TIME 1 hour 15 minutes. INSTRUCTIONS TO CANDIDATES Write your Centre Number and Candidate Number in the spaces provided at the top of this page. Answer all sixteen questions. Answer all ten questions in Section A. Record your answers by marking the appropriate letter on the answer sheet provided. Use only the spaces numbered 1 to 10. Keep in sequence when answering. Answer all six questions in Section B. Write your answers in the spaces provided in this question paper. INFORMATION FOR CANDIDATES The total mark for this paper is 90. Quality of written communication will be assessed in question 14(c). In Section A all questions carry equal marks, i.e. two-marks for each question. In Section B the figures in brackets printed down the right-hand side of pages indicate the marks awarded to each question or part question. A Periodic Table of Elements (including some data) is provided. ADVANCED General Certificate of Education 2006 Chemistry Assessment Unit A2 2 assessing Module 5: Analytical, Transition Metals and Further Organic Chemistry [A2C21] FRIDAY 2 JUNE, MORNING A2.2: 2006 - 201 2006-09: Old Old Spec June 2010-1 : Old Spec 245 pages in total here. 6 6 www.franklychemistry.co.uk
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Chemistry · 2 Which one of the following amino acids is optically active and produces a neutral solution when dissolved in water? A NH 2 CH 2 COOH B NH 2 CHCOOH | CH 3 ... 13 Proteins
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TIME
1 hour 15 minutes.
INSTRUCTIONS TO CANDIDATES
Write your Centre Number and Candidate Number in the spaces provided at the top of this page.Answer all sixteen questions.Answer all ten questions in Section A. Record your answers by marking the appropriate letter on the answer sheet provided. Use only the spaces numbered 1 to 10. Keep in sequence when answering.Answer all six questions in Section B. Write your answers in thespaces provided in this question paper.
INFORMATION FOR CANDIDATES
The total mark for this paper is 90.Quality of written communication will be assessed in question 14(c).In Section A all questions carry equal marks, i.e. two-marks for each question.In Section B the figures in brackets printed down the right-hand side of pages indicate the marks awarded to each question or part question.A Periodic Table of Elements (including some data) is provided.
ADVANCEDGeneral Certificate of Education
2006
Chemistry
Assessment Unit A2 2assessing
Module 5: Analytical, Transition Metals and Further
Organic Chemistry
[A2C21]
FRIDAY 2 JUNE, MORNING
A2.2: 2006 - 2012006-09: Old Old SpecJune 2010-1 : Old Spec
For each of the questions only one of the lettered responses (A – D) is correct.
Select the correct response in each case and mark its code letter by connecting the dots as illustrated on the answer sheet.
1 Which one of the following is the electronic structure for the titantium ion, Ti2+, in the ground state?
A 1s22s22p63s23p64s2
B 1s22s22p63s23p63d2
C 1s22s22p63s23p63d14s1
D 1s22s22p63s23p43d24s2
2 Which one of the following amino acids is optically active and produces a neutral solution when dissolved in water?
A NH2CH2COOH B NH2CHCOOH | CH3
C NH2CHCOOH | (CH2)4 | NH2
D NH2CHCOOH | CH2 | COOH
3 Which one of the following statements about benzene is incorrect?
A A total of six electrons per molecule are delocalised. B All of the carbon-carbon bonds are the same length. C The bond angles are all 120°. D The empirical formula is C6H6.
4 Which one of the following analytical techniques depends upon electronic transitions between energy levels?
A infra-red spectroscopy B mass spectrometry C n.m.r. spectroscopy D visible spectroscopy
5 1.06 g of hydrated sodium carbonate, Na2CO3.10H2O, were neutralised by 12.5 cm3 of dilute hydrochloric acid. What is the concentration of the acid in g dm–3?
A 10.8 (1:1) B 21.6 (correct) C 29.2 (anhydrous, 1:1) D 58.4 (anhydrous, 1:2)
6 Which one of the following graphs represents the absorbance against volume in a colorimetry experiment for the solutions of copper(II) sulphate and ammonia given?
