3(g)

A mol–2 dm–6

B mol–2 dm6

C mol2 dm–6

D mol2 dm6

Rate

[Z]A

Rate

[Z]B

[Z]

TimeC

Time

[Z]D


70

6 Which one of the following is the systematic name for the carboxylic acid shown below?

H — C — C — C — C — C

CH3

H

H

H

H

H

CH3

H

O

OH

A 1,4-dimethylpentanoic acid

B 2,5-dimethylpentanoic acid

C 2-methylhexanoic acid

D 5-methylhexanoic acid

7 Which one of the following compounds reacts with both LiAIH4 and PCI5?

A CH3CH2OH

B CH3CH2CHO

C CH3COCH3

D CH3CH2COOH

8 Which one of the following statements about the formation of an ester from ethanoyl chloride and propan-1-ol is correct?

A Concentrated sulfuric acid is required

B Heat is required

C The ester produced is called ethyl propanoate

D The reaction goes to completion

9 Butan-1-ol was reacted with an excess of propanoic acid in the presence of a small amount of concentrated sulfuric acid. 6.0 g of the alcohol produced 7.4 g of the ester. Which one of the following is the percentage yield of the ester?

A 57%

B 70%

C 75%

D 81%


71

10 Which one of the following salts will dissolve to produce a solution with the highest pH?

A Ammonium chloride

B Ammonium ethanoate

C Sodium chloride

D Sodium ethanoate


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72

Section B

Answer all seven questions in this section.

11 Data for the reduction of iron(lll) oxide by carbon, are shown in the table below.

2Fe2O3(s) 3C(s) → 4Fe(s) 3CO2(g)

substance ∆fH⦵/kJ mol–1 S⦵/J K–1 mol–1

Fe2O3 –824.2 87.4

C 0.0 5.7

Fe 0.0 27.3

CO2 –393.5 213.6

(a) (i) Calculate the values of ∆H⦵, ∆S⦵ and ∆G⦵ for the reaction at 298 K.

∆H⦵

[2]

∆S⦵

[2]

∆G⦵

[1]

(ii) Using your results from part (i) explain why this reaction is not feasible at 298 K.

[1]


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73 [Turn over

(b) Calculate the temperature above which this reaction is feasible.

[2]


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74

Mg2(g) 2e– 2F(g)

Mg2(g) 2e– F2(g)

Mg(g) F2(g)

12 The strength of the ionic bonding in compounds, such as magnesium fluoride and magnesium chloride, is related to the lattice enthalpy of the compound.

(a) Define the term lattice enthalpy.

[2]

(b) (i) Complete the Born-Haber cycle for magnesium fluoride:

[4]


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75 [Turn over

(ii) Using the data given below, calculate the lattice enthalpy for magnesium fluoride.

kJ mol–1

Standard enthalpy of formation for magnesium fluoride –1123First electron affinity of fluorine –348Atomisation enthalpy of fluorine 79First ionisation enthalpy of magnesium 736Second ionisation enthalpy of magnesium 1450Atomisation enthalpy of magnesium 150

[2]

(c) Magnesium fluoride and magnesium chloride are both soluble in water. Magnesium chloride has an enthalpy of solution of –155 kJ mol–1.

(i) Using diagrams, show how magnesium and fluoride ions interact with water molecules in an aqueous solution of magnesium fluoride.

[2]

(ii) Given that the enthalpies of hydration of magnesium ions and chloride ions are –1920 kJ mol–1 and –364 kJ mol–1 respectively, calculate the lattice enthalpy of magnesium chloride.

[2]


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76

13 Butanone reacts with hydrogen cyanide to form a product that contains an asymmetric centre.

The reaction mechanism is similar to that for the reaction between hydrogen cyanide and propanone.

(a) (i) Give the systematic name of the product.

[2]

(ii) What type of stereoisomerism is shown by the product?

[1]

(iii) Draw the 3D representations of the stereoisomers.

[2]

(iv) Name the mechanism for the reaction.

[1]

(v) Draw the mechanism for this reaction.

[4]

OH

C CN

CH3

CH3CH2

CH3CH2 — C — CN

OH

CH3


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77 [Turn over

(vi) Explain, in terms of the mechanism, why a racemic mixture is produced in this reaction.

[3]

(b) Butanal is a structural isomer of butanone.

Describe, giving practical details, how you would carry out a chemical test to distinguish between samples of butanal and butanone.

[3]


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78

(c) 2,4-dinitrophenylhydrazine reacts with both butanone and butanal to form 2,4-dinitrophenylhydrazones.

(i) Write the equation for the reaction of butanone with 2,4-dinitrophenylhydrazine.

[2]

(ii) Describe what is observed in these reactions and explain, experimentally, how the 2,4-dinitrophenylhydrazones can be used to confirm the identity of the reactant.


[6]


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79 [Turn over

14 At 25°C, the acid dissociation constant, Ka, for propanoic acid CH3CH2COOH, is 1.35 10–5 mol dm–3. A buffer solution can be prepared by mixing a solution of propanoic acid with a solution of sodium propanoate.

(a) (i) Write the expression for the acid dissociation constant of propanoic acid.

[1]

(ii) Calculate the pH of a 0.25 mol dm–3 solution of propanoic acid.

[3]

(iii) What is meant by the term buffer solution?

[2]

(iv) Calculate the pH of the buffer solution formed when 300 cm3 of a 0.25 mol dm–3 solution of propanoic acid is mixed with 200 cm3 of a 0.15 mol dm–3 solution of sodium propanoate.

[4]


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80

(b) The titration curve below shows the change in pH when a 0.20 mol dm–3 solution of sodium hydroxide is added, from a burette, to 25.0 cm3 of a solution of propanoic acid of unknown concentration.

© CCEA

(i) Write the equation for the neutralisation reaction which occurs.

[1]

(ii) Suggest a suitable indicator for this titration. Give the colour change and explain why the indicator is suitable.

[4]

(iii) Calculate the concentration of the propanoic acid.

[3]

pH

18.5 Volume of NaOH added (cm3)


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81 [Turn over

(iv) At 25 °C, Kw has the value 1.00 10–14 mol2 dm–6.

Calculate the pH of the 0.20 mol dm–3 solution of sodium hydroxide.

[2]


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82

15 Benzene is toxic and carcinogenic, however, the reactions of aromatic compounds can be studied in the laboratory using other substances such as methyl benzoate.

(a) The electrons in the π bonds in benzene are delocalised.

Draw two structures for benzene to show the p-orbitals before and after delocalisation.

before after

[2]

(b) Nitration of methyl benzoate can be achieved using a "nitrating mixture" of concentrated nitric and sulfuric acids.

(i) Write an equation to show how these two acids react when mixed.

[2]

(ii) Name the ion, produced in this reaction, which attacks the methyl benzoate molecule.

[1]


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83 [Turn over

(iii) Draw the mechanism of the mononitration of methyl benzoate and name the mechanism.

[5]

(iv) Name the organic product of this reaction.

[1]

(v) Describe the appearance of this organic product.

[1]


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84

16 The ionic equation for the alkaline hydrolysis of C4H9Br is shown below.

C4H9Br OH– → C4H9OH Br –

Data for this reaction is given in the table below.

experimentinitial

[C4H9Br](mol dm–3)

initial [OH–]

(mol dm–3)

initial rate(mol dm–3s–1)

1 0.02 0.02 40.0

2 0.01 0.02 20.0

3 0.03 0.04 60.0

(a) What is the order of the reaction with respect to C4H9Br? Explain your reasoning.

[2]

(b) What is the order with respect to OH–? Explain your reasoning.

[2]

(c) Write the rate equation for the reaction.

[1]

(d) Calculate a value for the rate constant and give its units.

[2]


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85 [Turn over

(e) Draw a reaction mechanism for the hydrolysis of C4H9Br which is consistent with your rate equation. Show the structure of C4H9Br clearly in your mechanism and identify the rate determining step.

[5]


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86

17 Fats and vegetable oils are triesters of long-chain carboxylic acids. Base catalysed hydrolysis of an oil produces glycerol and the sodium salt of octadeca-9,12-dienoic acid as the only products.

CH3(CH2)4CH=CHCH2CH=CH(CH2)7COOH

octadeca-9,12-dienoic acid

(a) (i) Draw the structure of glycerol.

[1]

(ii) State the systematic name for glycerol.

[1]

(iii) Draw the structure of the oil.

[1]


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87

(b) Simple monoesters, such as the one shown below, can be prepared by reacting carboxylic acids with alcohols:

(i) Give the systematic names of the carboxylic acid and alcohol required to prepare this ester.

Acid

Alcohol [1]

(ii) Write the equation for the formation of the ester.

[2]

(iii) Describe, giving experimental details, the preparation of a pure, dry sample of the ester.


[6]

H — C — C — C

CH3

H

H

O O— CH3CH3


TIME2 hours.

INSTRUCTIONS TO CANDIDATESWrite your Centre Number and Candidate Number in the spaces provided at the top of this page.Write your answers in the spaces provided in this question paper.Answer all seventeen questions.

INFORMATION FOR CANDIDATESThe total mark for this paper is 110.Figures in brackets printed down the right-hand side of pages indicate the marks awarded to each question or part question.Quality of written communication will be assessed in Questions 16(b)(ii) and 17(c).A Data Leaflet including a Periodic Table of the Elements is included with this question paper.

Chemistry


Analytical, Transition Metals, Electrochemistry and Organic Nitrogen Chemistry


Centre Number

Candidate Number


2018



Section A 1–10

Section B11121314151617

TotalMarks


90

[227]

89

139

57

[256]

101

[223]

87

[226]

88

[261]

104

[262]

105

[266]

106

[264]

107

[277]

108

[268]

109

[271]

110

[272]

111

140

58

141

59

144

60

145

61

150

62

152

63

157

64

159

65

162

66

165

67

167

68

169

69

173

70

175

71232

90

[231]

91

238

92

[237]

93

[242]

94

[243]

95

[247]

96

[245]

97

[251]

98

[254]

99

[253]

100

[254]

102

[257]

103

133

55

137

56

178

72

181

73

184

74

186

75

190

76

192

77

195

78

197

79

201

80

89

39

91

40

103

45

85

37

88

38

93

41

96

42

[98]

43

101

44

106

46

108

47

112

48

131

54[222]

86

[210]

85

[209]

84

209

83

207

82

204

81

84

36

79

34

73

32

40

20

39

19

45

21

48

22

51

23

52

24

55

25

56

26

59

27

59

28

64

29

65

30

11

5

12

6

14

7

16

8

19

9

20

10 4

240

18

35.5

17

32

16

31

15

28

14

27

1370

31

75

33

80

35115

49

119

50

122

51

128

52

127

53

23

11

24

12

7

3

9

4



series

a = relative atom

ic mass (ap

prox)

x = atom

ic symb

olb

= atom

ic numb

er

THE P

ERIO

DIC

TAB

LE OF ELEM

ENTS

Gro

up

abx

*†

1

1

12

34

56

78

910

1112

1314

1516

1718

III

IIIIV

VIVII

OV

Elemen

ts with

atom

ic nu

mb

ers 112-116 have b

een

repo

rted b

ut n

ot fu

lly auth

enticated


91

Data Leaflet





C – H O – H N – H







92

1 Which organic compound gives rise to the largest number of peaks in an nmr spectrum?

A CH3CH2COCH2CH3

B CH3COOH

C CH3CH2Br

D CH3CH2COOCH3

2 Which is correct for a lithium ion battery?

A Lithium ions move from the negative electrode to the positive electrode during discharge

B Lithium ions move from the positive electrode to the negative electrode during discharge

C The battery can be used safely at high temperature

D The electrolyte is an aqueous solution of a lithium salt

3 Which statement describes the primary structure of a protein?

A The folding of an alpha-helix

B The folding of a beta-pleated sheet

C The sequence of amino acids

D The coiling of the chains

4 Which one of the following describes the charge and coordination number of nickel in the [Ni(edta)]2– complex?

charge coordination number

A 2 1

B 2– 4

C 2 6

D 2– 8



Each Multiple Choice question is worth 1 mark.


93

5 Which one of the following ions is not present in a coloured compound?

A [Cu(NH3)4(H2O)2]2

B [Fe(SCN)(H2O)5]2

C [Ni(NH3)4(H2O)2]2

D [Zn(NH3)4(H2O)2]2

6 The standard electrode potentials for a series of redox equations are listed below.

Which element will reduce Fe3(aq) to Fe2(aq) but not to Fe(s)?

