aqa-chm5-w-qp-jun07

Surname Centre Number Candidate Signature

Other Names Candidate Number

For Examiners Use

General Certificate of Education June 2007 Advanced Level Examination CHEMISTRY CHM5 Unit 5 Thermodynamics and Further Inorganic Chemistry Monday 25 June 2007 9.00 am to 11.00 am

For this paper you must have G a calculator.

For Examiners Use Question Mark Question Mark

Time allowed: 2 hours Instructions G Use blue or black ink or ball-point pen. G Fill in the boxes at the top of this page. G Answer all questions in Section A and Section B in the spaces provided. All working must be shown. G Do all rough work in this book. Cross through any work you do not want to be marked. G The Periodic Table/Data Sheet is provided on pages 3 and 4. Detach this perforated sheet at the start of the examination. G Section B questions are provided on a perforated sheet. Detach this sheet at the start of the examination. Information G The maximum mark for this paper is 120. G Mark allocations are shown in brackets. G This paper carries 20 per cent of the total marks for Advanced Level. G You are expected to use a calculator where appropriate. G Your answers to the questions in Section B should be written in continuous prose, where appropriate. You will be assessed on your ability to use an appropriate form and style of writing, to organise relevant information clearly and coherently, and to use specialist vocabulary, where appropriate. Advice G You are advised to spend about 1 hour on Section A and about 1 hour on Section B.

1 2 3 4 5 6 7 8

Total (Column 1) Total (Column 2) TOTAL

Examiners Initials

APW/Jun07/CHM5

CHM5

2 SECTION A Answer all questions in the spaces provided.

LEAVE MARGIN BLANK

1 Consider the incomplete BornHaber cycle and the table of data below.

Mg2 (g) + 2Cl (g)

+

Mg(s) + Cl2(g)

MgCl2(s) Name of standard enthalpy change Enthalpy of atomisation Enthalpy of atomisation Enthalpy of formation First ionisation enthalpy Electron affinity Enthalpy of lattice formation Substance to which enthalpy change refers chlorine magnesium magnesium chloride magnesium chlorine magnesium chloride Value of enthalpy change / kJ mol1 +121 +150 642 +736 364 2493

(a) Complete the Born-Haber cycle above by writing the appropriate chemical formulae, with state symbols, on the dotted lines. (4 marks) (b) Use the cycle and the values given in the table to calculate the second ionisation enthalpy of magnesium. ............................................................................................................................................. ............................................................................................................................................. ............................................................................................................................................. ............................................................................................................................................. (3 marks)APW/Jun07/CHM5

The Periodic Table of the Elements

APW/Jun07/CHM5

I

The atomic numbers and approximate relative atomic masses shown in the table are for use in the examination unless stated otherwise in an individual question.