7 In which one of the following complex ions is the metal ion in the oxidation state +2?
A [Cr(H2O)5OH]2+
B [CuCl4]2–
C [Fe(SCN)(H2O)5]2+
D [TiCl6]2–
8 The order of increasing basic strength for ammonia, phenylamine and propylamine is
A ammonia, phenylamine, propylamine B phenylamine, propylamine, ammonia C phenylamine, ammonia, propylamine D propylamine, ammonia, phenylamine
9 Methylamine reacts with excess ethanoyl chloride according to the equation:
CH3COCl + CH3NH2 → CH3NHCOCH3 + HCl
6.00 g of N-methyl ethanamide were produced from 4.24 g of methylamine. What is the percentage yield?
A 60.0% (correct) B 66.0% (use ethanoyl chloride etc) C 70.6% (use mass) D 78.6%
10 26.65 g of [Cr(H2O)5]3+.2Cl–.H2O were dissolved in water. The solution was treated with excess silver nitrate solution. What mass of silver chloride precipitate was formed?
A 7.17 g (2:1 ratio) B 14.35 g (only 1 Cl) C 28.70 g (correct) D 43.05 g (3 Cl)
(b) A mixture of ammonia and oxygen is both kinetically and thermodynamically stable. The reaction between ammonia and oxygen is catalysed by platinum.
(i) State the effect of platinum on the thermodynamic and kinetic stability of this mixture.
13 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.
H | NH2 — C — COOH | CH2SeH
(a) (i) Explain why selenocysteine, like other amino acids, has a high melting point.
(iii) Other functional groups may be incorporated onto the benzene ring. Suggest one reason why altering the attached functional group may be useful in the dyestuffs industry.
(ii) In an experiment the yield of phenylhydrazine was 45.36 g. Calculate the volume of 2 M sodium sulphite solution required to produce this amount assuming an 80% yield.
(b) Titrate against standard [1] edta4– [1] indicator – murexide [1] (buffered to) pH of 8/ammonia + ammonium chloride [1] colour change from green/yellow [1] to purple/mauve/blue/violet [1] Maximum of [5] [5]
Quality of written communication [2] 8
15 (a) A = NaCN/KCN [1] B = LiAlH4/Na and C2H5OH [1] C = HNO2/NaNO2 and HCl [1] [3]
(b) Extra peak due to OH [1] at high chemical shift [1] two (superimposed) spectra [1] 2 quartets [1] 2 triplets [1] to maximum of [2] [2]
2NH2 — C — COOH + Na2CO3 → 2NH2 — C — COONa + H2O + CO2
(e) 12 g propan-l-ol = 0.2 mole reacts with 0.2 × 4.5 mole oxygen = 0.9 mole volume of oxygen = 0.9 × 24 = 21.6 dm3
volume of oxygen in 120 dm3 of air = 0.2 × 120 = 24 dm3
excess oxygen = 24 – 21.6 = 2.4 dm3
volume of nitrogen etc. left = 120 –24 = 96 dm3 [1] volume of carbon dioxide formed = 0.2 × 3 = 0.6 mole = 14.4 dm3 [1] total volume of gas = 2.4 + 96 + 14.4 = 112.8 dm3 [1] award [4] directly for correct answer each error [–1] [4] 13
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.
(d) Potassium thiocyanate is prepared by boiling potassium cyanide
solution with sulphur. It is extremely soluble in water and reacts readily
with silver nitrate solution to form a precipitate of silver thiocyanate.
This reaction may be used, as follows, to determine the chloride content
in cheese.
Weigh out accurately approximately 1.5 g of cheese into a conical flask. Add 10 cm3 of water, 25.0 cm3 of 0.05 M silver nitrate solution (an excess) and 10 cm3 of concentrated nitric acid. Boil for 10 minutes. Cool and add a further 50 cm3 of water. The excess silver nitrate is determined by titration with standard potassium thiocyanate solution using an iron(III) indicator. At the end-point the aqueous iron(III) ions react with excess thiocyanate ions.
2 marks The candidate expresses ideas clearly and fl uently through well-linked sentences and paragraphs. Arguments are generally relevant and well-structured. There are few errors of grammar, punctuation and spelling.
1 mark The candidate expresses ideas clearly, if not always fl uently. Arguments may sometimes stray from the point. There may be some errors of grammar, punctuation and spelling, but not such as to suggest a weakness in these areas.
0 marks The candidate expresses ideas satisfactorily, but without precision. Arguments may be of doubtful relevance or obscurely presented. Errors in grammar, punctuation and spelling are suffi ciently intrusive to disrupt the understanding of the passage.