A Iodine

B Manganese

C Nickel

D Silver

7 Which one of the following pairs of monomers will not combine to form a polymer?

A HOOC(CH2)4COOH and H2N(CH2)6NH2

B H2N(CH2)6NH2 and H2N(CH2)6NH2

C CH2CH2 and CH2CH2

D HOOC(CH2)4COOH and HO(CH2)2OH

E /V

Mn2(aq) 2e– Mn(s) –1.19

Fe2(aq) 2e– Fe(s) –0.44

Ni2(aq) 2e– Ni(s) –0.25

I2(s) 2e– 2I–(aq) 0.54

Fe3(aq) e– Fe2(aq) 0.77

Ag(aq) e– Ag(s) 0.80


94

8 In the complex ion [MCl2(NH3)4], what is the oxidation number of M?

A 1

B 2

C 3

D 7

9 Iodoethane may be converted to propylamine by reaction with

A ammonia

B ammonia followed by LiAlH4

C potassium cyanide followed by ammonia

D potassium cyanide followed by LiAlH4

10 In a solution at pH 1 glycine exists as

A anions

B cations

C dipolar ions

D neutral molecules


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95 [Turn over

Section B

Answer all seven questions in this section.

11 The USA space programme supported research to develop fuel cells. The Shuttle missions used a fuel cell based on the reaction of hydrogen and oxygen in an alkaline medium to form water.

(a) Write equations to represent the electrode reactions in an alkaline hydrogen fuel cell.

Anode [1]

Cathode [1]

(b) Write an equation, including state symbols, for the overall reaction in the hydrogen-oxygen fuel cell.

[2]

(c) State two advantages of a hydrogen-oxygen fuel cell.

[2]


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96

12 Proteins are synthesised from 20 essential amino acids. Recent research has shown that some organisms also use another amino acid called selenocysteine, which is shown below.

H2N — C — COOH CH2SeH

CH3

(a) Explain why selenocysteine, like other amino acids, would be expected to have a high melting point.

[2]

(b) Selenocysteine reacts with sodium carbonate solution.

Write an equation for this reaction.

[2]

(c) Some E.coli bacteria contain selenoproteins which are enzymes.

(i) Draw the structure of the dimer formed between two selenocysteine molecules and circle the peptide link.

[3]


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97 [Turn over

(ii) Explain the mechanism by which the enzyme works.

[1]

(iii) Draw a graph, labelling the axes, to show how the enzyme activity is affected by altering the pH.

[2]


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98

13 The determination of iron in its ores is an example of the application of manganate(VII) titrations. Before titration with manganate(VII) ions any iron(III) must be reduced to iron(II). This reduction can be carried out with zinc amalgam (a mixture of zinc and mercury).

Zn2(aq) 2e– Zn(s) E –0.76 V

Fe2(aq) 2e– Fe(s) E –0.44 V

Fe3(aq) e– Fe2(aq) E +0.77 V

(a) (i) Write the equation for the reaction between zinc and iron(III) ions.

[1]

(ii) The use of zinc amalgam prevents the further reduction of iron(II) to iron.

Use the electrode potentials above to explain why, in theory, zinc would also reduce iron(II) to iron.

[1]

(b) Potassium manganate(VII) is used to determine the concentration of iron(II) in solution. The half-equations are:

MnO4– 8H 5e– → Mn2 4H2O

Fe2 → Fe3 e–

(i) Write an ionic equation for the reaction of acidified manganate (VII) with iron(II) ions.

[1]


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99 [Turn over

(ii) A sample of steel with a mass of 1.60 g was dissolved in an excess of dilute sulfuric acid and the solution made up to 250 cm3 with water. Several 25.0 cm3 samples of this solution, containing the iron(II) ions, were titrated with 0.02 mol dm–3 potassium manganate(VII) solution. The average titre was 26.0 cm3.

Calculate the percentage of iron in the sample of steel.

[4]

(iii) What is the colour change at the end point?

[2]


Examiner Only

Marks Re-mark

100

14 Amines may be prepared by the reduction of nitriles or by the reaction of ammonia with haloalkanes.

(a) 1-bromobutane reacts with ammonia (by a similar mechanism to that of the alkaline hydrolysis of haloalkanes) to form 1-aminobutane.

(i) Name the mechanism.

[1]

(ii) Write an equation for the reaction.

[1]

(iii) Without using a flow scheme suggest an explanation for the mechanism for the reaction.

[3]

(b) 1-aminobutane may also be prepared by the reduction of butanenitrile.

(i) Name a suitable reducing agent.

[1]

(ii) Using [H] to represent the reducing agent write an equation for the reduction of butanenitrile.

[2]

(c) Phenylamine (aniline) was discovered in 1826 by distilling the dye indigo. The name aniline is derived from anil, the Portuguese word for indigo. Reduction of nitrobenzene produces aniline.

Write the equation for the reduction of nitrobenzene using [H] to represent the reducing agent.

[2]


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101 [Turn over

(d) Aniline is basic and reacts with strong acids to form crystalline salts.

(i) State the basicity of aniline compared to ammonia and phenylethylamine, C6H5CH2CH2NH2.

[1]

(ii) Write the equation for the reaction of aniline with hydrochloric acid.

[1]

(iii) Explain why phenylethylamine is a primary amine.

[1]

(e) When aniline is treated with nitrous acid at a low temperature the benzenediazonium ion is formed.

(i) Draw the structure of the benzenediazonium ion, C6H5N2,

showing all the bonds between the nitrogen atoms and the location of the charge. Do not show the detailed structure of the benzene ring.

[2]

(ii) Name the reagents used to generate the nitrous acid.

[1]


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102

(iii) If a solution of benzenediazonium ion is treated with aqueous sodium cyanide in the presence of a copper catalyst, cyanobenzene is formed.

Name the reagents A – D in the following flow scheme.

C6H5N2 →

NaCN/CuC6H5CN

C6H5CH2NH2

→

→

A

C

C6H5COOH

C6H5CH2OH →D

C6H5CH2Cl

B

→

A _____________________________

B _____________________________

C _____________________________

D _____________________________ [4]


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Marks Re-mark

103 [Turn over

15 Transition metal chemistry is characterised by catalytic activity, redox reactions, colour changes and ligand replacement. Vanadium and chromium are typical transition metals.

(a) Explain, in terms of electronic structure, why vanadium and chromium are transition metals.

[1]

(b) An acidified solution of ammonium vanadate(V) undergoes a series of reductions when it is stirred with zinc.

(i) Complete the table below giving the colour of VO2(aq) and V3(aq) formed at the different stages of the reduction.

ion colour

VO2 Yellow

VO2(aq)

V3(aq)

V2(aq) Violet [2]

(ii) Chromium will also reduce ammonium vanadate(V).

E /V

Cr3(aq) 3e– Cr(s) –0.74

VO2(aq) 2H(aq) e– VO2(aq) H2O(l) 1.00

Write an equation for the reaction between chromium and VO2

(aq) ions and calculate the e.m.f. of the reaction.

[3]


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104

(c) The colour of a transition metal complex depends upon its coordination number and the ligands attached to the metal ion. This is illustrated by the following:

[Cu(H2O)6]2(aq) 4Cl–(aq) [CuCl4]2–(aq) 6H2O(l)

(i) State the colours of the two copper complexes.

[Cu(H2O)6]2(aq) _______________________________

[CuCl4]2–(aq) _______________________________ [2]

(ii) State the shape of the hexaaquacopper(II) ion.

[1]

(iii) Name a suitable reagent which could be added to the equilibrium to shift it to the right.

[1]

(d) 1,2-diaminoethane is a bidentate ligand which complexes with aqueous nickel(II) ions.

(i) Draw the structure of 1,2-diaminoethane.

[1]

(ii) What is meant by the term bidentate?

[1]


Examiner Only

Marks Re-mark

105 [Turn over

(iii) State the formula of the complex formed when excess 1,2-diaminoethane (represented as ‘en’) is added to aqueous nickel(II) ions.

[2]

(e) Trinitrotriammine cobalt(III), [Co(NO2)3(NH3)3], is a yellow crystalline substance which may be prepared by the following method.

Dissolve 12.2 g of cobalt(II) ethanoate tetrahydrate in 100 cm3 of hot water. Cool the solution in an ice bath and add 10.4 g of sodium nitrite dissolved in 50 cm3 of “0.88” ammonia. Cool to 10 °C and carefully add 14 cm3 of 20 volume hydrogen peroxide solution followed by 2 g of activated charcoal. After stirring, the mixture is left for 10 minutes before boiling for 30 minutes. Filter the hot solution to remove the activated charcoal and cool the filtrate in an ice bath. Filter off the crystals, wash with cold ethanol and dry.

(i) Deduce the formula of cobalt(II) ethanoate tetrahydrate.

[2]

(ii) State and explain the role of hydrogen peroxide in this preparation.

[2]

(iii) Suggest the shape of the trinitrotriammine cobalt(III) complex.

[1]

(iv) Deduce the coordination number of cobalt in the trinitrotriammine cobalt(III) complex.

[1]


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Marks Re-mark

106

(v) 20 volume hydrogen peroxide is so named because 1 cm3 of the solution produces 20 cm3 of gaseous oxygen on complete decomposition at 20 °C and one atmosphere pressure.

2H2O2(aq) → 2H2O(l) O2(g)

Calculate the concentration of 20 volume hydrogen peroxide in mol dm–3.

[3]


Examiner Only

Marks Re-mark

107 [Turn over

16 Propanoic acid and ethyl methanoate are isomers which can be identified using spectroscopic techniques.

(a) (i) Explain why propanoic acid and ethyl methanoate are regarded as isomers.

[2]

(ii) Write the equation for the formation of ethyl methanoate by an esterification reaction with ethanol.

[2]

(iii) The esterification is an equilibrium reaction.

Explain how you would increase the yield of ethyl methanoate.

[2]

(b) The nmr spectrum of ethyl methanoate is shown below.

© CCEA

(i) Name the substance responsible for the signal at 0 and state its formula.


Examiner Only

Marks Re-mark

108

(ii) Explain the nmr spectrum of ethyl methanoate with reference to spin-spin splitting, peak integration and chemical shift.


[6]


Examiner Only

Marks Re-mark

10910229.03 [Turn over

(c) The mass spectrum of ethyl methanoate is shown below.

28

31

45

74

20 30 40 50 60 70 80m/e

100

80

60

40

20

0

relativeabundance

© CCEA

Identify the ions responsible for the peaks.

m/e ion

28 ________________________

45 ________________________ [2]

(d) (i) Explain how the absorption of radiation by molecules gives rise to infrared spectra and how you would use infrared spectroscopy to distinguish between propanoic acid and ethyl methanoate.

[4]

(ii) How would you distinguish between propanoic acid and ethyl methanoate using a chemical test?

[2]


Examiner Only

Marks Re-mark

110

17 For a long time the bark of the willow tree (salix alba) was used to relieve fever symptoms. The active ingredient is salicylic acid but it has some undesirable side effects. In 1899 the ethanoate ester of salicylic acid was found to reduce these side effects. It was given the trade name Aspirin.

(a) Aspirin is prepared by reacting ethanoic anhydride, C4H6O3, with 2-hydroxybenzoic acid.

Using molecular formulae write an equation for this reaction.

[2]

(b) What property of Aspirin allows the crude Aspirin formed in this reaction to be washed with chilled water as part of the purification process?

[1]

(c) Describe, giving full experimental detail, the TLC method which can be used to investigate the purification process. The developing solvent is ethyl ethanoate.


[6]

(d) Suggest why TLC is preferable to GLC for this preparation.

[1]


BLANK PAGE



INSTRUCTIONS TO CANDIDATESWrite your Centre Number and Candidate Number in the spaces provided at the top of this page.Write your answers in the spaces provided in this question paper.Answer all five questions.


ChemistryAssessment Unit A2 3

Further Practical Chemistry

Practical Booklet A


Centre Number

Candidate Number


2018



1 2 3 4 5

TotalMarks


114

[22

7]

89

13

9

57

[25

6]

10

1

[22

3]

87

[22

6]

88

[26

1]

10

4

[26

2]

10

5

[26

6]

10

6

[26

4]

10

7

[27

7]

10

8

[26

8]

10

9

[27

1]

11

0

[27

2]

11

1

14

0

58

14

1

59

14

4

60

14

5

61

15

0

62

15

2

63

15

7

64

15

9

65

16

2

66

16

5

67

16

7

68

16

9

69

17

3

70

17

5

71

23

2

90

[23

1]

91

23

8

92

[23

7]

93

[24

2]

94

[24

3]

95

[24

7]

96

[24

5]

97

[25

1]

98

[25

4]

99

[25

3]

10

0

[25

4]

10

2

[25

7]

10

3

13

3

55

13

7

56

17

8

72

18

1

73

18

4

74

18

6

75

19

0

76

19

2

77

19

5

78

19

7

79

20

1

80

89

39

91

40

10

3

45

85

37

88

38

93

41

96

42

[98

]

43

10

1

44

10

6

46

10

8

47

11

2

48

13

1

54

[22

2]

86

[21

0]

85

[20

9]

84

20

9

83

20

7

82

20

4

81

84

36

79

34

73

32

40

20

39

19

45

21

48

22

51

23

52

24

55

25

56

26

59

27

59

28

64

29

65

30

11

5

12

6

14

7

16

8

19

9

20

10

4

240

18

35

.5

17

32

16

31

15

28

14

27

1370

31

75

33

80

35

11

5

49

11

9

50

12

2

51

12

8

52

12

7

53

23

11

24

12

7

3

9

4

* 58 – 71 Lanth

anu

m series

† 90 – 103 Actin

ium

series

a = relative ato

mic m

ass (app

rox)x =

atom

ic symb

ol

b =

atom

ic nu

mb

er

THE P

ERIO

DIC

TAB

LE OF ELEM

ENTS

Gro

up

abx

*†

1

1

12

34

56

78

910

1112

1314

1516

1718

III

IIIIV

VI

VII

OV

Elemen

ts with

atom

ic nu

mb

ers 11

2-1

16

have b

een

repo

rted b

ut n

ot fu

lly auth

enticated


115





C – H O – H N – H







Examiner Only

Marks Re-mark

116

Safety glasses should be worn at all times and care should be exercised during practical examinations.