I

II

III

IV

V

VI

VII4.0

0HeHelium

1.0

H6.9 10.8 12.0 14.0 16.0

Hydrogen

Key19.0

1 6.9

9.0

LiLithium Boron Carbon

Be3 27.0 28.1 5 6 7 31.0

relative atomic mass Li B C NNitrogen

2 20.2

OOxygen

FFluorine

NeNeon

Lithium

Beryllium

3

4

atomic number AlAluminium

8 32.1

9 35.5

10 39.9

23.0

24.3

Na Si52.0 54.9 55.8 58.9 58.7 63.5 65.4 13 69.7 14 72.6

Mg

PPhosphorus

SSulphur

ClChlorine

ArArgon

Sodium

Magnesium

Silicon

11

12

39.1

40.1

45.0

47.9

50.9

15 74.9

16 79.0

17 79.9

18 83.8

KChromium Manganese Iron Cobalt Nickel Copper Zinc

Ca24 95.9 98.9 101.1 102.9 106.4 107.9 112.4 25 26 27 28 29 30 31 114.8

Sc

Ti

V

Cr

Mn

Fe

Co

Ni

Cu

Zn

GaGallium

GeGermanium

AsArsenic

SeSelenium

BrBromine

KrKrypton

Potassium

Calcium

Scandium

Titanium

Vanadium

3

19

20

21

22

23

32 118.7

33 121.8

34 127.6

35 126.9

36 131.3

85.5

87.6

88.9

91.2

92.9

RbMolybdenum Technetium Ruthenium Rhodium Palladium Silver

Sr42 183.9 186.2 190.2 192.2 195.1 197.0 43 44 45 46 47 48 200.6

Y

Zr

Nb

Mo

Tc

Ru

Rh

Pd

Ag

CdCadmium

InIndium

SnTin

SbAntimony

TeTellurium

IIodine

XeXenon

Rubidium

Strontium

Yttrium

Zirconium

Niobium

37

38

39

40

41

49 204.4

50 207.2

51 209.0

52 210.0

53 210.0

54 222.0

132.9

137.3

138.9

178.5

180.9

CsTungsten Rhenium Osmium Iridium Platinum Gold

Ba74 75 76 77 78 79

La

Hf

Ta

W

Re

Os

Ir

Pt

Au80

HgMercury

TlThallium

PbLead

BiBismuth

PoPolonium

AtAstatine

RnRadon

Caesium

Barium

Lanthanum

Hafnium

Tantalum

55

56

57

223.0

226.0

227

*

72

73

81

82

83

84

85

86

Fr

Ra

Ac

Francium

Radium

Actinium

87 140.9 144.2 144.9 150.4

88

89

152.0 157.3 158.9 162.5 164.9 167.3 168.9 173.0 175.0

140.1

* 58 7159 231.0 238.0 237.0 60 61 62

Lanthanides PaProtactinium Uranium

Ce

Pr

Nd

Pm

Sm63 239.1

EuEuropium

GdGadolinium

TbTerbium

DyDysprosium

HoHolmium

ErErbium

TmThulium

YbYtterbium

LuLutetium

Cerium

Praseodymium Neodymium Promethium Samarium

58

64 243.1 247.1

65 247.1

66 252.1

67 (252)

68 (257)

69 (258)

70 (259)

71 (260)

232.0

90 103 Actinides91 92 93

Th

U

NpNeptunium

PuPlutonium

AmAmericium

CmCurium

Bk94 95 96 97 98

Cf99

EsBerkelium Californium Einsteinium

FmFermium

MdMendelevium

NoNobelium

LrLawrencium

Thorium

90

100

101

102

103

4

Gas constant R = 8.31 J K1 mol1

Table 1 Proton n.m.r chemical shift data Type of proton RCH3 R2CH2 R3CH RCOCH3 ROCH3 RCOOCH3 ROH /ppm 0.71.2 1.21.4 1.41.6 2.12.6 3.13.9 3.74.1 0.55.0

Table 2 Infra-red absorption data Bond CH CC C C C O Wavenumber/cm1 28503300 7501100 16201680 16801750 10001300 32303550 25003000

CO OH (alcohols) OH (acids)

APW/Jun07/CHM5

5 (c) The standard enthalpies of hydration of the Mg2+ and the Cl ions are 1920 kJ mol1 and 364 kJ mol1, respectively. Use this information and data from the table in part (a) to calculate the enthalpy of solution of magnesium chloride. ............................................................................................................................................. ............................................................................................................................................. ............................................................................................................................................. ............................................................................................................................................. ............................................................................................................................................. ............................................................................................................................................. (3 marks) (d) The standard enthalpy of solution of ammonium chloride, NH+Cl, is +15 kJ mol1. 4 (i) Explain why ammonium chloride dissolves spontaneously in water even though this process is endothermic. ................................................................................................................................... ................................................................................................................................... ................................................................................................................................... ................................................................................................................................... (2 marks) (ii) A 2.0 g sample of ammonium chloride is dissolved in 50 g of water. Both substances are initially at 20 C. Calculate the temperature change and the final temperature of the solution. Assume that the specific heat capacity of the solution is 4.2 J K1 g1. Temperature change ................................................................................................. ................................................................................................................................... ................................................................................................................................... ................................................................................................................................... ................................................................................................................................... ................................................................................................................................... Final temperature of solution ................................................................................... (5 marks) Turn overAPW/Jun07/CHM5

LEAVE MARGIN BLANK

17

6 2 Data for the following reaction, which represents the reduction of aluminium oxide by carbon, are shown in the table below. Al2O3(s) + 3C(s) 2Al(s) + 3CO(g) Substance Al2O3(s) C(s) Al(s) CO(g) Hf / kJ mol1 1669 0 0 111 S / J K1 mol1 51 6 28 198

LEAVE MARGIN BLANK

(a) Calculate the values of H , S and G for the above reaction at 298 K and suggest why this reaction is not feasible at 298 K. H ..................................................................................................................................... ............................................................................................................................................. ............................................................................................................................................. ............................................................................................................................................. ............................................................................................................................................. S ...................................................................................................................................... ............................................................................................................................................. ............................................................................................................................................. G ..................................................................................................................................... ............................................................................................................................................. ............................................................................................................................................. Reason why this reaction is not feasible at 298 K ............................................................. ............................................................................................................................................. (8 marks)