(iii) A = lithium aluminium hydride/lithium tetrahydridoaluminate [1] B = hydrochloric acid [1] C = sodium hydroxide (solution) [1] [3]
(d) (i) known concentration [1]
(ii) (blood) red [1]
(iii) [Fe(SCN)(H2O)5]2+ [1]
(iv) AgNO3 + KSCN → AgSCN + KNO3 [1]
(v) moles of excess thiocyanate = 14.3 × 0.05/1000 = 0.000715 moles of excess silver nitrate = 0.000715 moles of silver nitrate at start = 25.0 × 0.05/1000 = 0.00125 moles of silver nitrate reacting with chloride = 0.00125 – 0.000715 = 0.000535 mass of chloride in cheese = 0.000535 × 35.5 = 0.019 g mass in 1 g = 0.019/1.48 = 0.01284 g
or
volume of silver nitrate solution required to react with chloride = 25 – 14.3 = 10.7 cm3
moles = 10.7 × 0.05/1000 = 0.000535 mass of chloride in cheese = 0.000535 = 0.000535 × 35.5 = 0.019 g mass in 1 g = 0.019/1.48 = 0.01284 g
Award [4] directly for correct answer Each error [–1], carry error through [4] 23
15 (a) forms hydrogen bonds [1] between NH2 group and water [1] [2]
(b) (i) strongest: dopamine weakest: phenylamine [1] dopamine – electrons pushed towards nitrogen/lone pair more available [1] phenylamine – electrons withdrawn by aromatic ring/less available [1] [3]
(ii)
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[1]
(c) (i) C9H11O4N [1]
(ii) carbon atom joined to 4 different [1] atoms or groups [1] [2] or (two) non superimposable [1] mirror images [1]
12 (a) binding or complexation of a multidentate ligand [1] donates more than one pair of electrons/more than one coordination bond [1] octahedral [1] (any two from three) [2]
(b) titrate known volume of Mg2+ solution [1] Buffer to pH 10 [1] indicator [1] eriochrome black solachrome black Colour change [1] (eriochrome) red to blue (solachrome) red to blue ratio (edta to Mg2+) is 1:1 [1] (any four from five) [4] 6
Mass of iron(III) sulphate = 0.012 × 400 = 4.8 g [3] 11
14 (a) (i) Primary structure is the order of its amino acids [1] secondary structures: alpha-helix or beta-pleated sheet [1] tertiary structure is the (full 3-dimensional) folded structure of the polypeptide chain [1] [3]
(ii) COOH/COO– [1] NH2 [1] [2]
(iii) place mixture at origin of chromatographic paper or plate develop using solvent 1 [1] turn paper of plate through 90˚ and develop using solvent 2 [1] locate spots using (ninhydrin) [1] Comparison of Rf values for leucine [1] [4]
Quality of written communication [2]
(b) (i)
Four different groups attached to a carbon atom [1] [3]
(ii) Transfer of H+ from COOH to NH2 [1]
(iii) Strong attraction between + and – charges [2]
(b) Vanadium pentoxide is used as a solid heterogeneous catalyst in the Contact process, catalysing the conversion of sulphur dioxide to sulphur trioxide.
15 Aromatic chemistry is a branch of organic chemistry which includes those compounds with 6-membered ring structures such as benzene and methylbenzene (toluene), C6H5CH3.
(f) Phenylamine reacts with a mixture of sodium nitrite and hydrochloric acid to form benzene diazonium chloride. The benzene diazonium ion forms a scarlet precipitate of azo-2-naphthol when added to an alkaline solution of 2-naphthol.
(i) Sodium nitrite and hydrochloric acid react to form nitrous acid in situ. Write the equation for this reaction.