1 You are required to titrate standard potassium manganate(VII) solution against sodium ethandioate.

5Na2C2O4 2KMnO4 8H2SO4 → K2SO4 2MnSO4 10CO2 8H2O 5Na2 SO4

You are provided with: • a solution of sodium ethanedioate • four 20 cm3 portions of sulfuric acid • potassium manganate(VII) solution of concentration 0.20 mol dm–3

You should: 1 Rinse out and fill the burette with the potassium manganate(VII)

solution 2 Using a pipette add 25 cm3 of the sodium ethandioate solution to a

conical flask 3 Add a portion of sulfuric acid to the conical flask 4 Warm the conical flask to slightly above room temperature 5 Titrate the potassium manganate(VII) solution against the sodium

ethandioate solution

(a) Complete the following results table.

burette reading at the start/cm3

burette reading at the end/cm3

volume of potassium

manganate(VII) added/cm3

rough titration

accurate titration

accurate titration

Average titration value __________________________ [6]

(b) Explain how you would read the value of the volume of potassium manganate(VII) in the burette.

[2]

(c) What is the colour change in the conical flask?

[2]


Examiner Only

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117 [Turn over

2 The solid provided is an iron compound.

Carry out the following tests to determine which iron compound it is. Write what is observed in each case.

(a) Describe the appearance of the solid.

[1]

(b) Dissolve the solid in water and state the colour of the solution.

[1]

(c) Add sodium hydroxide solution to part of the solution.

[1]

(d) Add dilute ammonia solution to part of the solution.

[1]

(e) Add barium chloride solution to part of the solution.

[1]

(f) Add silver nitrate solution to part of the solution.

[1]

(g) Name the iron compound.

[1]


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118

3 The depth of colour of a solution can be used to determine the formula of a coloured complex. In order to do this, solutions of various depths of colour, in test tubes, are compared with that of a standard solution. The reverse can be carried out. A concentrated solution of a coloured compound can be successively diluted until the depth of its colour matches that of a known solution.

(a) You are provided with a concentrated solution X of copper(II) sulfate of known concentration 5M and a solution of unknown concentration Y.

Dilute the solution X until it has the same colour as that of solution Y.

Explain your “dilutions” by stating the volumes and apparatus used and how you compared the colour of the known solution with that of the unknown solution.

[4]

(b) What is the concentration of the unknown solution?

[1]


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119 [Turn over

4 Z is an organic substance. Dissolve a couple of crystals of Z in an ignition tube a third filled with propanone. Dip a capillary tube into the liquid and place a spot of the solution onto a TLC plate. Let the propanone evaporate. Cut the TLC plate to fit a 250 cm3 beaker and place it in the beaker which contains ethanol and has a lid. Allow the ethanol to run to near the top of the TLC plate. Remove the TLC plate, leave for a couple of minutes and place in a container of iodine which is in a fume cupboard.

(a) Draw a sketch of the result after placing the TLC plate in iodine. Label the solvent front and the starting point.

[3]

(b) How many substances are there in Z?

[1]


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120

5 Solutions L1, L2 and L3 contain three different ligands. One of them is monodentate and the others are bidentate and polydentate. All of them form complexes with copper(II) ions.

Complete the following table which shows a “competition” between the ligands. Each box in the table should have a description of the change of colour or lack of change of colour which takes place when the solutions are mixed. The greater number of reactions will lead to the ligand with the greatest denticity.

Ligand 1 Ligand 2 Ligand 3

Copper(II) complex with ligand 1



[4]


BLANK PAGE



INSTRUCTIONS TO CANDIDATESWrite your Centre Number and Candidate Number in the spaces provided at the top of this page.Write your answers in the spaces provided in this question paper.Answer all four questions.


Centre Number

Candidate Number

General Certificate of Education2018



1 2 3 4

TotalMarks

123

ChemistryAssessment Unit A2 3


Practical Booklet B



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125

Data Leaflet





C – H O – H N – H







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126

1 A sample of a mixture of hydrocarbons was injected into a GLC machine. The trace obtained is shown below.

© CCEA

(a) What are the labels along the x axis and the y axis?

[2]

(b) How many substances are present in the sample?

[1]

(c) The relative areas of each signal are indicated on the trace.

Calculate the percentage purity of the major component in the mixture.

[2]

3 2 15 8


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127 [Turn over

2 You are supplied with a mixture of two crystalline solids. The solids are iron(II) sulfate and hydrated copper(II) sulfate.

(a) Describe the appearance of the mixture.

[2]

(b) The mixture was added to water and stirred with excess concentrated ammonia solution. The mixture was filtered.

(i) State the name and colour of the solid obtained on the filter paper.

[2]

(ii) State the formula and the colour of the filtrate.

[2]

(iii) How would you show that the sulfate anion was present in the filtrate?

[2]


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128

3 The structure of 1-phenylazonaphth-2-ol is shown below:

© CCEA

The preparation is as follows:

Dissolve 5.0 g of phenylamine in 16 cm3 of concentrated hydrochloric acid and 16 cm3 of water contained in a small beaker. Diazotise by the addition of a solution of 40 g of sodium nitrite in 20 cm3 of water. The temperature is maintained at 0–5 °C. The aqueous solution of sodium nitrite is added in portions until after 4 minutes the solution gives an immediate positive test for excess of nitrous acid with moist potassium iodide starch paper. Any precipitated phenylamine hydrochloride dissolves during the diazotisation to give a clear solution of the highly soluble diazonium salt.

Prepare a solution of 7.0 g of naphth-2-ol in 45 cm3 of 10% sodium hydroxide solution in a 250 cm3 beaker and cool the solution to 5 °C. Add the cold diazonium salt solution very slowly. A red colour develops and red crystals of 1-phenylazonaphth-2-ol soon separate. When all the diazonium salt solution has been added allow the mixture to stand in an ice bath for 30 minutes with occasional stirring. Filter the solution through a Buchner funnel with gentle suction, wash well with water and drain thoroughly by pressing the crystals. Recrystallise the product from pure ethanoic acid. Filter the recrystallised product with suction, wash with a little ethanol and dry between filter paper. The yield of deep red crystals is 3.0 g. The melting point is 131–2 °C.

(a) Explain why phenylamine is more soluble in hydrochloric acid than in water.

[2]

(b) Explain why the temperature is maintained at 0–5 °C.

[2]

HO

NN


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129 [Turn over

(c) Nitrous acid forms iodine which reacts with potassium iodide starch paper.

Explain what a positive result will be.

[2]

(d) The diazonium salt contains a benzene ring.

Why would you expect it to be highly soluble in water?

[2]

(e) How would you adjust Buchner filtration to achieve gentle suction?

[2]

(f) What is the advantage in washing the 1-phenylazonaphth-2-ol with ethanol?

[2]

(g) Explain how you would determine the melting point of 1-phenylazonaphth-2-ol.

[5]


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130

(h) Calculate the percentage yield of 1-phenylazonaphth-2-ol to one decimal place.

[5]

4 The compound nitramide, NO2NH2, is a white crystalline solid at room temperature. It is readily soluble in water in which it decomposes at a measurable rate according to:

NO2NH2(aq) → N2O(g) H2O(l)

Nitrogen(I) oxide, is insoluble in water.

(a) (i) Draw a labelled diagram to show how you would carry out this experiment and explain the procedure.

[5]

(ii) What is the main factor that needs to remain constant in the experiment to obtain valid results?

[1]


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131 [Turn over

(iii) A student suggested that a method of measuring the speed of the reaction would be to count the number of bubbles which were being produced.

Explain why this would not be a good method.

[1]

(iv) Suggest why nitramide is very soluble in water.

[2]

(b) Starting with 100 cm3 of a 0.50 M solution of nitramide in water the volume of nitrogen(I) oxide evolved, measured at 20 °C and a pressure of one atmosphere, was as follows:

volume of nitrogen(I) oxide/cm3 0.0 5.60 11.20 18.0 22.4

time/seconds 0 500 1000 1500 2000

(i) Explain which one of these results would not be used in the calculation of the rate of evolution of nitrogen(I) oxide.

[2]

(ii) Calculate the percentage of the nitramide, as a whole number, that has decomposed after 1000 seconds.

[3]

(iii) Given that the initial reaction rate is 5 10–6 mol dm–3 s–1 and the rate law is R k[NO2NH2], calculate the rate constant for the reaction and state its units.


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132

(c) A proposed mechanism for the decomposition of nitramide is:

NH2NO2(aq) → NO2NH–(aq) H(aq)

NO2NH–(aq) → N2O(g) OH–(aq)

H(aq) OH–(aq) → H2O(aq)

(i) Suggest and explain the rate determining step.

[2]

(ii) Give the formula of the reactive intermediate.

[1]

(iii) Suggest whether the proposed mechanism explains the order of the reaction.

[2]

(d) Nitrogen(I) oxide is also formed when ammonium nitrate decomposes.

NH4NO3 → N2O 2H2O

(i) Describe how you could prove the presence of ammonium ions in solid ammonium nitrate.

[3]

(ii) How could you distinguish between solid samples of ammonium nitrate and nitramide?

[1]


BLANK PAGE


APPARATUS AND MATERIALS

DIVIDER FRONT


APPARATUS AND MATERIALS

DIVIDER BACK


APPARATUSAND

MATERIALSLIST

[CODE]SPECIMEN


2017



Practical Booklet A


138

Advice for centres

• All chemicals used should be at least laboratory reagent specification and labelled with appropriate safety symbols, e.g. irritant.

• For centres running multiple sessions – candidates for the later session should be supplied with clean, dry glassware. If it is not feasible then glassware from the first session should be thoroughly washed, rinsed with deionised water and allowed to drain.

• Ensure all chemicals are in date otherwise expected observations may not be seen.


139

Each candidate must be supplied with safety goggles or glasses.

Question 1

Each candidate must be supplied with:

• a piece of glass tubing, 3 mm in diameter and between 10 and 15 cm long

• a spatula

• a heatproof mat

• a Bunsen burner

• a watch glass

• a boiling tube

• a test tube/boiling tube rack

• a spatula

• a heatproof mat

• a Bunsen burner

• a glass stirring rod


• a test tube/boiling tube holder

• one 50 cm3 burette of at least class B quality

• a funnel for filling the burette

• a filter funnel and three sheets of filter paper

• a retort stand and clamp

• a beaker of 100 cm3 capacity


• a measuring cylinder of 100 cm3 capacity

• one 25 cm3 pipette of at least class B quality

• a safety pipette filler

• two conical flasks of 250 cm3 capacity

• phenolphthalein indicator with dropper


140

• Universal Indicator solution with dropper

• a white tile or white paper

• a wash bottle containing deionised/distilled water

• nichrome wire

• 5 g of a 50/50 mixture of calcium hydroxide, which has been moistened with a few drops of water (the water should be absorbed and not visible), and calcium carbonate granules/chips (which are of greater particle size than the calcium hydroxide) labelled P and irritant

• 150 cm3 of 0.01 M hydrochloric acid labelled 0.01 M and corrosive/irritant

• about 10 cm3 of a saturated solution of calcium hydroxide in a reagent bottle/beaker labelled limewater (made fresh)

• about 10 cm3 of dilute hydrochloric acid in a stoppered reagent bottle labelled dilute hydrochloric acid and corrosive/irritant. This solution should be approximately 2 M.

• about 10 cm3 of concentrated hydrochloric acid in a stoppered reagent bottle labelled concentrated hydrochloric acid and corrosive

Question 2


• three test tubes

• a test tube/boiling tube holder


• a spatula

• a heatproof mat

• a Bunsen burner

• deionized/distilled water

• 20 cm3 of ethanol labelled Y and flammable

• 20 cm3 of propanone labelled X and flammable

• 20 cm3 of propanone mixed with a few drops of water labelled Z and flammable

• 3 rice grain sized pieces of sodium (they may still contain oil)


141

Question 3

• 3 g of citric acid labelled Q and irritant

• a heatproof mat

• a Bunsen burner

• two pieces of broken porcelain not less than 2 cm in width

• a pair of tongs

AS 3 Chemistry Practical Risk AssessmentChemical Notes Emergency actionHydrochloric acid(2 and 0.01 M)

Low hazard Even at this low concentration it may still cause harm in the eyes or in a cut.

