*X012/701* X012/701 CHEMISTRY ADVANCED HIGHER. Reference may be made to the Chemistry Higher and Advanced Higher Data Booklet.

Transcription

1 X02/70 NTIONL QULIFITIONS 2008 FRIY, 30 MY 9.00 M.30 M EMISTRY VNE IGER Reference may be made to the hemistry igher and dvanced igher ata ooklet. SETION 40 marks Instructions for completion of SETION are given on page two. For this section of the examination you must use an pencil. SETION 60 marks ll questions should be attempted. nswers must be written clearly and legibly in ink. LI X02/70 6/8270 *X02/70*

2 SETION Read carefully heck that the answer sheet provided is for hemistry dvanced igher (Section ). 2 For this section of the examination you must use an pencil and, where necessary, an eraser. 3 heck that the answer sheet you have been given has your name, date of birth, SN (Scottish andidate Number) and entre Name printed on it. o not change any of these details. 4 If any of this information is wrong, tell the Invigilator immediately. 5 If this information is correct, print your name and seat number in the boxes provided. 6 The answer to each question is either,, or. ecide what your answer is, then, using your pencil, put a horizontal line in the space provided (see sample question below). 7 There is only one correct answer to each question. 8 ny rough working should be done on the question paper or the rough working sheet, not on your answer sheet. 9 t the end of the exam, put the answer sheet for Section inside the front cover of your answer book. Sample Question To show that the ink in a ball-pen consists of a mixture of dyes, the method of separation would be chromatography fractional distillation fractional crystallisation filtration. The correct answer is chromatography. The answer has been clearly marked in pencil with a horizontal line (see below). hanging an answer If you decide to change your answer, carefully erase your first answer and using your pencil, fill in the answer you want. The answer below has been changed to. [X02/70] Page two

3 . n atom has the electronic configuration s 2 2s 2 2p 6 3s 2 3p What is the charge of the most likely ion formed from this atom? The electronic configurations, X and Y, for two uncharged atoms of sodium are as follows. X s 2 2s 2 2p 6 3s Y s 2 2s 2 2p 6 4s Which of the following statements is true? X is an excited state. oth X and Y have vacant 2d orbitals. Energy is absorbed in changing Y to X. Less energy is required to ionise Y compared to X. 3. Lewis base may be regarded as a substance which is capable of donating an unshared pair of electrons to form a covalent bond. Which of the following could act as a Lewis base? o 3+ P 3 l 3 N Silicon can be converted into an n-type semiconductor by adding boron carbon arsenic aluminium. 5. Which of the following statements referring to the structures of sodium chloride and caesium chloride is correct? There are eight chloride ions surrounding each sodium ion. There are eight chloride ions surrounding each caesium ion. The chloride ions are arranged tetrahedrally round the sodium ions. The chloride ions are arranged tetrahedrally round the caesium ions. 6. The transition metal salts, MnF 2, FeF 2 and of 2, have identical crystal structures because the metal ions have similar radii similar colours the same nuclear charge the same number of d electrons. 7. Which of the following hydrides, when added to water, would give the most acidic solution? Sodium hydride Magnesium hydride Silicon hydride Sulphur hydride 8. Sodium hydride reacts with sodium sulphate as shown. 4Na + Na 2 SO 4 4NaO + Na 2 S This reaction demonstrates sodium hydride acting as a base an acid a reducing agent an oxidising agent. [Turn over [X02/70] Page three