(ii) Any soluble iron(III) salt, e.g. sulphate, chloride, nitrate [1]
(b) (i) colourless to pink/purple [1] [2]
(ii) moles of iron per litre = 7.84/56 = 0.14 moles of iron in 25 cm3 = 0.14/40 = 3.5 × 10–3
moles MnO4– = 3.5 × 10–3/5 = 7 × 10–4
volume = 7 × 10–4 × 1000/0.1 = 7 cm3
[–1] for each error, carry error through [3]
(c) (i) use known mass of sample (and dissolve to make 250 cm3 solution) [1] known excess [1] of NaOH [1] titrate (25 cm3) portions of above with (standard) hydrochloric acid [1] [4]
(ii) iron(II) ions [1] would form a precipitate (of iron(II) hydroxide)/react with NaOH [1] [2]
(iii) RFM FeSO4 = 152 RFM FeSO4.(NH4)2SO4.6H2O = 392 moles double salt = 20/392 = 0.051 moles of iron(II) sulphate = 0.051 mass of iron(II) sulphate = 0.051 × 152 = 7.75 g each error [–1], carry error through [3] 17
15 (a) petroleum [1]
(b) CH [1]
(c) single/sigma (covalent) bonds( carbon – carbon and carbon – hydrogen) [1] delocalised electrons (above and below plane of ring [1], form pi-bond/overlapping P orbitals [1] bond order of 1.5 between carbon atoms/C–C bond length all equal [1] Any three from four [3]
(ii) structure = [1] name = [1] 1,2– or 1,3– or 1,4–dinitrobenzene [2]
(iii) tin [1] concentrated hydrochloric acid [1] sodium hydroxide [1]
reflux [1] [3]
(f) (i) NaNO2 + HCl → HNO2 + NaCl [1]
(ii)
each error [–1], e.g. missing charge/double bond, etc. [2]
(iii) too unstable [1]
(iv) coupling [1]
(v) C16H12N2O [1]
(vi) conjugated/delocalised electrons/chromophore [1] absorb visible light/radiation [1] to promote electrons (to higher energy level) [1] mention of emission = [–1] [3] Quality of written communication [2] 25
16 (a) look for N–H or C–N (stretch/bend) peaks [1]– benzene–1,4–diammine [1] or C–O/C=O/O–H stretch/bend peaks [1]– benzene–1,4–dicarboxylic acid [1] or one has N–H/peak and the other a C–O/C=O/O–H peak [1] [2]
(b)
[2]
(c) (i) [1]
(ii) peptide [1]
(iii) (strong) hydrogen bonds [1] between different chains [1] [2] 8
Analytical, Transition Metals, Electrochemistryand Further Organic Chemistry
[AC222]
TUESDAY 1 JUNE, AFTERNOON
TIME
2 hours.
INSTRUCTIONS TO CANDIDATES
Write your Centre Number and Candidate Number in the spaces provided at the top of this page.Answer all seventeen questions.Answer all ten questions in Section A. Record your answers by marking the appropriate letter on the answer sheet provided. Use only the spaces numbered 1 to 10. Keep in sequence when answering.Answer all seven questions in Section B. Write your answers in the spaces provided in this question paper.
INFORMATION FOR CANDIDATES
The total mark for this paper is 120.Quality of written communication will be assessed in question 16(b).In Section A all questions carry equal marks, i.e. two marks for each question.In Section B the figures in brackets printed down the right-hand side of pages indicate the marks awarded to each question or part question.A Periodic Table of Elements (including some data) is provided.
6 The nmr spectrum of a compound X is shown below.
Which one of the following is X?
A CH3CH2CH2COOH B CH3CH2COOCH2CH3 C CH3COOCH2CH3 D CH3CH2COOH
7 A green solid was dissolved in water and the resulting solution divided into two portions. Sodium hydroxide solution was added to one of the portions and ammonia solution to the
other. The results are summarised in the table below.
Solution added Few drops of solution Excess solution
Sodium hydroxide solution Green precipitate No effect
Ammonia solution Green precipitate Dissolves to form a blue solution
Which one of the following ions was present in the green solid?
A Cr3+
B Cu2+
C Fe2+
D Ni2+
8 Which one of the following is the colour of chrome alum crystals?
(c) Explain in terms of entropy why dimethylglyoxime displaces the water ligands in the hydrated nickel(II) ion to form the nickel(II) dimethylglyoxime complex.