In the eye: flood the eye with gently-running tap water for 10 minutes. See a doctor.Swallowed: do no more than wash out the mouth with water. Do not induce vomiting. Sips of water may help cool the throat and help keep the airway open. See a doctor.Spilt on the skin or clothing: remove contaminated clothing. Especially with concentrated acid, quickly use a dry cloth or paper towel to wipe as much liquid as possible off the skin. Then drench the skin with plenty of water. If a large area is affected or blistering occurs, see a doctor.Spilt on the floor, bench, etc.: wipe up small amounts with a damp cloth and rinse it well. For larger amounts, and especially for (moderately) concentrated acid, cover with mineral absorbent (e.g. cat litter) and scoop into a bucket. Neutralise with sodium carbonate. Rinse with plenty of water.

Calcium hydroxide

IRRITANT

Irritating to the eyes and skin.

In the eye: flood the eye with gently-running tap water for at least 20 minutes. See a doctor. If a visit to hospital is necessary, continue washing the eye during the journey in an ambulance.Swallowed: do no more than wash out the mouth with water. Do not induce vomiting. Sips of water may help cool the throat and help keep the airway open. See a doctor.Spilt on the skin or clothing: remove contaminated clothing. Drench the skin with plenty of water. If a large area is affected or blistering occurs, see a doctor.Spilt on the floor, bench, etc.: wipe up small amounts with a damp cloth and rinse it well. For larger amounts, and especially for (moderately) concentrated solutions, cover with mineral absorbent (e.g. cat litter) and scoop into a bucket. Neutralise with citric acid. Rinse with plenty of water.

Phenolphthalein Not classified as hazardous but shouldbe used with caution. Skin contamination should be avoided.

In the eye: flood the eye with gently-running tap water for at least 10 minutes. See a doctor.Swallowed: do no more than wash out the mouth with water. Do not induce vomiting. Sips of water may help cool the throat and help keep the airway open. See a doctor.Spilt on the skin or clothing: remove contaminated clothing. Wash off the skin with soap and plenty of water. Rinse contaminated clothing.Spilt on the floor, bench, etc.: wipe up with a damp cloth and rinse it well.


142

Citric acid IRRITANT

It is irritating to eyes.It is an approved food additive, E330.

In the eye: flood the eye with gently-running tap water for 10 minutes. See a doctor if pain persists.Swallowed: do no more than wash out the mouth with water. Do not induce vomiting. Sips of watermay help cool the throat and help keep the airway open. See a doctor.Spilt on the skin or clothing: remove contaminated clothing. Then drench the skin with plenty of water.Spilt on the floor, bench, etc.: wipe up small amounts with a damp cloth and rinse it well.For large spills, cover with mineral absorbent (e.g. cat litter) and scoop into a bucket. Neutralise with sodium carbonate. Rinse with plenty of water.

Chemical Notes Emergency actionCalcium carbonate

Low hazard Calcium carbonate occurs naturally as marble, chalk and limestone.It decomposes if heated above 800 °C and gives carbon dioxide with acids (unless the calcium salt is insoluble). It is an approved food additive, E170. Blackboard chalk may be calcium carbonate but is more likely to be calcium sulfate.

Ethanol There is a serious risk of liquid catching fire; its vapour may catch fire above 13°C. Breathing vapour may result in sleepiness

In the eye: flood the eye with gently-running tap water for 10 minutes. See a doctor.Swallowed: do no more than wash out the mouth with water. Do not induce vomiting. Sips of water may help cool the throat and help keep the airway open. See a doctor. NB: The casualty may show signs of drunkenness.Spilt on the skin or clothing: remove contaminated clothing and rinse it. Wash the affected area and clothing with plenty of water.Clothing catches fire – smother flames on clothing or the skin with a fire blanket or other material. Cool any burnt skin with gently- running tap water for 10 minutes.Other ethanol fires: allow fires in sinks, etc. to burn out. Fires at the top of test tubes, beakers, etc. should be smothered with a damp cloth or heat-proof mat.Spilt on the floor, bench, etc.: extinguish all Bunsen-burner flames. Wipe up small amounts with a cloth and rinse it well. For larger amounts, open all windows, cover with mineral absorbent (e.g. cat litter), scoop into a bucket and add water.NB. Ethanol should not be heated with a Bunsen burner. If heating is required, place the test tube of ethanol in a beaker of boiling water from a kettle (the beaker should be on a heatproof mat).


143

Calcium hydroxide

It is not officially classified, but there is a risk of serious damage to the eyes. It is irritating to the skin, lungs, etc.For a 15-minute exposure, the concentration of the powder in theatmosphere should not exceed 15 mg m-3

Solid: flood the eye with gently-running tap water for at least 20 minutes. See a doctor. If a visit to hospital is necessary, continue washing the eye during the journey in an ambulance.Limewater is unlikely to cause serious problems; flood the eye with gently-running tap water for at least 10 minutes. See a doctor if there are any concerns.Swallowed: Do no more than wash out the mouth with water. Do not induce vomiting. Sips of water may help cool the throat and help keep the airway open. Limewater is unlikely to cause serious problems. Wash out the mouth. See a doctor if there are any concerns.Spilt on the skin or clothing: Brush off the solid. Remove contaminated clothing. Drench the skin with plenty of water. If a large area is affected or blistering occurs, see a doctor. For limewater, wash with water.Spilt on the floor, bench, etc. Wipe up limewater or small amounts of solid with a damp cloth and rinse it well. For larger amounts of solid, scoop into a bucket, add water to the area followed by mineral absorbent (e.g. cat litter).

Chemical Notes Emergency actionPropanone There is a serious

risk of the liquid catching fire.Its vapour may catch fire above -20°C.It can cause severe eye damage and will degrease the skin.For a 15-minute exposure, the concentration in the atmosphereshould not exceed 3620 mg m-3. The smell can be detected by most

In the eye: flood the eye with gently-running tap water for 10 minutes. See a doctor.Vapour breathed in: remove the casualty to fresh air. Keep him/her warm. See a doctor if breathing is difficult.Swallowed: do no more than wash out the mouth with water. Do not induce vomiting. Sips of water may help cool the throat and help keep the airway open. See a doctor.Clothing catches fire: smother flames on clothing or the skin with a fire blanket or other material. Cool any burnt skin with gently-running tap water for 10 minutes.Other propanone fires: allow fires in sinks, etc. to burn out. Fires at the top of test tubes, beakers, etc. should be smothered with a damp cloth or heat-proof mat.Spilt on the skin or clothing: remove contaminated clothing. If more than a test-tube amount was involved, wash theaffected area and clothing with plenty of water.Spilt on the floor, bench, etc.: put out all Bunsen-burner flames. Wipe up small amounts with a cloth and rinse it well. For larger amounts, open all windows, cover with mineral absorbent (e.g. cat litter), scoop into a bucket and add water.


144

Concentrated hydrochloric acid

CORROSIVE

It causes burns. The vapour irritates the lungs.

In the eye: flood the eye with gently-running tap water for 10 minutes. See a doctor.Vapour breathed in: remove to fresh air. Call a doctor if breathing is difficult.Swallowed: do no more than wash out the mouth with water. Donot induce vomiting. Sips of water may help cool the throat and help keep the airway open. See a doctor.Spilt on the skin or clothing: remove contaminated clothing. Then drench the skin with plenty of water. If a large area is affected or blistering occurs, see a doctor.Spilt on the floor, bench, etc.: for release of gas, consider the need to evacuate the laboratory and open all windows. For large spills, and especially for (moderately) concentrated acid, cover with mineral absorbent (e.g. cat litter) and scoop into a bucket.Neutralise with sodium carbonate. Rinse with plenty of water. Wipe up small amounts with a damp cloth and rinse it well.

Chemical Notes Emergency actionLimewater Even a saturated solution of calcium hydroxide is so dilute that

it is not classed as irritant. However, sometimes the solution is made up from solid calcium hydroxide which is irritating to the eyes and skin.

Sodium Reacts violently with water.

It burns vigorously and is difficult to extinguish.

It causes burns contact with moisture produces

In the eye: flood the eye with gently-running tap water for at least 20 minutes. See a doctor. If it is necessary to go to hospital, continue washing the eye during the journey in an ambulance.Swallowed: do no more than wash out the mouth with water. Do not induce vomiting. Sips of water may help cool the throat and help keep the airway open. See a doctor. Spilt on the skin or clothing: remove any pieces of solid with forceps. Then drench the skin with plenty of water. If a largearea is affected or blistering occurs, see a doctor.

sodium hydroxide which is corrosiveIt reacts violently with many substances

Metal catches fire: smother with dry sand, anhydrous sodium carbonate or mineral absorbent (e.g. cat litter). Spilt on the floor, bench, etc.: scoop up as much metal as possible into a dry container. Cover the area with dry sand or anhydrous sodium carbonate and scoop into a dry bucket for further treatment. Rinse the area with plenty of water and mop.


APPARATUSAND

MATERIALS LIST

Chemistry

[CODE]SPECIMEN


2018



Practical Booklet A


146

Advice for centres

• All chemicals used should be at least laboratory reagent specification and labelled with appropriate safety symbols, e.g. irritant.

• For centres running multiple sessions – candidates for the later session should be supplied with clean, dry glassware. If it is not feasible then glassware from the first session should be thoroughly washed, rinsed with deionised water and allowed to drain.

• Ensure all chemicals are in date otherwise expected observations may not be seen.


147

Each candidate must be supplied with safety goggles or glasses.

Question 1


• one 50 cm3 burette of at least class B quality

• a funnel for filling the burette

• a retort stand and clamp



• a measuring cylinder of 100 cm3 capacity

• one 25 cm3 pipette of at least class B quality

• a safety pipette filler

• two conical flasks of 250 cm3 capacity

• a white tile or white paper

• a wash bottle containing deionised/distilled water

• 150 cm3 of 0.20 M potassium manganate(VII) labelled 0.20 M and irritant

• 150 cm3 of sodium ethandioate solution in a stoppered reagent bottle or beaker labelled sodium ethandioate and toxic. This solution should contain 62 gdm-3 of sodium ethandioate.

• 80 cm3 of 2 M dilute sulfuric acid in a stoppered reagent bottle or beaker labelled sulfuric acid portions and corrosive

Question 2


• six test tubes


• a spatula

• a dropping pipette

• deionised/distilled water

• 2 g of iron(II) sulfate labelled iron compound and irritant

• 10 cm3 of 1 M dilute sodium hydroxide solution labelled sodium hydroxide solution and corrosive


148

• 10 cm3 of 2 M dilute ammonia solution labelled dilute ammonia solution and irritant

• 10 cm3 of 0.2 M barium chloride solution labelled barium chloride solution and irritant

• 0 cm3 of 0.2 M silver nitrate solution labelled silver nitrate solution and irritant

Question 3

Test tubes and measuring cylinder used in previous questions could be re-used in this question. If not six test tubes have been recommended. Although a burette and pipette are not listed below they could be used from question 1.

• six test tubes

• one 100 cm3 measuring cylinder

• one 25 cm3 measuring cylinder


• 40 cm3 of 5 M copper(II) sulfate solution labelled X

• 20 cm3 of 2 M copper(II) sulfate solution labelled Y

Question 4

• two capillary tubes

• one ignition tube a third filled with propanone

• one TLC plate to fit a 250 cm3 beaker

• a pair of scissors or scissors to be made available to groups of candidates

• one 250 cm3 beaker with a lid which can be of any design e.g. cardboard

• a container of iodine crystals which will fit a TLC plate

• 20 cm3 of ethanol labelled ethanol and flammable

• Z is a mixture of a crystal/grain of benzoic acid mixed with a crystal/grain of naphthalene


149

Question 5

Test tubes used in previous questions could be re-used in this question. If not six test tubes have been recommended.

• six test tubes


• 20 cm3 of 0.2 M copper(II) sulfate solution labelled copper(II) sulfate solution and irritant

• 20 cm3 of 0.2 M ammonia solution labelled ligand 1 solution and irritant

• 20 cm3 of 0.2 M ethylene diamine solution labelled ligand 2 solution and irritant

• 20 cm3 of 0.2 M edta (disodium salt) solution labelled ligand 3 solution and irritant

A23 Chemistry Practical Risk Assessment

Question 1

Chemical Notes Emergency actionSulfuric acid(2 M)

Low hazard Even at this low concentration it may still cause harmin the eyes or in a cut.

In the eye: flood the eye with gently-running tap water for 10 minutes. See a doctor.Swallowed: do no more than wash out the mouth with water. Do not induce vomiting. Sips of water may help cool the throat and help keep the airway open. See a doctor.Spilt on the skin or clothing: remove contaminated clothing. Especially with concentrated acid, quickly use a dry cloth or paper towel to wipe as much liquid as possible off the skin. Then drench the skin with plenty of water. If a large area is affected or blistering occurs, see a doctor.Spilt on the floor, bench, etc.: wipe up small amounts with a damp cloth and rinse it well. For larger amounts, and especially for (moderately) concentrated acid, cover with mineral absorbent (e.g. cat litter) and scoop into a bucket. Neutralise with sodium carbonate. Rinse with plenty of water.