4 9. Three elements, X, Y and Z, are in the same period of the Periodic Table. The oxide of X is amphoteric, the oxide of Y is basic and the oxide of Z is acidic. Which of the following shows the elements arranged in order of increasing atomic number? Y, X, Z Y, Z, X Z, X, Y X, Y, Z 3. 3 OO O 3 OO O The above reaction can be said to have reached equilibrium when the equilibrium constant K is equal to the reaction between the acid and the alcohol has stopped the concentrations of the products equal those of the reactants the rate of production of ethyl ethanoate equals its rate of hydrolysis. 0. Which of the following involves oxidation? MnO 4 MnO 4 2 g + [g(n 3 ) 2 ] + [Fe(N) 6 ] 4 [Fe(N) 6 ] 3 [Ni( 2 O) 6 ] 2+ [Ni(N) 4 ] 2. The number of unpaired electrons in a gaseous Ni 2+ ion is P + Q R + S t 298 K the equilibrium constant for this reaction is Which of the following is true? The value of S must be positive. The value of G must be positive. dding a catalyst will change the equilibrium constant. Increasing the concentration of P will not change the equilibrium constant. 4. When sulphur dioxide and oxygen react the following equilibrium is established. 2SO 2 (g) + O 2 (g) 2SO 3 (g) The equilibrium constant for the reaction is 3300 at 630 and 2 at 850. Which line in the table is correct for the reaction? cm 3 of mol l hydrochloric acid is mixed with 500 cm 3 of mol l sodium hydroxide solution. The p of the resulting solution will be Sign of Product yield as temperature increases + decreases + increases decreases increases 6. The ronsted-lowry definition of a base is a substance which acts as a proton donor to form a conjugate acid proton donor to form a conjugate base proton acceptor to form a conjugate acid proton acceptor to form a conjugate base. [X02/70] Page four

5 7. The mean bond enthalpy of the N bond is equal to one third of the value of for which change of the following changes? 2. V N 3 (g) N(g) + 3(g) 2N 3 (g) N 2 (g) (g) N 3 (g) N 2 (g) + 2 (g) 2 2 2N 3 (g) + O 2 (g) N 2 (g) O(g) 2 metal X salt bridge g 8. The entropy of a perfect crystal is zero at 0K 25 K 273 K 298 K. 9. Which of the following reactions results in a decrease in entropy? N 2 O 4 (g) 2NO 2 (g) N 2 (g) (g) 2N 3 (g) ao 3 (s) ao(s) + O 2 (g) (s) + 2 O(g) O(g) + 2 (g) 20. Which of the following is not a required condition for measuring standard electrode potentials? Volume of litre Temperature of 298K oncentration of mol l Pressure of atmosphere The E values are X 2+ (aq) + 2e X(s) g + (aq) + e g(s) E = V E = V In the above cell, which of the following is reduced? X(s) g(s) X 2+ (aq) g + (aq) 22. Under standard conditions, the emf of the cell would be mol l X 2+ (aq) mol l g + (aq) l(s) l 3+ (aq) u 2+ (aq) u(s). 34 V V V V. 23. For a cell in which the following reaction occurs X(s) + 2Y + (aq) X 2+ (aq) + 2Y(s) the E value is. 5 V. G for the reaction, per mole of X, is kJ mol 44. 8kJ mol kJ mol kJ mol. [Turn over [X02/70] Page five

6 24. d+ d- r r (step ) + r r _ r _ + r (step 2) r r The two steps in the reaction mechanism shown can be described as ethene acting as a nucleophile and r acting as a nucleophile ethene acting as a nucleophile and r acting as an electrophile ethene acting as an electrophile and r acting as a nucleophile ethene acting as an electrophile and r acting as an electrophile. 25. In the homologous series of alkanols, increase in chain length from 3 O to 0 2 O is accompanied by increased volatility and increased solubility in water increased volatility and decreased solubility in water decreased volatility and decreased solubility in water decreased volatility and increased solubility in water. 27. compound 3 8 O does not react with sodium and is not reduced by lithium aluminium hydride. It is likely to be an acid ether alcohol aldehyde. 28. Which of the following is least acidic? 3 O 26. Which of the following is not caused by hydrogen bonding? The low density of ice compared to water O O The solubility of methoxymethane in water The higher boiling point of methanol compared to ethane The higher melting point of hydrogen compared to helium O O O [X02/70] Page six