13 (a) Polydentate ligand: a ligand with more than one lone pair of electrons which forms more than one central bond (with a coordinate/dative metal) [2]
(b) (i) 4 [1]
(ii) Square planar [1]
(iii) : Covalent bond [1] ----- : Hydrogen bond [1] : Dative/Co-ordinate bond [1] [3]
(c) (dimethylglyoxime) replaces 6 water molecules/ or 3 molecules → 7 molecules. [1] This increases the overall entropy [1] [2] 9
(iii) Conjugated (double bonds)/Delocalised/Energy levels close together [1] Hence electron excited/move to higher energy level [1] Removes a colour from light [1] [3] 25
15 (a) Transition metal atoms/ions have an incomplete d-subshell. [1]
(b) (i) 2SO2 + O2 → 2SO3 [1]
(ii) It is in a different physical state from the reactants. [1]
(iii) Reactants adsorb onto the surface [1] Bonds weakened in the reactants [1] Bonds form in products and products are desorbed from the surface [1] Orientation/closer together/lower activation energy [1] Any 3 from 4 [3]
(iii) Colour change from orange to yellow [1] H+ ions will be removed [1] Equilibrium moves to the left [1] [3] 17
16 (a) (i) C18H27O3N [1]
(ii) 100 cm3 contain 5 g 1000 cm3 contain 50 g
= 0.164 mol dm–3 [3]
(b) Place sample at the corner of a chromatogram [1] Run the chromatogram in a suitable solvent [1] (Dry chromatogram and) run at right angles in a different solvent [1] Development + Compare Rf values or chromatogram run with capsaicin [1] Quality of written communication [2] [6] 10
17 (a) (i) Primary: sequence of amino acids [1] Secondary: alpha helix/beta pleated sheet [1] due to the formation of a hydrogen bond between the nitrogen of one peptide bond and the oxygen of another further along the chain [1] Tertiary: cross links between amino acids [1] due to H-bonds between amino acids/electrostatic attractions between polar groups/ dipole–dipole interactions/Van der Waals forces between non-polar groups/disulphide bridges [1] [5]
(ii) The enzyme provides an active site [1]/lock and key mechanism [1] [2]
(iii) High temperature denatures the enzyme [1] the structure and the active site is no longer functional [1] (disrupts the secondary and tertiary structures by breaking bonds [1]) Any two [2]
Analytical, Transition Metals, Electrochemistry and Further Organic Chemistry
[AC222]
FRIDAY 27 MAY, AFTERNOON
TIME
2 hours.
INSTRUCTIONS TO CANDIDATES
Write your Centre Number and Candidate Number in the spaces provided at the top of this page.Answer all fifteen questions.Answer all ten questions in Section A. Record your answers by marking the appropriate letter on the answer sheet provided. Use only the spaces numbered 1 to 10. Keep in sequence when answering.Answer all five questions in Section B. Write your answers in the spaces provided in this question paper.
INFORMATION FOR CANDIDATES
The total mark for this paper is 120.Quality of written communication will be assessed in question 13(d)(iii).
In Section A all questions carry equal marks, i.e. two marks for each question.In Section B the figures printed down the right-hand side of pages indicate the marks awarded to each question or part question.A Periodic Table of Elements (including some data) is provided.
For each of the questions only one of the lettered responses (A–d) is correct.
Select the correct response in each case and mark its code letter by connecting the dots as illustrated on the answer sheet.
1 Chlorine has two isotopes, chlorine-35 and chlorine-37. Which one of the following is the number of peaks found in the mass
spectrum of chlorine gas?
A 2 B 3 C 4 d 5
2 The mechanism for the nitration of benzene is described as
A electrophilic addition. B electrophilic substitution. C nucleophilic addition. d nucleophilic substitution.
3 Copper(II) ions form a coloured complex with the ligand L. The following absorbances were recorded on mixing different volumes of 0.05 M copper(II) sulfate and 0.1 M ligand L.
volume of 0.05 M CuSO4(aq)/cm3
volume of 0.1 M L(aq)/cm3 absorbance
3.0 7.0 0.412
4.0 6.0 0.457
5.0 5.0 0.406
6.0 4.0 0.335
7.0 3.0 0.251
Which one of the following is the cation to ligand ratio in this complex?
4 In which one of the following is a metal in the +2 state?
A [Ag(nH3)2]
B [Co(nH3)5Br]2
C K4Fe(Cn)6 d K2Cr2O7
5 An organic compound X contains carbon, hydrogen and oxygen only. When 1.29 g of X is burnt completely, 3.30 g of carbon dioxide and 1.35 g of water are formed. Which one of the following is the empirical formula of X?