Sodium ethandioate

Soluble salts of oxalic acid (e.g. sodium and potassium) are as hazardous as the acid.

In the eye: flood the eye with gently-running tap water for 10 minutes. See a doctor if pain persists.Swallowed: do no more than wash out the mouth with water. Do not induce vomiting. Sips of water may help cool the throat and help keep the airway open. See a doctor.Spilt on the skin or clothing: remove contaminated clothing. Then drench the skin with plenty of water.Spilt on the floor, bench, etc.: wipe up small amounts with a damp cloth and rinse it well. For large spills, cover with mineral absorbent (e.g. cat litter) and scoop into a bucket. Rinse with plenty of water.


150

Potassium manganate(VII)

It is harmful if swallowed and stains the hands and clothing. Many hazardous reactions occur with reducing agents or concentrated acids

In the eye: flood the eye with gently-running tap water for at least 10 minutes. See a doctor.Swallowed: do no more than wash out the mouth with water. Do not induce vomiting. Sips of water may help cool the throat and help keep the airway open. See a doctor.Spilt on the skin or clothing: remove contaminated clothing and rinse it. Wash off the skin with plenty of water.Manganate(VII) will give permanent stains to clothing and the skin. If skin contamination is more than small, see a doctor.Spilt on the floor, bench, etc.: wear eye protection and gloves. Scoop up the solid. Rinse the area with water and wipe up.

Question 2

Chemical Notes Emergency actionIron(II) sulfate

Harmful if swallowed.

In the eye: flood the eye with gently-running tap water for at least 10 minutes. See a doctor.Swallowed: do no more than wash out the mouth with water. Do not induce vomiting. Sips of water may help cool the throat and help keep the airway open. See a doctor.Dust breathed in: remove the casualty to fresh air. See a doctor if breathing is difficult.Spilt on the skin or clothing: remove contaminated clothing and rinse it. Wash off the skin with plenty of water.Spilt on the floor, bench, etc.: scoop up solid (take care not to raise dust). Wipe up small solution spills or any traces of solid with cloth; for larger spills use mineral absorbent (e.g. cat litter).

Barium chlorideSolution

Low hazard In the eye: flood the eye with gently-running tap water for at least 10 minutes. See a doctor.Swallowed: do no more than wash out the mouth with water. Do not induce vomiting. Sips of water may help cool the throat and help keep the airway open. See a doctor.Spilt on the skin or clothing: brush off any solid. Remove contaminated clothing. Drench the skin with plenty of water. If a large area is affected or blistering occurs, see a doctor. Rinse contaminated clothing with water.Spilt on the floor, bench, etc.: rinse the area with water, diluting greatly. Solutions should be treated with mineral absorbent (e.g. cat litter).

Sodium hydroxide solution

It causes severe burns; it is particularly dangerous to the eyes.

In the eye: flood the eye with gently-running tap water for at least 20 minutes. See a doctor. If a visit to hospital is necessary, continue washing the eye during the journey in an ambulance.Swallowed: do no more than wash out the mouth with water. Do not induce vomiting. Sips of water may help cool the throat and help keep the airway open. See a doctor.Spilt on the skin or clothing: remove contaminated clothing. Drench the skin with plenty of water. If a large area is affected or blistering occurs, see a doctor.Spilt on the floor, bench, etc.: wipe up small amounts with a damp cloth and rinse it well. For larger amounts, and especially for (moderately) concentrated solutions, cover with mineral absorbent (e.g. cat litter) and scoop into a bucket. Neutralise with citric acid. Rinse with plenty of water.


151

Chemical Notes Emergency actionDilute Ammonia solution

It may still cause harm in eyes or in a cut.

Low hazard

In the eye: flood the eye with gently-running tap water for at least 20 minutes (for alkalis). See a doctor. If it is necessary to go to hospital, continue washing the eye during the journey in an ambulance.Vapour breathed in: remove the casualty to fresh air. Call a doctor if breathing is difficult.Swallowed: do no more than wash out the mouth with water. Do not induce vomiting. Sips of water may help cool the throat and help keep the airway open. See a doctor.Spilt on the skin or clothing: remove contaminated clothing. Drench the skin with plenty of water. If a large area is affected or blistering occurs, see a doctor.Spilt on the floor, bench, etc.: if large amounts are spilt and especially for (moderately) concentrated solutions. Cover with mineral absorbent (e.g. cat litter) and scoop into a bucket. Neutralise with citric acid. Rinse with plenty of water. Wipe up small amounts with a damp cloth and rinse it well.

Silver nitrate solution

Very dilute solutions are adequate for most school work whentesting for halides in solution.

In the eye: flood the eye with gently-running tap water for at least 10 minutes. See a doctor.Swallowed: do no more than wash out the mouth with water. Do not induce vomiting. Sips of water may help cool the throat and help keep the airway open. See a doctor.Spilt on the skin or clothing: remove contaminated clothing and rinse it. Wash off the skin with plenty of water. If the silver nitrate produces more than small burns, see a doctor.Spilt on the floor, bench, etc.: wear eye protection and gloves. Scoop up the solid. Rinse the area with water and wipe up, rinsing repeatedly. Rinse the mop or cloth thoroughly.

Question 3

Copper(II) sulfateSolution

Harmful if swallowed; the solid may irritate the eyes and skin

In the eye: flood the eye with gently-running tap water for at least 10 minutes. See a doctor.Swallowed: do no more than wash out the mouth with water. Do not induce vomiting. Sips of water may help cool the throat and help keep the airway open. See a doctor.Dust breathed in: remove the casualty to fresh air. See a doctor if breathing is difficult.Spilt on the skin or clothing: remove contaminated clothing and rinse it. Wash off the skin with plenty of water.Spilt on the floor, bench, etc.: scoop up solid (take care not to raise dust). Wipe up small solution spills or any traces of solid with cloth; for larger spills use mineral absorbent (e.g. cat litter).


152

Question 4

Chemical Notes Emergency actionIodine It is harmful

if breathed in or by contact with the skin. It causesburns to the skin if left for some time.

In the eye: flood the eye with gently-running tap water for 10 minutes. See a doctor.Vapour breathed in: remove the casualty to fresh air. Call a doctor if breathing is even slightly affected.Swallowed: do no more than wash out the mouth with water. Do not induce vomiting. Sips of water may help cool the throat and help keep the airway open. See a doctor.Spilt on the skin or clothing: brush off solid iodine and immerse in sodium thiosulfate solution (20%, 1 M). Remove contaminated clothing, soak it and drench the skin with plenty of water. See a doctor if a large area is affected or blistering occurs.Spilt on the floor, bench, etc.: scoop up any solid iodine, add sodium thiosulfate solution (20%, 1 M) to the remaining spill and leave for 1 hour. Mop up and rinse with plenty of water.

Propanone There is a serious risk of the liquid catching fire.Its vapour may catch fire above -20°C.It can cause severe eye damage and will degrease the skin.

In the eye: flood the eye with gently-running tap water for 10 minutes. See a doctor.Vapour breathed in: remove the casualty to fresh air. Keep him/her warm. See a doctor if breathing is difficult.Swallowed: do no more than wash out the mouth with water. Do not induce vomiting. Sips of water may help cool the throat and help keep the airway open. See a doctor.Clothing catches fire: smother flames on clothing or the skin with a fire blanket or other material. Cool any burnt skin with gently-running tap water for 10 minutes.Other propanone fires: allow fires in sinks, etc. to burn out. Fires at the top of test tubes, beakers, etc. should be smothered with a damp cloth or heat-proof mat.Spilt on the skin or clothing: remove contaminated clothing. If more than a test-tube amount was involved, wash the affected area and clothing with plenty of water.Spilt on the floor, bench, etc.: put out all Bunsen-burner flames. Wipe up small amounts with a cloth and rinse it well. For larger amounts, open all windows, cover with mineral absorbent (e.g. cat litter), scoop into a bucket and add water.


153

Chemical Notes Emergency actionEthanol There is a

serious risk of liquid catching fire; its vapour may catchfire above 13°C. The vapour / air mixture is explosive (from3.3 to 19% ethanol). Breathing vapour may result in sleepiness:

In the eye: flood the eye with gently-running tap water for 10 minutes. See a doctor.Swallowed: do no more than wash out the mouth with water. Do not induce vomiting. Sips of water may help cool the throat and help keep the airway open. See a doctor. NB: The casualty may show signs ofdrunkenness.Spilt on the skin or clothing: remove contaminated clothing and rinse it. Wash the affected area and clothing with plenty of water.Clothing catches fire: smother flames on clothing or the skin with a fire blanket or other material. Cool any burnt skin with gently-running tap water for 10 minutes.Other ethanol fires: allow fires in sinks, etc. to burn out. Fires at the top of test tubes, beakers, etc. should be smothered with a damp cloth or heat-proof mat.Spilt on the floor, bench, etc.: extinguish all Bunsen-burner flames. Wipe up small amounts with a cloth and rinse it well. For larger amounts, open all windows, cover with mineral absorbent (e.g. cat litter), scoop into a bucket and add water.

Question 5

Chemical Notes Emergency actionDilute Ammonia solution

It may still cause harm in eyes or in a cut.

Low hazard

In the eye: flood the eye with gently-running tap water for at least 20 minutes (for alkalis). See a doctor. If it is necessary to go to hospital, continue washing the eye during the journey in an ambulance.Vapour breathed in: remove the casualty to fresh air. Call a doctor if breathing is difficult.Swallowed: do no more than wash out the mouth with water. Do not induce vomiting. Sips of water may help cool the throat and help keep the airway open. See a doctor.Spilt on the skin or clothing: remove contaminated clothing. Drench the skin with plenty of water. If a large area is affected or blistering occurs, see a doctor.Spilt on the floor, bench, etc.: if large amounts are spilt andespecially for (moderately) concentrated solutions. Cover with mineral absorbent (e.g. cat litter) and scoop into a bucket. Neutralise with citric acid. Rinse with plenty of water. Wipe up small amounts with a damp cloth and rinse it well.


154

Chemical Notes Emergency actionEthylene diamine solution

CLEAPSS hazard sheet not available

Treat as hazardous as ammonia

In the eye: flood the eye with gently-running tap water for at least 20 minutes (for alkalis). See a doctor. If it is necessary to go to hospital, continue washing the eye during the journey in an ambulance.Vapour breathed in: remove the casualty to fresh air. Call a doctor if breathing is difficult.Swallowed: do no more than wash out the mouth with water. Do not induce vomiting. Sips of water may help cool the throat and help keep the airway open. See a doctor.Spilt on the skin or clothing: remove contaminated clothing. Drench the skin with plenty of water. If a large area is affected or blistering occurs, see a doctor.Spilt on the floor, bench, etc.: if large amounts are spilt andespecially for (moderately) concentrated solutions. Cover with mineral absorbent (e.g. cat litter) and scoop into a bucket. Neutralise with citric acid. Rinse with plenty of water. Wipe up small amounts with a damp cloth and rinse it well.

Chemical Notes EmergencyEDTA CLEAPSS

hazard sheet not available

Treat as hazardous as ammonia

In the eye: flood the eye with gently-running tap water for at least 20 minutes (for alkalis). See a doctor. If it is necessary to go to hospital, continue washing the eye during the journey in an ambulance.Swallowed: do no more than wash out the mouth with water. Do not induce vomiting. Sips of water may help cool the throat and help keep the airway open. See a doctor.Spilt on the skin or clothing: remove contaminated clothing. Drench the skin with plenty of water. If a large area is affected or blistering occurs, see a doctor.Spilt on the floor, bench, etc.: if large amounts are spilt andespecially for (moderately) concentrated solutions. Cover with mineral absorbent (e.g. cat litter) and scoop into a bucket. Neutralise with citric acid. Rinse with plenty of water. Wipe up small amounts with a damp cloth and rinse it well.


MARK SCHEME

155

DIVIDER FRONT


156

MARK SCHEME

DIVIDER BACK


General Certificate of Education

GENERAL MARKING INSTRUCTIONS

Chemistry


General Marking Instructions

IntroductionThe main purpose of the mark scheme is to ensure that examinations are marked accurately, consistently and fairly. The mark scheme provides examiners with an indication of the nature and range of candidates’ responses likely to be worthy of credit. It also sets out the criteria which they should apply in allocating marks to candidates’ responses.

Assessment objectivesBelow are the assessment objectives for GCE Chemistry:

Candidates should be able to:

AO1 Demonstrate knowledge and understanding of scientific ideas, processes, techniques and procedures.