APW/Jun07/CHM5

7 (b) Calculate the temperature above which this reaction is feasible. (If you have been unable to calculate values for H and S in part (a) you may assume that they are +906 kJ mol1 and +394 J K1 mol1 respectively. These are not the correct values.) ............................................................................................................................................. ............................................................................................................................................. ............................................................................................................................................. ............................................................................................................................................. (2 marks) (c) The reaction between aluminium oxide and carbon to form aluminium and carbon monoxide does not occur to a significant extent until the temperature reaches a value about 1000 K above that of the answer to part (b). Give one reason for this. ............................................................................................................................................. (1 mark) (d) State the method used to reduce aluminium oxide on an industrial scale. Give the essential conditions for this industrial process. Method ............................................................................................................................... Conditions .......................................................................................................................... ............................................................................................................................................. ............................................................................................................................................. (3 marks)

LEAVE MARGIN BLANK

14

Turn overAPW/Jun07/CHM5

8 3 The table below shows some standard electrode potentials. E /V Fe3+(aq) + e Fe2+(aq) Cr3+(aq) + e Cr2+(aq) Fe2+(aq) + 2e Fe(s) Zn2+(aq) + 2e Zn(s) Cr2+(aq) + 2e Cr(s) + 0.77 0.41 0.44 0.76 0.91

LEAVE MARGIN BLANK

(a) Predict the products, if any, when the following substances are mixed. In each case use E values from the table to explain your answer. (i) iron metal with aqueous zinc(II) ions Products, if any ......................................................................................................... Explanation .............................................................................................................. ................................................................................................................................... (ii) aqueous iron(III) ions with aqueous chromium(II) ions Products, if any ......................................................................................................... Explanation .............................................................................................................. ................................................................................................................................... (5 marks) (b) Calculate the e.m.f. of the following standard cell and deduce an equation for the overall cell reaction. Zn(s)|Zn2+(aq)||Cr3+(aq),Cr2+(aq)|Pt e.m.f. ................................................................................................................................... Equation ............................................................................................................................. (2 marks)

APW/Jun07/CHM5

9 (c) Chromium(III) ions are weakly acidic in aqueous solution as shown by the following equation. [Cr(H2O)6]3+(aq) [Cr(H2O)5(OH)]2+(aq) + H+(aq)

LEAVE MARGIN BLANK

The value of Ka for this reaction is 1.15 104 mol dm3. Calculate the pH of a 0.500 mol dm3 solution of [Cr(H2O)6]3+(aq). ............................................................................................................................................. ............................................................................................................................................. ............................................................................................................................................. ............................................................................................................................................. ............................................................................................................................................. ............................................................................................................................................. (5 marks) (d) State what you would observe after addition of the following reagents to separate aqueous solutions containing [Cr(H2O)6]3+ ions. In each case give the formula of the chromium-containing product. (i) an excess of NaOH(aq) Observation(s) .......................................................................................................... ................................................................................................................................... Formula of product ................................................................................................... (ii) Na2CO3(aq) Observation(s) .......................................................................................................... ................................................................................................................................... Formula of product ................................................................................................... (5 marks)

17

Turn overAPW/Jun07/CHM5

10 4 (a) Give the meaning of the term electronegativity. ............................................................................................................................................. ............................................................................................................................................. (2 marks) (b) State and explain the trend in electronegativity across Period 3 from Na to Cl. Trend .................................................................................................................................. Explanation ........................................................................................................................ ............................................................................................................................................. (3 marks) (c) (i) Name the main type of bonding in each of the oxides MgO and P4O10 Bonding in MgO ....................................................................................................... Bonding in P4O10 ..................................................................................................... (ii) Explain how the type of bonding in P4O10 can be predicted by a consideration of electronegativity. ................................................................................................................................... ................................................................................................................................... (3 marks) (d) Write equations for the reaction of Na2O and of SO2 with water. Equation for Na2O ............................................................................................................. Equation for SO2 ................................................................................................................ (2 marks) (e) Write an equation for the reaction of MgO with dilute hydrochloric acid. ............................................................................................................................................. (1 mark) (f) Write an equation for the reaction of P4O10 with an excess of aqueous sodium hydroxide. ............................................................................................................................................. ............................................................................................................................................. (1 mark)

LEAVE MARGIN BLANK

12APW/Jun07/CHM5

11 SECTION B Detach this perforated sheet. Answer all questions in the spaces provided on pages 13 to 20 of this booklet.