7 29. Which statement about ethanol and its isomeric ether is true? They have similar volatilities have similar infra-red spectra form the same products when burned in excess oxygen form the same products when reacted with acidified dichromate. 33. white crystalline compound, soluble in water, was found to react with both dilute hydrochloric acid and sodium hydroxide solution. Which of the following might it have been? 6 5 O 6 5 N OO 2 N 2 OO 30. When 2-bromobutane is reacted with potassium cyanide and the compound formed is hydrolysed with dilute acid, the final product is butanoic acid pentanoic acid 2-methylbutanoic acid 2-methylpropanoic acid. 3. Which of the following compounds would liberate one mole of hydrogen gas if one mole of it reacts with excess sodium? 2 5 O 3 O 3 OO O 2 2 O 34. Which of the following amines has the lowest boiling point? 4 9 N N N N( 3 ) Spectral studies of an organic compound indicated the presence of a di-substituted benzene ring, two methyl groups and a molecular weight of 34. Which of the following is a possible structure for the compound? Two isomeric esters, X and Y, have the molecular formula 4 8 O 2. Ester X on hydrolysis with sodium hydroxide solution gives 3 2 OONa, and ester Y on similar treatment gives 3 2 O. Which line in the table shows the correct names of X and Y? O 3 3 O 3 X Y propyl methanoate ethyl ethanoate 2 3 methyl propanoate methyl propanoate ethyl ethanoate ethyl methanoate O 3 propyl methanoate methyl propanoate 3 2 O [Turn over [X02/70] Page seven

8 36. Which of the following molecules does not exhibit optical isomerism? r r 39. n organic compound with empirical formula, 2 4 O, has major peaks at 75 cm and 3300 cm in its infrared spectrum. The structural formula of the compound could be 3 O 3 OO r r 3 OO OO. (O) 3 ro 37. Which of the following could not exist in isomeric forms? 2 F r 2 4 l Elemental analysis of an organic compound showed it contained 70. 6% carbon, 23. 5% oxygen and 5. 9% hydrogen by mass. The structural formula of the compound could be 2 2 OO O O 2 O 2 2 O [X02/70] Page eight

9 40. drug containing a carboxyl group can bind to an amino group on a receptor site in three different ways. ydrogen-bond acceptor ydrogen-bond donor Ionic interaction O O O O N O N 2 O N 3 binding site binding site binding site The drug with the following structure could bind to the same site O 3 only by ionic interaction only as a hydrogen-bond donor only as a hydrogen-bond acceptor both as a hydrogen-bond donor and acceptor. [EN OF SETION ] andidates are reminded that the answer sheet for Section MUST be placed INSIE the front cover of your answer book. [Turn over for SETION on Page ten [X02/70] Page nine

10 SETION 60 marks are available in this section of the paper. ll answers must be written clearly and legibly in ink.. (a) What is the arrangement of the electron pairs around the iodine atom in an IF 5 molecule? Marks (b) y considering the electron pairs, explain why the bond angle in F 3 is greater than the bond angle in NF 3. (2) 2. n aqueous solution of the compound [ol 2 (N 3 ) 4 ]l gave the following transmittance spectrum. Transmittance % wavelength/nm (a) From the above spectrum, deduce the colour of the solution. (b) The solution contains the complex ion [ol 2 (N 3 ) 4 ] +. (i) (ii) (iii) What is the oxidation number of cobalt in this complex ion? Name this complex ion. Write down the electronic configuration of cobalt in this complex ion in terms of s, p and d orbitals. (4) 3. Some metal salts emit light when heated in a unsen flame. Lithium nitrate changes the flame colour to crimson. Magnesium nitrate has no effect on the flame colour. (a) (b) (c) Explain, in terms of electrons, why some metal salts emit light when heated in a unsen flame. Suggest why magnesium nitrate has no effect on the flame colour. alculate the energy, in kj mol, associated with crimson light of wavelength 67 nm. 2 (4) [X02/70] Page ten