AO2 Apply knowledge and understanding of scientific ideas, processes, techniques and procedures:• in a theoretical context • in a practical context • when handling quantitative and qualitative data

AO3 Analyse, interpret and evaluate scientific information, ideas and evidence (in relation to particular issues)• make judgements and reach conclusions • develop and refine practical design and procedures

Quality of candidates’ responsesIn marking the examination papers, examiners should be looking for a quality of response reflecting the level of maturity which may reasonably be expected of a 17 or 18-year-old which is the age at which the majority of candidates sit their GCE examinations.

Flexibility in markingMark schemes are not intended to be totally prescriptive. No mark scheme can cover all the responses which candidates may produce. In the event of unanticipated answers, examiners are expected to use their professional judgement to assess the validity of answers. If an answer is particularly problematic, then examiners should seek the guidance of the Supervising Examiner.

Positive markingExaminers are encouraged to be positive in their marking, giving appropriate credit for what candidates know, understand and can do rather than penalising candidates for errors or omissions. The exception to this for GCE Chemistry is when Examiners are marking complex calculations and mechanisms when the Examiners are briefed to mark by error or omission. Examiners should make use of the whole of the available mark range for any particular question and be prepared to award full marks for a response which is as good as might reasonably be expected of a 17 or 18-year-old GCE candidate.

Awarding zero marksMarks should only be awarded for valid responses and no marks should be awarded for an answer which is completely incorrect or inappropriate.


Marking CalculationsIn marking answers involving calculations, examiners should apply the ‘carry error through’ rule so that candidates are not penalised more than once for a computational error. To avoid a candidate being penalised, marks can be awarded where correct conclusions or inferences are made from their incorrect calculations.

Types of mark schemesMark schemes for tasks or questions which require candidates to respond in extended written form are marked on the basis of levels of response which take account of the quality of written communication.

Other questions which require only short answers are marked on a point for point basis with marks awarded for each valid piece of information provided.

Levels of responseIn deciding which level of response to award, examiners should look for the number of indicative content points in candidate responses to ensure that the answer has been written to coincide with the question. In deciding which mark within a particular level to award to any response, quality of communication will be assessed and examiners are expected to use their professional judgement.

The following guidance is provided to assist examiners.

• Threshold performance: Response which just merits inclusion in the level but the quality of communication is basic should be awarded a mark at the bottom of the range.

• High performance: Response which fully satisfies the level description for both content and quality of communication should be awarded a mark at the top of the range.

Quality of written communicationQuality of written communication is taken into account in assessing candidates’ responses to all tasks and questions on theory examination papers that require them to respond in extended written form. These tasks and questions are marked on the basis of levels of response. The description for each level of response includes reference to the quality of written communication.

For conciseness, quality of written communication is distinguished within levels of response as follows:

Level C: Quality of written communication is basic.Level B: Quality of written communication is good.Level A: Quality of written communication is excellent.

In interpreting these level descriptions, examiners should refer to the more detailed guidance provided below:

Level C (Basic): Basic reference to scientific terminology. The candidate makes only a limited selection and use of an appropriate form and style of writing. The organisation of material may lack clarity and coherence. There is little use of specialist vocabulary. Presentation, spelling, punctuation and grammar may be such that intended meaning is not clear.


Level B (Good): Good reference to scientific terminology. The candidate makes a reasonable selection and use of an appropriate form and style of writing. Relevant material is organised with some clarity and coherence. There is some use of appropriate specialist vocabulary. Presentation, spelling, punctuation and grammar are sufficiently competent to make meaning clear.

Level A (Excellent): Excellent reference to scientific terminology. The candidate successfully selects and uses the most appropriate form and style of writing. Relevant material is organised with a high degree of clarity and coherence. There is widespread and accurate use of appropriate specialist vocabulary. Presentation, spelling, punctuation and grammar are of a sufficiently high standard to make meaning clear.


MARK SCHEME

Chemistry

[CODE]SPECIMEN


2017

Assessment Unit AS 1assessing

Basic Concepts in Physical and Inorganic Chemistry

161

MARKSCHEME


162

AVAILABLE MARKS

/ denotes alternative points

Section A

1 B [1]

2 C [1]

3 D [1]

4 A [1]

5 B [1] 6 A [1]

7 D [1]

8 A [1]

9 A [1]

10 C [1]

Total for Section A 10


163

AVAILABLE MARKS

Section B

11 (a) (i) a region within an atom that can hold up to two electrons with opposite spin [1]

(ii)

[1]

(iii) 1s2 2s2 2p6 3s2 3p6 3d10 4s1 [1]

(b) (i) all 8 ionisation energies showing an increase [1] biggest increase is between 6th and 7th ionisation energy [1] [2]

(ii) O+ (g) → O2+ (g) + e− [1]

(iii) O has smaller nuclear charge/one less proton [1] outer electron is in the same shell so the shielding is similar [1] less nuclear attraction on outermost electron in O [1] [3]

(c) going down the group the ionisation energy decreases [1] the outermost electron is further from the nucleus [1] the outermost electron experiences less shielding [1] outer electron is attracted more strongly to the nucleus [1] [4]

12 (a) layers of positive ions [1] sea of delocalised electrons [1] [2] (b) (i) atoms of the same element [1] U235 has 143 neutrons U238 has 146 [1] [2] (ii) 237.979 = 235 x + 238 (100-x) /100 23797.9 = 235x + 23800 – 238 x x = abundance of U235 = 0.7%; U238 = 99.3% [3]

(c) (i) UF4 + 2Mg → U + 2MgF2 [2]

(ii) UO2 + 4HF → UF4 + 2H2O [2]

(iii) +6 [1] +6 [1] +4 [1] [3]

(d) (i) nitrogen(IV) oxide [1]

(ii) relights glowing splint [1]

13

16


164

AVAILABLE MARKS

13 (a) weak forces/van der Waals’ forces between layers [1] layers can slide /slip off [1] [2] (b) strong covalent bonds [1] 3d/giant tetrahedron [1] [2]

(c) no free charge carriers/free electrons/all electrons in covalent bonds [1]

14 (a) (i) moles = 0.287/143.4 = 0.002 ratio 1:1 0.002 107.9 = 0.216 g error -1 [2]

(ii) Ag+ + e → Ag [1]

(b) Cu+ + Cl → Cu2+ + Cl– [1]

(c) (i) oxidation number of copper changes from +2 to +1 = reduction [1] oxidation number of copper changes from 0 to +1 = oxidation [1] oxidation and reduction of the same species (copper) in the same reaction [1] [3]

(ii) it is insoluble [1]

(d) moles of copper chloride = 2.0/134.5 = 0.01487 ratio 2HCl : 1 CuCl2 0.029747 = vol 1.0 /1000 volume = 29.7 cm3 = 30 cm3 to 2 sig figures error -1 [3]

5

11


AVAILABLE MARKS

165

15 (a) (i) Cl2 + 3F2 → 2ClF3 [1]

(ii) the electrostatic attraction between a shared pair of electrons and the nuclei of the bonded atoms [2]

(iii)

[2]

(b) (i)

trigonal bipyramid [1] bent/v/nonlinear [1]

five bonding pairs of electrons repel each other equally [1]

two bonding pairs of electrons and two lone pairs of electrons; the lone pairs of electrons repel more than bonding pairs [1] [6]

(ii) 104.5° [1]

(c) (i) I+ Cl– [1]

chlorine is more electronegative than iodine [1] [2]

(ii) chlorine has van der Waals’ forces between molecules [1] iodine monochloride has permanent dipole-dipole attractions between molecules [1] permanent dipole-dipole attractions are stronger/intermolecular forces stronger in ICl [1] more energy needed to break the stronger intermolecular force [1] [4]

FClF

F xx xx

xxx

[1]

As

F

F

FF

F[1]

Cl

F F

+

18


166

AVAILABLE MARKS

AVAILABLE MARKS

16 (a) add dilute acid and effervescence for carbonate [1] flame test yellow/orange for sodium ions [1] add silver nitrate solution and ppt forms for halide [1] dissolve in water [1] [4]

(b) (i) Indicative content• in sodium strong attraction between positive ions and delocalised electrons• in sodium metallic bonding• in sodium chloride strong attraction between positive ion and negative ion• ionic bonding• in iodine weak van der Waals forces between molecules • ionic bonding is stronger than metallic bonding which is stronger than van der Waals [6]

Band Response Mark

A

Candidates must use appropriate specialist terms to fully explain the difference in melting point using a minimum of 6 points of indicative content. They must use good spelling, punctuation and grammar and the form and style are of an excellent standard.

[5]–[6]

B

Candidates must use appropriate specialist terms to explain the difference in melting point using a minimum of 4 points of indicative content. They must use satisfactory spelling, punctuation and grammar and the form and style are of a good standard.

[3]–[4]

C

Candidates explain partially the difference in melting point using a minimum of 2 points of indicative content. They use limited correct spelling, punctuation and grammar and the form and style is of a basic standard.

[1]–[2]

D Response not worthy of credit. [0]

(ii) grey – black [1] white [1] [2]

(c) 3I2 + 6NaOH → NaIO3 + 5NaI + 3H2O [2]

(d) (i) 46 40 = 1840 g 1840/ 149.9 = 12.3 M [2]

(ii) from colourless to yellow/brown [1]

Total for Section B

Paper Total

17

80

90


MARKSCHEME

Chemistry

[CODE]SPECIMEN


2017



167

Chemistry



MARKSCHEME


168

AVAILABLE MARKS


Section A

1 C [1]

2 A [1]

3 A [1]

4 B [1]

5 B [1] 6 A [1]

7 C [1]

8 C [1]

9 D [1]

10 B [1]



169

AVAILABLE MARKS

Section B

11

element moles ratio

C 22.2 ÷ 12 = 1.85 2

H 3.7 ÷ 1 = 3.70 4

Br 74.1 ÷ 80 = 0.93 1

moles [1] empirical Formula = C2H4Br [1] 216 ÷ 108 = 2 molecular Formula = C4H8Br2 [1] [3] 12 (a) CH3CH(CH3)CH2CH3 [1] 2-methylbutane [1]

CH3C(CH3)2CH3 [1] 2,2-dimethylpropane [1] [4]

(b) molecules which have the same molecular formula but a different structural formula. [2]

(c) neopentane [1] increased branching [1] weaker van der Waals forces [1] [3]

(d) C5H12 8O2 → 5CO2 6H2O unbalanced [1] balanced [1] [2]

(e) initiation Cl2 → 2Cl • [1] propagation Cl • 1 C5H12 → C5H11 • 1 HCl [1] C5H11 • 1 Cl2 → C5H11Cl 1 Cl • [1] termination Cl • 1 Cl • → Cl2 [1] or C5H11 • 1 C5H11 • → C10H22 or C5H11 • 1 Cl • → C5H11Cl [4]

3

15


170

AVAILABLE MARKS

13 (a) (i) enthalpy change(s) [1] is/are independent of the route taken [1] [2]

(ii) enthalpy change which occurs when 1 mole of a substance [1] undergoes complete combustion in oxygen [1] under standard conditions. [1] [3]

(iii) (–394) (–286 2) ( 75) [1] –891 kJ mol–1 [1] [2]

(b) (i) average bond enthalpies are used [1]

(ii) –698 = 4(C–H) – 2346 4(C–H) = 1648 412 kJ mol–1

error -1 [3]

(c) (i) Indicative content• measure mass of spirit burner containing ethanol before and after burning• measure out known volume of water into a calorimeter using a burette• burn the ethanol in the spirit burner and use the heat evolved to heat the water in the calorimeter• measure initial and final temperature of water (after heating) using a thermometer• calculate the heat evolved using the equation q = mc∆T• calculate the number of moles of ethanol used from the mass of ethanol burned• divide the heat evolved by the moles of ethanol used to calculate the enthalpy of combustion [6]

(ii) incomplete combustion [1] heat loss to surroundings [1] [2]

Band Response Mark

A

Candidates must use appropriate specialist terms to explain fully the process of determining the enthalpy of combustion (using a minimum of 6 points of indicative content). They use good spelling, punctuation and grammar and the form and style are of an excellent standard.

[5]–[6]

B

Candidates must use appropriate specialist terms to explain the process of determining the enthalpy of combustion (using a minimum of 5 points of indicative content). They use good spelling, punctuation and grammar and the form and style are of a good standard.

[3]–[4]

C

Candidates explain briefly and partially the process of determining the enthalpy of combustion (using a minimum of 4 points of indicative content). They use limited spelling, punctuation and grammar and the form and style are of a basic standard.

[1]–[2]



171

AVAILABLE MARKS

AVAILABLE MARKS

14 (a) peak shifts to right and peak is lower [2] other drawing errors [–1] [2]

(b) number of molecules with energy greater than Ea [1] increases [1] [2]

(c) catalyst provides an alternative route [1] of lower activation energy Ea [1] more molecules have energy greater than Ea [1] number/frequency of successful collisions (between SO2 and O2 molecules) increases [1] [4]

15 (a) (i) the H atom in HBr has a + charge [1] which is attracted to area of high electron density (in double bond) [1] [2]

(ii)

[3]

curly arrows drawn correctly [1] error -1 [4]

8

CH2 = CH2 CH2 – CH2CH2 – CH2

H+ H ..