LEAVE MARGIN BLANK

5

(a) Explain why the ester methyl ethanoate has a lower boiling point than its isomer, propanoic acid. (2 marks) (b) A polyester is formed when ethane-1,2-diol reacts with butanedioic acid. Draw the structure of the repeating unit of this polymer. Suggest why this polyester begins to melt at a higher temperature than poly(ethene) which has molecules of a similar size to those in the polyester. (4 marks) (c) Outline a mechanism for the formation of an ester by the reaction between ethanoyl chloride and an alcohol. (4 marks) (d) The ester ethyl ethanoate is hydrolysed when it is heated with water in the presence of an acid catalyst. An equilibrium is established. CH3COOCH2CH3(l) + H2O(l) CH3COOH(l) + CH3CH2OH(l)

A 0.50 mol sample of ethyl ethanoate was heated with 4.0 mol of water. At equilibrium, 70 % of the ester was hydrolysed. Calculate a value of Kc for this reaction. (5 marks)

6 One characteristic property of transition metals is variable oxidation state. (a) For each of the following processes, write two equations to show how the transition metal catalyst reacts and is reformed. Identify the different oxidation states shown by the transition metal catalyst in each process. (i) the Contact Process catalysed by vanadium(V) oxide (ii) the oxidation of ethanedioate ions by acidified potassium manganate(VII), autocatalysed by Mn2+(aq) ions. (6 marks) (b) Cobalt(II) ions cannot easily be oxidised to cobalt(III) ions in water. Suggest why this oxidation can be carried out in aqueous ammonia and identify a suitable oxidising agent. (3 marks) (c) Metal ions Q2+ in acidified aqueous solution can be oxidised by aqueous potassium dichromate(VI). In a titration, an acidified 25.0 cm3 sample of a 0.140 mol dm3 solution of Q2+(aq) required 29.2 cm3 of a 0.040 mol dm3 solution of potassium dichromate(VI) for complete reaction. Determine the oxidation state of the metal Q after reaction with the potassium dichromate(VI). (6 marks) Turn overAPW/Jun07/CHM5

12 7 The reaction scheme below shows a two-stage synthesis of ethane-1,2-diamine, H2NCH2CH2NH2. Reaction 1 H2C = CH2 BrCH2CH2Br Reaction 2 H2NCH2CH2NH2

LEAVE MARGIN BLANK

(a) Suggest a reagent for Reaction 1. Name and outline a mechanism for this reaction. (5 marks) (b) Suggest a reagent for Reaction 2. Name the type of mechanism involved and write an equation for the overall reaction. (3 marks) (c) Draw the structure of the complex ion formed when aqueous cobalt(II) ions react with an excess of ethane-1,2-diamine. (2 marks) (d) Ethane-1,2-diamine can be converted into the EDTA4 ion shown below. OOCCH2 NCH2CH2N OOCCH2 CH2COO CH2COO4

State why this ion can act as a multidentate ligand. Write an equation for the reaction of EDTA4 with aqueous cobalt(II) ions. In your equation represent the ligand by EDTA4 Explain why the EDTA4 ion readily displaces unidentate ligands such as water. (5 marks)

8

(a) The compounds CH3CH2Cl and CH3CHCl2 can be distinguished by comparing their proton n.m.r. spectra. For each compound, describe its proton n.m.r. spectrum by giving the number of peaks, the integration ratio and the splitting patterns. (6 marks) (b) The following pairs of compounds can be distinguished using the reagents indicated. Each compound is in a separate aqueous solution. For each one of the compounds, describe what you would observe and write equations for any reactions that occur. (i) KBr and KI using chlorine water (ii) BaCl2 and MgCl2 using dilute sulphuric acid (iii) CoCl2 and CuCl2 using concentrated hydrochloric acid (9 marks)