11 Marks 4. cis-platin is a highly successful anti-cancer drug. The formula for cis-platin is [Pt(N 3 ) 2 l 2 ]. (a) cis-platin works by forming a complex with parts of a N molecule. These parts of the N form bonds through nitrogen atoms to Pt(N 3 ) 2 as shown below. 3 N N 3 Pt O N O N Parts of N molecule _ N N _ N N N N 2 N 2 N (i) (ii) Explain why N can be classified as a bidentate ligand in this complex. What feature of the N makes it suitable as a ligand? (b) raw a possible structure for the geometric isomer of cis-platin. (3) 5. The equation for the decomposition of ammonium dichromate is (N 4 ) 2 r 2 O 7 (s) N 2 (g) O( ) + r 2 O 3 (s) onsider the following data for the reaction at 298 K. Substance f /kj mol S /J K mol (N 4 ) 2 r 2 O 7 (s) N 2 (g) 2 O( ) r 2 O 3 (s) (a) (b) For the decomposition of (N 4 ) 2 r 2 O 7, calculate (i) (ii) S (iii) G. hromium burns in excess oxygen to form chromium(iii) oxide. From the information in the table, deduce a value for the enthalpy of combustion of chromium. 2 (5) [Turn over [X02/70] Page eleven

12 6. Sodium hypochlorite, NalO, is the active ingredient in household bleach. The concentration of the hypochlorite ion, lo, can be determined in two stages. In stage, an acidified iodide solution is added to a solution of the bleach and iodine is formed. lo (aq) + 2I (aq) (aq) I 2 (aq) + l (aq) + 2 O( ) In stage 2, the iodine formed is titrated with sodium thiosulphate solution. 2S 2 O 3 2 (aq) + I 2 (aq) 2I (aq) + S 4 O 6 2 (aq) 0. 0cm 3 of a household bleach was diluted to 250 cm 3 in a standard flask cm 3 of this solution was added to excess acidified potassium iodide solution. The solution was then titrated with 0. 0 mol l sodium thiosulphate using an appropriate indicator. The volume of thiosulphate solution required to reach the end point of the titration was 20. 5cm 3. (a) (b) alculate the number of moles of iodine which reacted in the titration. alculate the concentration, in mol l, of the lo in the original household bleach. Marks 2 (3) 7. onsider the orn-aber cycle below which represents the formation of caesium fluoride. 2 s(s) + F 2 (g) s + F (s) s + (g) + e + F(g) 328 kj Step Y s + (g) + F (g) s(g) + F(g) s(g) kJ 2 F 2 (g) 744 kj s(s) + 2 F 2 (g) Step X s + F (s) (a) Use the ata ooklet to find the enthalpy values for Step X and Step Y. (b) (c) Name the enthalpy change that has the value 744 kj in this cycle. Use this orn-aber cycle to calculate the enthalpy of formation of caesium fluoride in kj mol. 2 (4) [X02/70] Page twelve

13 8. In a PP, a student added 50 cm 3 of an aqueous iodine solution to 50 cm 3 of cyclohexane in a separating funnel. fter shaking thoroughly, the funnel was left until the following equilibrium was established. Marks I 2 (aqueous) I 2 (cyclohexane) Two layers were formed, each containing dissolved iodine. 0. 0cm 3 of each layer was titrated with sodium thiosulphate solution until the end point was reached. The cyclohexane layer required 8. 8cm 3 of mol l sodium thiosulphate. The aqueous layer required 0. 5cm 3 of mol l sodium thiosulphate. (a) (b) (c) (d) Which indicator is used to show that the end point has been reached? alculate the concentration of iodine in (i) (ii) the cyclohexane layer the aqueous layer. alculate the partition coefficient for iodine between the two solvents. If 00cm 3 of cyclohexane had been used instead of the 50 cm 3, what effect would this have on (i) (ii) the concentration of iodine in the aqueous layer the value of the partition coefficient? (6) [Turn over [X02/70] Page thirteen