+

H

Br− Br−

Br

Number ofmolecules

with agiven energy

EnergyEa

© CCEA


172

AVAILABLE MARKS

(b) (i)

CH3 – CH2 CH3

CH3 HC C

Z isomer [1]

CH3 – CH2 H

CH3 CH3

C C

E isomer [1] [2]

(ii)

CH3

Br

CH3CH2CCH2CH3

major [1]

CH3

Br

CH3CH2CHCHCH3

minor [1] [2]

(iii) carbocation intermediates produced [1] tertiary carbocation more stable than secondary carbocation [1] tertiary carbocation leads to formation of major product [1] [3]

(c) (i) C4H9Br + NaOH → C4H9OH + HBr [2]

(ii) secondary [1] carbon bonded to –OH is bonded to two other carbon atoms [1] [2]

(d) (i) C4H9Br + NaOH → C4H8 + NaBr + H2O [2]

(ii) in ethanol [1]

(iii) elimination [1]

(iv) but-2-ene [1] 22


173

AVAILABLE MARKS

16 (a) rate of forward reaction = Rate of reverse reaction [1] the amount of any given reactant or product remains constant [1] [2]

(b) increase [1] 3 moles (g) LHS 2 moles (g) RHS equilibrium shifts to RHS to oppose the change [1] [2]

(c) decrease [1] (forward) reaction is exothermic equilibrium shifts to LHS to oppose the change/cool the system [1] [2]

(d) no effect on yield [1] increases the rate of the forward and reverse reactions equally [1] [2]

(e) (i) Kc = [NO2]2/[NO]2[O2] [1]

mol–1 dm3 [1] [2]

(ii) Kc > 1 [1]

(f) 4 × 46 2 × 148 = 184/296 = 62.2%

error -1 [2]

Total for Section B Paper Total

13

80

90


BLANK PAGE


MARK SCHEME

Chemistry

[CODE]SPECIMEN


2017


Basic Practical ChemistryPractical Booklet A

175

MARKSCHEME


176

AVAILABLE MARKS


1 (a) white [1]

(b) two different particle sizes are seen [1] different shades of white [1] [2]

(c) (i) no change at the start, possible vapour in the middle, (colourless) liquid at the end (any 2 out of 3) [2]

(ii) colourless, green colour (pH 7) [1]

(d) (i) fizzing/frothing/foaming/effervescence[1] white solid left/some solid disappears [1] [2]

(ii) limewater goes milky [1]

(e) (i) measuring cylinder [1] 25 cm3 indicates an accuracy of 1 cm3 [1] [2] (ii) titre value/cm3 [2] value of titration 20 cm3 +/– 2 cm3 = [2] +/– 4 cm3 = [1] correct recording of values, e.g. decimal places and calculation of titre [2] [6]

(f) brick red [1]

2 (a) X:sodiumfloats;nogas[1] Y:sodiumfloats;lotsofgasproduced[1] Z:sodiumfloats;notmuchgas[1] [3]

(b) Y contains ethanol, fastest reaction [1]

3 (a) substance melts darkens/goes black black solid left/ (most)disappears error -1 [2]

(b) black solid (carbon) forms [1]

Total for Booklet A

18

4

25

3


MARK SCHEME

Chemistry

[CODE]SPECIMEN


2017


Basic Practical ChemistryPractical Booklet B

177

MARKSCHEME


178

AVAILABLE MARKS

178

AVAILABLE MARKS


1 (a) changes from green to red [2]

(b) changes from green to red and there is some brown (bromine) present [2]

2 add water and stir to dissolve [1] filterthemixture[1] add hydrochloric acid to the solid [1] itfizzesshowingitisacarbonate[1] filterthesolutionandaddasolublesulfate[1] white precipitate produced [1] toamaximumof[4] [4]

3 (a) sketch of apparatus ie gas passing through water/alkali [2] explanationofhowitworks[1] [3]

(b) acts as a catalyst for the reaction [1]

(c) thespeedofdropsofliquidreturningtotheflaskwouldincreasewith vigorousrefluxing [1]

(d) a similar boiling point to the 1-chlorobutane [1]

(e) water [1]

(f) place in separating funnel with, e.g. water [1] stopper the funnel [1] invert the funnel [1] shake and allow the liquids to separate and remove the lower one [1] [4]

(g) used to dry the 1-chlorobutane [1] anhydrous sodium sulfate [1] [2]

(h) (i) gcm-3 [1] 0.81 23 = 18.63 g [1] [2]

(ii) 18.63/74=0.25mol;0.25molofC4H9Cl = 0.25 × 92.5 = 23.1 g [2]

(i) boiling points are usually measured in ranges [1] a range of 1/2 degrees is the usual range [1] the range is increased to collect as much as possible (if there are no interfering compounds) [1] [3]

(j) compare the pure and “impure” spectra [1] the“impure”spectrumwillhaveextrapeaks[1] [2]

4

4

22


179

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179

4 (a) M(s) + H2O(g)→MO(s)+H2(g) equation [1] state symbols [1] [2]

(b) same mass [1] same particle size [1] 100% purity [1] [3]

(c) (i) steam is diluted water or because steam is a gas and reacts more slowly than water or despite the higher temperature steam is less concentrated than water or it’s like bromine and chlorine, chlorine is more reactive but it’s a gas [1]

(ii) bubbles/fizzingeffervescence[1] white solid [1] calcium moves up and down [1] heat produced [1] steam produced [1] calcium dissolves/disappears [1] toamaximumof[3] [3]

(d) (i) time/seconds or minutes [1] volume of hydrogen gas/cm3 [1] [2]

(ii) steeper at the start [1] earlierhorizontalfinish[1] [2]

(iii) allow gas to go into a test tube [1] lighted splint [1] pop noise [1] [3]

(e) 3.4gofCa=3.4/40=0.085mol;0.085×24dm3 = 2.04 = 2.0 dm3 [4] error -1

(f) theGrouptwometalsareveryreactivewithoxygen[1] hencetheexperimentwouldbeoververyquickly[1] need to slow down the reaction [1] onlywayistodilutetheoxygen[1] e.g.bymixingitwithnitrogen/noblegas[1] collecttheoxygenoverwater/inasyringe[1] comparetheratesofoxygencollectionandrelate to reactivity [1] toamaximumof[5] [5]

Total for Booklet B

25

55


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MARKSCHEME

181


2018

Chemistry

[CODE]SPECIMEN

Assessment Unit A2 1assessing

Further Physical and Organic Chemistry


182

AVAILABLE MARKS


Section A

1 B [1]

2 D [1]

3 C [1]

4 A [1]

5 B [1] 6 C [1]

7 D [1]

8 D [1]

9 B [1]

10 D [1]



183

AVAILABLE MARKS

Section B

11 (a) (i) H⦵ = ∑ fH⦵ (products) – ∑fH⦵ (reactants) = [3 × −393.5] – [2 × −824.2] = 467.9 kJ mol−1 [2]

S⦵ = ∑ S⦵ (products) − ∑ S⦵ (reactants) = [(4 × 27.3) + (3 × 213.6)] − [(2 × 87.4) + (3 × 5.7)] = 558.1 J K−1 mol-1 [2]

G⦵ = H⦵ − TS⦵

= 467.9 − (298 × 0.5581) = 301.6 kJ mol−1 [1]

(ii) G⦵ is positive [1]

(b) T = (H⦵ ÷ S⦵) = (467.9 ÷ 0.5581) = 838K [2]

12 (a) the energy required to convert 1 mole [1] of an ionic solid into gaseous ions [1] [2]

(b) (i)

[4]

(ii) LE = (+1123) + (150) + (736) + (1450) + (2 79) + (2 –348) = 2921 kJ mol–1 [2]

8

Mg+(g) + e− + F2(g)

Mg2+(g) + 2F−(g)

Mg(s) + F2(g)

MgF2(s)

↑

↑

↑

↑↑

↑

↓

[1]

[1]

[1]

[1]


184

AVAILABLE MARKS

(c) (i)

[2]

(ii) LE = (–155) – [(–1920) + (2 –364)] = 2493 kJ mol–1 [2]

13 (a) (i) 2-hydroxy-2-methylbutanenitrile [2]

(ii) optical [1]

(iii)

correct 3D representation [1] mirror image [1] [2]

(iv) nucleophilic addition [1]

(v)

error –1 [4]

(vi) the carbonyl group is planar [1] the nucleophile attacks from both sides to an equal extent [1] equal amounts of each optical isomer formed [1] [3]

(b) heat [1] with either acidified potassium dichromate, Tollens’ reagent or Fehling’s solution [1] correct positive result with butanal, no change with butanone [1] [3]

H

Mg2+

[1] [1]F−

O O

O

OH

H

HH

H

H H

12

C

CH3

CN

HO

H5C2

CH3

C

NC

OH

C2H5

O

OHH+−O

C

C C

C2H5

C2H5

CH3CH3

CH3CH3

C2H5

C2H5

CN

CN CN

CN−

C

−O


185

AVAILABLE MARKS

AVAILABLE MARKS

(c)

[2] (ii) Indicative content

• yellow/orange• solid• capillary tube• heat slowly• record the temperature when the solid melts• compare to tables of data [6]

Band Response Mark

A

Candidates must use appropriate specialist terms to explain fully the process of identifying the ketone (using a minimum of 6 points of indicative content). They use good spelling, punctuation and grammar and the form and style are of an excellent standard.

[5]–[6]

B

Candidates must use appropriate specialist terms to explain the process of identifying the ketone (using a minimum of 5 points of indicative content). They use good spelling, punctuation and grammar and the form and style are of a good standard.

[3]–[4]

C

Candidates explain briefly and partially the process of identifying the ketone (using a minimum of 4 points of indicative content). They use limited spelling, punctuation and grammar and the form and style are of a basic standard.

[1]–[2]

D Response not worthy of credit. [0] 24

14 (a) (i) Ka = [CH3CH2COO−][H+]

[CH3CH2COOH] [1] (ii) Ka = [H+]2 ÷ [CH3CH2COOH] [1] [H+] = 0.00184 [1] pH = 2.74 [1] [3]

(iii) a solution which minimises changes in pH [1] on addition of small amounts of acid or alkali [1] [2]

(iv) moles of acid 0.25 × 0.3 = 0.075 moles of salt 0.15 × 0.2 = 0.03 (concentration of acid = 0.15 mol dm–3) (concentration of salt = 0.06 mol dm–3) [H+] = Ka × ([acid]/[salt]) = 3.38 × 10–5 mol dm–3) pH = 4.47 [4]

H H

C C

CH3 CH3

+H2OCH3CH2 CH3CH2

NO2

NO2 NN NO2

NO2

O + NH2N


186

AVAILABLE MARKS

AVAILABLE MARKS

(b) (i) CH3CH2COOH + NaOH → CH3CH2COONa + H2O [1]

(ii) phenolphthalein [1] colourless to pink [2] range matches the vertical portion of the titration curve [1] [4]

(iii) moles of NaOH = 0.20 × (18.5/1000) = 0.0037 moles of CH3CH2COOH = 0.0037 concentration of CH3CH2COOH = 0.148 mol dm–3 [3]

(iv) [H+] = Kw ÷ [OH–] = 5 × 10–14 mol dm–3 [1] pH = 13.30 [1] [2]

15 (a)

before after [2]

(b) (i) HNO3 + 2H2SO4 → NO2

+ + H3O+ + 2HSO4

– [2]

(ii) nitronium ion [1]

(iii) electrophilic substitution

error –1 [5]

(iv) methyl 3-nitrobenzoate [1]

(v) cream solid [1]

16 (a) first [1] valid explanation [1] [2]

(b) zero [1] valid explanation [1] [2]

20

OCH3OCH3

OCH3OCH3

+

C C

C

H

H

C

+ H+NO2NO2

NO2NO2

O O

OO

12

© CCEA


187

AVAILABLE MARKS

AVAILABLE MARKS

(c) rate = k[C4H9Br] [1]

(d) 2000 [1] s–1 [1] [2]

(e)

error –1 [5]

17 (a) (i)

[1]

(ii) propane-1,2,3-triol [1]

(iii)

[1]

CH3 CH3

CH3CH3

CH3CH3

CH3CH3

H3C H3C

H3C H3C

RDS

OH−

OH

Br −BrC

CC+

C+

12

OH

OH

OH

H

H

H

H

H

C

C

C

(CH2)7 ─ CH = CHCH2CH = CH(CH2)4CH3



O

O

O

O

O

O

H

H

H

H

H

C

C

C C

C

C


188

AVAILABLE MARKS

(b) (i) 3-methylbutananoic aicd methanol [1]

(ii)

[2]

(iii) Indicative content• acid and alcohol into round-bottomed flask and add concentrated sulfuric acid slowly• add anti-bumping granules • heat under reflux• distill and collect at boiling point of ester• shake with aqueous sodium carbonate and release pressure• separate ester layer using separating funnel• add a named drying agent• decant/filter [6]

Band Response Mark

A

Candidates must use appropriate specialist terms to explain fully the preparation of the ester (using a minimum of 6 points of indicative content). They use good spelling, punctuation and grammar and the form and style are of an excellent standard.