END OF QUESTIONSAPW/Jun07/CHM5

13 ............................................................................................................................................................... ............................................................................................................................................................... ............................................................................................................................................................... ............................................................................................................................................................... ............................................................................................................................................................... ............................................................................................................................................................... ............................................................................................................................................................... ............................................................................................................................................................... ............................................................................................................................................................... ............................................................................................................................................................... ............................................................................................................................................................... ............................................................................................................................................................... ............................................................................................................................................................... ............................................................................................................................................................... ............................................................................................................................................................... ............................................................................................................................................................... ............................................................................................................................................................... ............................................................................................................................................................... ............................................................................................................................................................... ............................................................................................................................................................... ............................................................................................................................................................... ............................................................................................................................................................... ............................................................................................................................................................... ............................................................................................................................................................... ............................................................................................................................................................... ............................................................................................................................................................... Turn overAPW/Jun07/CHM5

LEAVE MARGIN BLANK

14 ............................................................................................................................................................... ............................................................................................................................................................... ............................................................................................................................................................... ............................................................................................................................................................... ............................................................................................................................................................... ............................................................................................................................................................... ............................................................................................................................................................... ............................................................................................................................................................... ............................................................................................................................................................... ............................................................................................................................................................... ............................................................................................................................................................... ............................................................................................................................................................... ............................................................................................................................................................... ............................................................................................................................................................... ............................................................................................................................................................... ............................................................................................................................................................... ............................................................................................................................................................... ............................................................................................................................................................... ............................................................................................................................................................... ............................................................................................................................................................... ............................................................................................................................................................... ............................................................................................................................................................... ............................................................................................................................................................... ............................................................................................................................................................... ............................................................................................................................................................... ...............................................................................................................................................................

LEAVE MARGIN BLANK

APW/Jun07/CHM5


LEAVE MARGIN BLANK

16 ............................................................................................................................................................... ............................................................................................................................................................... ............................................................................................................................................................... ............................................................................................................................................................... ............................................................................................................................................................... ............................................................................................................................................................... ............................................................................................................................................................... ............................................................................................................................................................... ............................................................................................................................................................... ............................................................................................................................................................... ............................................................................................................................................................... ............................................................................................................................................................... ............................................................................................................................................................... ............................................................................................................................................................... ............................................................................................................................................................... ............................................................................................................................................................... ............................................................................................................................................................... ............................................................................................................................................................... ............................................................................................................................................................... ............................................................................................................................................................... ............................................................................................................................................................... ............................................................................................................................................................... ............................................................................................................................................................... ............................................................................................................................................................... ............................................................................................................................................................... ...............................................................................................................................................................

LEAVE MARGIN BLANK

APW/Jun07/CHM5


LEAVE MARGIN BLANK

18 ............................................................................................................................................................... ............................................................................................................................................................... ............................................................................................................................................................... ............................................................................................................................................................... ............................................................................................................................................................... ............................................................................................................................................................... ............................................................................................................................................................... ............................................................................................................................................................... ............................................................................................................................................................... ............................................................................................................................................................... ............................................................................................................................................................... ............................................................................................................................................................... ............................................................................................................................................................... ............................................................................................................................................................... ............................................................................................................................................................... ............................................................................................................................................................... ............................................................................................................................................................... ............................................................................................................................................................... ............................................................................................................................................................... ............................................................................................................................................................... ............................................................................................................................................................... ............................................................................................................................................................... ............................................................................................................................................................... ............................................................................................................................................................... ............................................................................................................................................................... ...............................................................................................................................................................

LEAVE MARGIN BLANK

APW/Jun07/CHM5


LEAVE MARGIN BLANK

20 ............................................................................................................................................................... ............................................................................................................................................................... ............................................................................................................................................................... ............................................................................................................................................................... ............................................................................................................................................................... ............................................................................................................................................................... ............................................................................................................................................................... ............................................................................................................................................................... ............................................................................................................................................................... ............................................................................................................................................................... ............................................................................................................................................................... ............................................................................................................................................................... ............................................................................................................................................................... ............................................................................................................................................................... ............................................................................................................................................................... ............................................................................................................................................................... ............................................................................................................................................................... ............................................................................................................................................................... ............................................................................................................................................................... ............................................................................................................................................................... ............................................................................................................................................................... ............................................................................................................................................................... ............................................................................................................................................................... ............................................................................................................................................................... ...............................................................................................................................................................

LEAVE MARGIN BLANK

Copyright 2007 AQA and its licensors. All rights reserved.

APW/Jun07/CHM5

aqa-chm5-w-qp-jun07

Documents

leave margin blank

potassium dichromate

aluminium oxide

k1 mol1

turn overapw jun07 chm5

perforated sheet

ammonium chloride

aqueous cobalt