14 9. ydrofluoric acid, F, is a weak acid. Marks F(aq) + 2 O( ) 3 O + (aq) + F (aq) student neutralised 25 cm 3 of hydrofluoric acid solution with sodium hydroxide solution and followed the reaction by measuring the p. The graph obtained for this reaction is shown below p 6 4 X Y Volume of sodium hydroxide solution/cm 3 (a) Write the expression for the dissociation constant, K a, of hydrofluoric acid. (b) When exactly half the acid has been neutralised, pk a = p. Using only information from the graph, deduce pk a and thus calculate K a hydrofluoric acid. for 2 (c) The region XY on the graph is sometimes referred to as the buffer region. part from F, what else is present in the solution which enables it to act as a buffer? (d) Indicator Methyl orange lizarin red resol red lizarin yellow pk In Which of the above indicators could be used to detect the end point of this neutralisation reaction? (5) [X02/70] Page fourteen

15 0. mixture of butan--ol and butan-2-ol can be synthesised from -bromobutane in a two stage process. Marks r KO/ 2 5 O 2 O/ + butan--ol 3 2 = 2 + Stage Stage 2 butan-2-ol (a) What type of reaction is taking place in Stage? (b) The bonding in but--ene can be described in terms of sp 2 and sp 3 hybridisation and sigma and pi bonds. (i) (ii) What is meant by sp 2 hybridisation? What is the difference in the way atomic orbitals overlap to form sigma and pi bonds? (c) raw a structural formula for the major product of Stage 2. (d) -romobutane reacts with hydroxide ions in a nucleophilic substitution reaction to produce butan--ol. The following results were obtained for this reaction. Experiment [-romobutane]/mol l [O ]/mol l Initial rate/mol l s (i) (ii) (iii) What is the overall order of this reaction? alculate a value for the rate constant of this reaction, giving the appropriate units. Outline the mechanism for this nucleophilic substitution reaction using structural formulae. 2 2 (9). student devised the following reaction sequence starting from propan--ol, 3 7 O. 3 7 O 3 7 O 2 5 l Y 2 3 Pl O 2 5 OO 2 5 Ol Z 4 5 (a) Name a suitable reagent to carry out (i) Step (ii) Step 3. (b) Name Y. (c) raw a structural formula for Z. 2 (4) [X02/70] Page fifteen [Turn over

16 Marks 2. In a PP, propanone reacts with 2,4-dinitrophenylhydrazine to make the 2,4-dinitrophenylhydrazone derivative as shown below. 3 3 O 2 N N NO 2 N N NO O 3 3 NO 2 NO 2 propanone 2,4-dinitrophenylhydrazine 2,4-dinitrophenylhydrazone derivative (a) (b) (c) What type of reaction is this? The 2,4-dinitrophenylhydrazone derivative formed in the reaction is impure. (i) (ii) ow would the derivative be purified? ow can the technique of derivative formation be used to identify an unknown ketone? Propanone has an isomer. The shortened structural formula of this isomer is 3 2 O. (i) (ii) Which chemical reagent could be used to distinguish between propanone and this isomer and what would be the result? Nuclear magnetic resonance spectroscopy can also be used to distinguish between these two isomers. The proton nmr spectrum for 3 2 O is shown. Relative intensity TMS hemical shift/ppm Sketch the proton nmr spectrum you would obtain for propanone. [X02/70] Page sixteen

17 Marks 2. (c) (continued) (iii) simplified mass spectrum for propanone is shown below. Relative abundance m/z Identify the ion fragments responsible for peaks and. (6) [Turn over for Question 3 on Page eighteen [X02/70] Page seventeen

18 Marks 3. student devised the following reaction scheme starting with benzene. r l NO NO 2 3 SO 3 (a) What type of reaction does benzene undergo in reactions 4? (b) Name a suitable reagent and catalyst for reaction. (c) Reaction 2 involves nitration of benzene. Which reagents are used to produce the NO + 2 ion? (d) What is the molecular formula for the product of reaction 3? (e) The product of reaction 4 was reacted with bromine in the presence of light. raw a structural formula for an organic product of this reaction. (5) [EN OF QUESTION PPER] [X02/70] Page eighteen

19 [LNK PGE]