[5]–[6]

B

Candidates must use appropriate specialist terms to explain the preparation of the ester (using a minimum of 5 points of indicative content). They use good spelling, punctuation and grammar and the form and style are of a good standard.

[3]–[4]

C

Candidates explain briefly and partially the preparation of the ester (using a minimum of 4 points of indicative content). They use limited spelling, punctuation and grammar and the form and style are of a basic standard.

[1]–[2]

D Response not worthy of credit. [0] 12

Total for Section B

Total

CH3 ─ C ─ CH2COOH + CH3OH CH3 ─ C ─ CH2COOCH3 + H2O

CH3

H H

CH3

100

110


MARKSCHEME

189


2018

Chemistry

[CODE]SPECIMEN


Analytical, Transition Metals, Electrochemistry

and Organic Nitrogen Chemistry


190

AVAILABLE MARKS


Section A

1 D [1]

2 A [1]

3 C [1]

4 C [1]

5 D [1] 6 C [1]

7 B [1]

8 C [1]

9 D [1]

10 B [1]



191

AVAILABLE MARKS

Section B

11 (a) anode 2H2 + 4OH– → 4H2O + 4e– [1] cathode O2 + 2H2O + 4e– → 4OH– [1] [2]

(b) 2H2(g) + O2(g) → 2H2O(l) [2]

(c) advantages: renewable source of electricity/does not produce pollution/silent [2]

12 (a) dipolar ions [1] strong attraction between opposite charges [1] [2]

(b) 2H2NCH(CH2SeH)COOH + Na2CO3 → 2H2NCH(CH2SeH)COONa + H2O + CO2 [2]

(c) (i) H2N-CH(CH2SeH)-CO-NH-CH(CH2SeH)-COOH [3]

(ii) induced fit mechanism lowers activation energy [1]

(iii) bell shaped curve and labelled axes [2]

13 (a) (i) Zn + 2Fe3+ ↔ 2Fe2+ + Zn2+ [1]

(ii) E = +0.32V so reaction should proceed [1]

(b) (i) MnO4– + 5Fe2+ + 8H+ → Mn2+ + 4H2O + 5Fe3+ [1]

(ii) moles MnO4– = 26.0 10–3 0.02 = 0.52 10–3

moles Fe = 5 0.52 10–3 = 2.6 10–3 in 25 cm3

= 2.6 10–2 in 250 cm3

mass Fe = 2.6 10–2 56 = 1.456 g % Fe = 1.456 100 = 91% 1.60 error - [1] [4]

(iii) colourless to pink [2]

14 (a) (i) nucleophilic substitution [1]

(ii) C4H9Br + NH3 → C4H9NH2 + HBr [1] δ+ δ– (iii) C–Br polarised lone pair on N/NH3 attracted to Cδ +

C–N bond formed, C–Br bond broken [3]

(b) (i) lithal [1]

(ii) C3H7CN + 4[H] → C3H7CH2NH2 [2]

6

10

9


192

AVAILABLE MARKS

(c) C6H5NO2 + 6[H] → C6H5NH2 + 2H2O [2] (d) (i) less basic than the others [1]

+ (ii) C6H5NH2 + HCl → C6H5NH3 Cl– [1]

(iii) phenylethyl group attached to N atom which has two hydrogens [1] + (e) (i) C6H5-N ≡ N [2]

(ii) sodium nitrite and dilute hydrochloric acid [1]

(iii) A HCl/H2SO4 or NaOH [1] B lithal [1] C HNO2/NaNO2 + HCl [1] D PCl5/HCl [1]

15 (a) transition metal ions have an incomplete d shell [1]

(b) (i) VO2+(aq) blue [1] V3+(aq) green [1] [2]

(ii) 3VO2+ + Cr + 6H+ → 3VO2+ + Cr3+ + 3H2O [2]

emf = 1.74 V [1] [3]

(c) (i) blue [1] yellow [1] [2]

(ii) octahedral [1]

(iii) hydrochloric acid/sodium chloride [1]

(d) (i) H2N-CH2-CH2-NH2 [1]

(ii) two coordinate bonds/points of attachment [1]

(iii) [Ni(en)3]2+ [2]

(e) (i) Co(CH3COO)2.4H2O [2]

(ii) to oxidise cobalt(II) to cobalt(III) [2]

(iii) octahedral [1]

(iv) six [1]

(v) 1 dm3 of H2O2 produces 20 dm3 of oxygen 20/24 mole of oxygen = 0.833 i.e. 0.833 mol dm–3

2:1 ratio therefore 1.67 mol dm–3

error - [1] [3]

20


193

AVAILABLE MARKS

AVAILABLE MARKS

16 (a) (i) same molecular formula but different structural formula [2]

(ii) HCOOH + C2H5OH HCOOC2H5 + H2O [2]

(iii) add conc. H2SO4/methanoic acid/ethanol [1] remove water [1] [2] (b) (i) Tetramethylsilane, Si(CH3)4 [2]

(ii) Indicative content• HCOO – singlet – next to O• CH2 – quartet – next to 3H• CH3 – triplet – next to 2H• ratio 1:2:3• area under curve is proportional to the number of H in each environment• greatest deshielding• H next to O [6]

Band Response Mark

A

Candidates must use appropriate specialist terms to explain fully the process of nmr (using a minimum of 6 points of indicative content). They use good spelling, punctuation and grammar and the form and style are of an excellent standard.

[5]–[6]

B

Candidates must use appropriate specialist terms to explain the process of nmr (using a minimum of 5 points of indicative content). They use good spelling, punctuation and grammar and the form and style are of a good standard.

[3]–[4]

C

Candidates explain briefly and partially the process of nmr (using a minimum of 4 points of indicative content). They use limited spelling, punctuation and grammar and the form and style are of a basic standard.

[1]–[2]


(c) 28 C2H4+ or CO+ [1]

45 HCOO+ or C2H5O+ [1] [2]

(d) (i) bonds in molecules vibrate absorb energy of a certain frequency dependent on the atoms mass in the bond -OH absorption peak for propanoic acid different positions for C=O and C=O | | OH O

allow any 4 from the above 5 statements [4]GCE_CHEM_SAM_V.2 UPDATED_12.10.16

194

AVAILABLE MARKS

AVAILABLE MARKS (ii) sodium carbonate [1]

effervescence with the acid [1] [2]

17 (a) C7H6O3 + C4H6O3 → C9H8O4 + C2H4O2 [2]

(b) aspirin is not very soluble in water. [1]

(c) Indicative content• TLC plate, pencil line, mark 3 spots• dissolve small amounts of ‘crude’ aspirin, ‘purified’ aspirin and ‘pure’(commercial) aspirin in separate test tubes in a suitable solvent, e.g. ethanol• spot each sample on to the TLC plate• place in developing tank with a suitable solvent, e.g. ethyl ethanoate• remove plate and mark the position of solvent front• use UV light or a locating reagent [6]

Band Response Mark

A

Candidates must use appropriate specialist terms to explain fully the process of TLC (using a minimum of 5 points of indicative content). They use good spelling, punctuation and grammar and the form and style are of an excellent standard.

[5]–[6]

B

Candidates must use appropriate specialist terms to explain the process of TLC (using a minimum of 4 points of indicative content). They use good spelling, punctuation and grammar and the form and style are of a good standard.

[3]–[4]

C

Candidates explain briefly and partially the process of TLC (using a minimum of 3 points of indicative content). They use limited spelling, punctuation and grammar and the form and style are of a basic standard.

[1]–[2]


(d) cost or volatility [1]

Total for Section B

Total

22

10

100

110


MARKSCHEME

195

MARKSCHEME


2018

Chemistry

[CODE]SPECIMEN



Practical Booklet A


196

AVAILABLE MARKS


1 (a) use of starting values to one decimal place [1] correct calculation of average titre [2] rough value between 23.4 and 25.2 [1] accuracy of titration value +/- 0.2 cm3 of 23.2 cm3 sliding scale for [2] [6]

(b) read the bottom of the meniscus or allow a method taking into account the colour of the potassium manganate(VII) [2]

(c) colourless to pink [2]

2 (a) green [1]

(b) green solution [1]

(c) green precipitate [1]

(d) green precipitate [1]

(e) white precipitate [1]

(f) no reaction [1]

(g) iron(II) sulfate [1]

3 (a) the comparison of colours would be made by placing test tubes of the solutions side by side until one colour exactly matched the other colour in intensity/depth [2] explanation/description of how the 5M solution would have to be appropriately diluted with the correct use of suitable apparatus, e.g. measuring cylinders [2] [4]

(b) 2M [1]

4 (a) correct labelling of solvent front and starting point [1] two spots labelled with appropriate sizes at approximately correct places [1] solvent front near the top of the TLC slide [1] [3]

(b) two substances [1]

10

7

5

4


197

AVAILABLE MARKS

5 Ligand 1 is ammonia solution ligand 2 is ethylene diamine solution ligand 3 is edta solution all of the ligands will form a blue complex; ligand 3 will displace ligand 2 which will displace ligand 1. In each case for a positive result there should be an appropriate colour change. For a negative result there is no change based on the original colour of the solutions. Hence 3 positive results and 3 negative results. –[1] for each incorrect result [4]

Total for Booklet A

4

30


BLANK PAGE


199

MARKSCHEME


2018

Chemistry

[CODE]SPECIMEN



Practical Booklet B


200

AVAILABLE MARKS


1 (a) retention time [1] e.g. detection signal [1] [2]

(b) 4 [1]

(c) 15/28 100 = 53.6% [2]

2 (a) green [1] and blue [1] solids [2]

(b) (i) iron(II) hydroxide [1] green [1] [2]

(ii) Cu(NH3)42+ [1]

deep blue [1] [2]

(iii) add a solution of barium chloride [1] white precipitate produced [1] [2]

3 (a) it forms the hydrochloride/salt [1] which is ionic and thus more soluble [1] [2]

(b) the phenyl diazonium ion [1] is unstable at higher temperatures [1] [2]

(c) iodine reacts with the starch [1] to produce a blue-black colour [1] [2]

(d) it contains an ionic group [1] which is solvated by water [1] the benzene ring is only a relatively small part of the structure [1] any 2 from 3 [2]

(e) turn down [1] the amount of water flowing through the water pump [1] [2]

(f) it removes the ethanoic acid [1] which has a high/higher boiling point/more difficult to evaporate [1] [2]

(g) (seal) a capillary tube at one end and put in some azo compound [1] place in an oil bath/melting point apparatus [1] heat slowly [1] note when the solid starts to melt [1] note when the solid stops melting [1] [5]

5

8


201

AVAILABLE MARKS

AVAILABLE MARKS

(h) 5 g of phenylamine = 5/93 = 0.054 mol 7 g of naphthol = 7/144 = 0.0486 = 0.049 mol

RMM of diazo compound is 200.5 0.049 mol = 0.049 200.5 = 9.82 g

% yield = 3/9.82 100 = 30.5498 = 30.5 depending on the numbers presented in the calculation [5] error –[1]

decimal place incorrect –[1] use of phenylamine –[1] [5]

4 (a) (i) flask containing water + nitramide [1] possible mechanism for adding the water/nitramide [1] means of collecting the nitrous oxide [1] possible water bath for constant temperature [1] explanation how the experiment is carried out i.e. measuring volume per unit time [2] to a maximum of 5 marks [5]

(ii) temperature [1]

(iii) e.g. there are too many bubbles to count/not all the bubbles are the same size [1]

(iv) lone pair on the nitrogen (or oxygen) [1] forms hydrogen bonds [1] [2]

(b) (i) the point at 1500 seconds [1] the volume should be 16.8 cm3 [1] [2]

(ii) 11.2/24000 = 0.00047 = 0.0005 mol of N2O; hence % decomposed = 0.0005/0.05 100 = 1% [3]

(iii) 5 10–6 mol dm–3 s–1 = k 0.5 mol dm–3 k = 10–5 [1] s–1 [1] [2]

(c) (i) step one involves the separation of a positive charge from a negative charge which takes energy; a negative ion produced from a negative ion involves repulsion. Hence step one is rate determining [2] or nitramide is the only reactant in the rate equation

(ii) the reactive intermediate is NO2NH– [1]

(iii) the reactive intermediate needs to be formed in step 1 [1] then it needs to be used up in step 2 [1] [2]

(d) (i) heat with sodium hydroxide solution [1] test gas given off with conc hydrochloric acid[1] white smoke [1] [3]

(ii) heat with alkali, ammonium salt produces ammonia [1]

Total for Booklet B

22

25

60


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ccea gce specimen assessment material for chemistry · 2019-09-19 · for first teaching from...

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