20 [LNK PGE]

21 2008 hemistry dvanced igher Finalised Marking Instructions Scottish Qualifications uthority 2008 The information in this publication may be reproduced to support SQ qualifications only on a non-commercial basis. If it is to be used for any other purposes written permission must be obtained from the ssessment Materials Team, alkeith. Where the publication includes materials from sources other than SQ (secondary copyright), this material should only be reproduced for the purposes of examination or assessment. If it needs to be reproduced for any other purpose it is the centre s responsibility to obtain the necessary copyright clearance. SQ s ssessment Materials Team at alkeith may be able to direct you to the secondary sources. These Marking Instructions have been prepared by Examination Teams for use by SQ ppointed Markers when marking External ourse ssessments. This publication must not be reproduced for commercial or trade purposes.

22 dvanced igher hemistry General information for markers The general comments given below should be considered during all marking. Marks should not be deducted for incorrect spelling or loose language as long as the meaning of the word(s) is conveyed. Example: nswers like distilling (for distillation ) and it gets hotter (for the temperature rises ) should be accepted. 2 right answer followed by a wrong answer should be treated as a cancelling error and no marks should be given. Example: What is the colour of universal indicator in acid solution? The answer red, blue gains no marks. 3 If a right answer is followed by additional information which does not conflict, the additional information should be ignored, whether correct or not. Example: Why can the tube not be made of copper? If the correct answer is related to a low melting point, and the candidate s answer is It has a low melting point and is coloured grey this would not be treated as a cancelling error. 4 Full marks should be awarded for the correct answer to a calculation on its own whether or not the various steps are shown unless the question is structured or working is specifically asked for. 5 mark should be deducted in a calculation for each arithmetic slip unless stated otherwise in the marking scheme. No marks should be deducted for incorrect or missing units at intermediate stages in a calculation. 6 mark should be deducted for incorrect or missing units unless stated otherwise in the marking scheme. Please note, for example, that KJ mol - is not acceptable for kj mol - and a mark should be deducted. 7 Where a wrong numerical answer (already penalised) is carried forward to another step, no further penalty is incurred provided the result is used correctly. 8 No mark is given for the solution of an equation which is based on a wrong principle. Example: Use the information in the table to calculate the standard entropy change for the reaction: l 2 l 2 l ompound Sº/J K - mol l 87 2 l 2 l 208 Using ΔSº = Sº reactants - Sº products would gain zero marks. Page 2

23 9 No marks are given for the description of the wrong experiment. 0 Full marks should be given for correct information conveyed by a sketch or diagram in place of a written description or explanation. In a structural formula, if one hydrogen atom is missing but the bond is shown, no marks are deducted. Examples: O O Would not be penalised as the structural formula for ethyl ethanoate. If the bond is also missing, then zero marks should be awarded. Example: O O 2 If a structural formula is asked for, 3 and 3 2 are acceptable as methyl and ethyl groups respectively. 3 With structures involving an O or an N 2 group, no mark should be awarded if the O or N are not bonded to a carbon, ie O 2 and N When drawing structural formulae, no mark should be awarded if the bond points to the wrong atom, eg O 5 symbol or correct formula should be accepted in place of a name unless stated otherwise in the marking scheme. 6 When formulae of ionic compounds are given as answers it will only be necessary to show ion charges if these have been specifically asked for. owever, if ion charges are shown, they must be correct. If incorrect charges are shown, no marks should be awarded. 7 If an answer comes directly from the text of the question, no marks should be given. Example: student found that 0 05 mol of propane, 3 8 burned to give 82 4 kj of energy. 3 8 (g) + 5O 2 (g) 3O 2 (g) O(l) Name the kind of enthalpy change which the student measured. No marks should be given for burning since the word burned appears in the text. Page 3

24 8 guiding principle in marking is to give credit for (partially) correct chemistry rather than to look for reasons not to give marks. Example : The structure of a hydrocarbon found in petrol is shown below Name the hydrocarbon. lthough not completely correct, the answer, 3, methyl-hexane would gain the full mark ie wrong use of commas and dashes. Example 2: student measured the p of four carboxylic acids to find out how their strength is related to the number of chlorine atoms in the molecule. The results are shown. Structural formula p 3 OO 65 2 loo 27 l 2 OO 0 90 l 3 OO 0 5 ow is the strength of the acids related to the number of chlorine atoms in the molecule? gain, although not completely correct, an answer like the more l 2, the stronger the acid should gain the full mark. Example 3: Why does the (catalytic) converter have a honeycomb structure? response like to make it work may be correct but it is not a chemical answer and the mark should not be given. Page 4

25 2008 hemistry dvanced igher Marking scheme Section Page 5

26 Marking Instructions hemistry dvanced igher Section Question cceptable nswer Mark Unacceptable nswer (a) Octahedral/square bipyramidal 5 bonded pairs and lone pair (b) NF3 has 4 electron pairs, F3 has 3 electron pairs NF3 tetrahedral arrangement of electron pairs, F3 trigonal planar arrangement of electron pairs NF3 has lone pair Lone pair on N NF3 has extra pairs ut not cancelling NF3 has an extra electron pair, N has an extra pair Page 6

27 Question cceptable nswer Mark Unacceptable nswer 2 (a) Green (b) (i) +3 or 3+ or 3 or III or Three -3 (ii) Tetraamminedichlorocobalt(III) Tetraaminedichlorocobalt(III) (follow through from (b)(i)) Tetraamminedichlorocobaltate(III) ichlorotetraamminecobalt (III) ate ccept a instead of aa amine instead of ammine (iii) s 2 2s 2 2p 6 3s 2 3p 6 3d 6 (again, follow through from (b)(i)) [r] 3d 6 Page 7

28 Question cceptable nswer Mark Unacceptable nswer 3 (a) (Excited) electrons emitting energy as they fall (back) down to lower energy levels d d transitions (b) Wavelength of emitted light is outwith the visible part of the spectrum or Temperature too low Emission in U.V. or I.R. Flame not hot enough No d electrons Mg has full 2s shell (c) E Lhc λ = = = 0 marks = (kj mol - ) (or 78) = mark only or = mark only Page 8

29 Question cceptable nswer Mark Unacceptable nswer 4 (a) (i) It coordinates through 2 sites to the platinum as 2 lone pairs Forms 2 bonds to the Pt Pt is attached to 2 parts of the N Forms 2 dative bonds to the Pt (ii) Lone pairs of electrons Non bonded pairs Unbonded pairs Free electron pairs Electron pairs Free electrons Unpaired electrons (b) l N3 Pt 3N l Tetrahedral diagram l N3 Pt N3 l Page 9

30 Question cceptable nswer Mark Unacceptable nswer 5 (a) (i) Δ o = Σ o products Σ o reactants = (4-286) -40 (-806) = -478 kj mol - (ii) ΔS o = ΣS o products ΣS o reactants = 92 + (4 70) = 27 J K - mol - (iii) ΔG o = Δ o TΔS o = -478 (298 27)/000 = kj mol - or -543 kj mol - (Follow through from incorrect answers) (See below for combinations of follow through possibilities) Δ o kj mol - ΔS o J K - mol - ΔG o kj mol orrect * ΔS wrong +380 * +7 * Δ/ΔS wrong +380 * Δ wrong * omitted 4 2O (b) -570 kj mol - Penalise once only in question 5 for wrong or missing units Page 0

31 Question cceptable nswer Mark Unacceptable nswer 6 (a) Number of moles of S2O3 2- = = or Number of moles of iodine which reacted = or (b) Moles of lo - in 25 cm 3 of bleach solution = So moles of lo - in 250 cm 3 of bleach solution = Original concentration in 0.0 cm 3 of bleach = n/v = =.025 (mol l - ) ccept correct follow through from (a) Page

32 Question cceptable nswer Mark Unacceptable nswer 7 (a) Step X = 77 kj or 77 kj mol - Step Y = 382 kj or 382 kj mol - Lose maximum of mark if no units given in one or both answers (b) Lattice enthalpy Lattice Lattice formation (c) Δformation = = (kj mol - ) orrect follow through from (a) [ X + Y calculated correctly = mark] Page 2

33 Question cceptable nswer Mark Unacceptable nswer 8 (a) Starch solution Starch iotec (b) (i) moles of thiosulphate = = or So moles of I2 = or [I2]cyclohexane = /0.0 = mol l - (or mol l - ) (ii) Moles thiosulphate = = or So moles of I2 = [I2]aqueous = / 0.0 = mol l - or mol l - or = mol l - or mol l Page 3

34 Question cceptable nswer Mark Unacceptable nswer (c) K = [I2]cyclohexane = [I2]aqueous ny units given nswer to b(ii) nswer to b(i) = (or if used) 0.9 b(i) b(ii) correct follow through (d) (i) It decreases hanged/increased ny indication that value goes down (ii) It would stay the same Little change No change No effect Page 4

35

36 Question cceptable nswer Mark Unacceptable nswer 0 (a) Elimination Nucleophilic elimination (b) (i) sp 2 hybridisation is a mixing of one s orbital and two p orbitals, (hybridising of one s orbital and two p orbitals) s orbital (ii) Sigma bonds end on overlap of (atomic) orbitals Pi bonds sideways overlap of (atomic) orbitals 2 correct diagrams Overlap between 2 carbons (c) or 32O3 O Page 6

37 Question cceptable nswer Mark Unacceptable nswer (d) (i) 2 nd order (ii) Rate = k[o - ][-bromobutane] k = = or Units = l mol - s - orrect units = mark ccept correct follow through from (d) (i) (see below for follow through) [ bromobutane] [O - ] k mol - s - (0.25) mol -2 s (0.0) mol -2 s - (0.25) 2 (0.0) mol -3 s - (iii) r 4 9 O O - O r r 37 O ve charge must be given outside the brackets or on the (in the transition state) Page 7

38 Question cceptable nswer Mark Unacceptable nswer (a) (i) Sodium metal or any reactive metal ny Gp metal and a Mg NaO a (ii) (ot) copper (II) oxide or acidified dichromate or acidified permanganate or correct formulae + /MnO4 - + /r2o7 2- Tollens enedict s/fehlings + /MnO4 + /r2o7 reagents opper oxide cidified chromate (b) Ethoxypropane or ethylpropylether Propoxyethane Propylethylether o not accept formulae (c) O 32 O OO23 25 OO25 Page 8

39 Question cceptable nswer Mark Unacceptable nswer 2 (a) ondensation or addition + elimination (b) (i) y recrystallisation/crystallisation Evaporate off the water (ii) Measure melting point of derivative and compare with literature values/expected value/data book value/known value oiling point instead of MP Measure melting point (c) (i) Fehling s solution and blue to orange/brown with the isomer (propanal) or enedict s orange/red/green Tollens reagent and silver mirror with the isomer cidified dichromate and orange to green with the isomer cidified permanganate and purple to colourless with the isomer (ot) copper (II) oxide and black to brown with the isomer 3 points ldehyde/reagent/result (final) or Ketone/reagent/result ancelling errors eg propanone instead of propanal (ii) Peak must lie between 2.0 and 3.0 Line on (iii) = 3 + harges not needed = 3O + or 23O + Negative charges Labels and wrong way round Page 9

40 Question cceptable nswer Mark Unacceptable nswer 3 (a) Electrophilic substitution Nucleophilic substitution (b) r2 and Fer3/Fel3/lr3/Fe/ll3 orrect answers in words rather than formulae (c) Sulphuric acid and nitric acid 2SO4 and NO3 oncentrated/fuming 2SO4 + NO3 ilute 2SO4 and NO3 (d) 66SO3 ny order 65SO3 (e) 2r or r2 or r3 [EN OF MRKING INSTRUTIONS] Page 20