A CH2O B C2H6O C C4H8O d C5H10O
6 Which one of the following is the relative molecular mass of 2,4-dichloro-3,5-dimethylphenol?
A 190 B 191 C 192 d 196
7 Given the following standard electrode potentials:
E
φ
/V V3(aq) e V2(aq) 0.26 SO4
2(aq) 2H(aq) 2e SO32(aq) H2O(l) 0.17
VO2(aq) 2H(aq) e V3(aq) H2O(l) 0.34 Fe3(aq) e Fe2(aq) 0.77 VO2
(aq) 2H(aq) e VO2(aq) H2O(l) 1.00
Which one of the following reagents will convert V3+(aq) to VO2+(aq)?
A Aqueous iron(II) ions B Aqueous iron(III) ions C Aqueous sulfate ions in acidic solution d Aqueous sulfite ions
8 Which one of the following is the volume of water which must be added to 30.0 cm3 of 0.25 mol dm3 sulfuric acid to produce 0.05 mol dm3 sulfuric acid?
A 30 cm3
B 120 cm3
C 150 cm3
d 270 cm3
9 Which one of the following is the total number of electrons involved in bonding in benzene?
A 12 B 18 C 24 d 30
10 The concentration of aqueous magnesium ions may be determined by titration with standard edta using Eriochrome Black T as indicator. Which one of the following is the colour change at the end point?
A Blue to green B Blue to red C Red to blue d Red to green
12 Chromium is a transition metal which was discovered by Louis Vauquelin in 1797. He was able to detect traces of chromium in precious gems, such as ruby and emerald.
(a) State the electronic structure of a chromium atom and explain why the arrangement is stable.
(c) Chromium trioxide, CrO3, is formed by the reaction between excess concentrated sulfuric acid and a concentrated solution of potassium dichromate. Potassium sulfate and water are formed as by-products.
13 The first person to extract ethanoic acid from vinegar was the alchemist Jabir ibn Hayyan Geber (c. 721–815 AD). However the pure compound was not produced for another ten centuries.
(a) The mass spectrum of ethanoic acid shows a distinct peak at m/e 59. State the formula of the species giving rise to this peak.
(b) Ethanoic acid reacts with ethanol to form the ester ethyl ethanoate, CH3COOC2H5. The n.m.r. spectrum of ethyl ethanoate consists of three sets of peaks as shown below.
(iii) Ethanamide is hydrolysed by either hydrochloric acid or sodium hydroxide to form different organic products. State the formula of the organic product in each case.
(i) describe, with observations, how you could confirm the presence of aqueous iron(III) ions, following the oxidation of iron(II) ions, without interference from manganese(II) ions.
(ii) 25.0 cm3 of an acidified iron(II) ethanedioate solution required 32.2 cm3 of 0.025 mol dm3 of potassium manganate(VII) solution for complete reaction. Calculate the concentration, in mol dm3, of the iron(II) ethanedioate solution.
(iii) determine melting point/description of apparatus heat slowly record temperature when melting starts and stops/range compare to tables Any four [4]
Quality of written communication [2] (e) (i) two coordinate (dative) bonds
formed by lone pairs [2]
(ii) [Ni(H2O)6]21 1 3en [Ni(en)3]21 1 6H2O [2] unbalanced [1]
(iii) increase in entropy [1] 4 particles to 7 particles [1] [2] 26
Analytical, Transition Metals, Electrochemistry and Further Organic Chemistry
[AC222]
WEDNESDAY 23 MAY, AFTERNOON
TIME
2 hours.
INSTRUCTIONS TO CANDIDATES
Write your Centre Number and Candidate Number in the spaces provided at the top of this page.Answer all seventeen questions.Answer all ten questions in Section A. Record your answers by marking the appropriate letter on the answer sheet provided. Use only the spaces numbered 1 to 10. Keep in sequence when answering.Answer all seven questions in Section B. Write your answers in the spaces provided in this question paper.
INFORMATION FOR CANDIDATES
The total mark for this paper is 120.Quality of written communication will be assessed in question 16(c)(i).
In Section A all questions carry equal marks, i.e. two marks for each question.In Section B the figures printed down the right-hand side of pages indicate the marks awarded to each question or part question.A Periodic Table of Elements (including some data) is provided.
For each of the following questions only one of the lettered responses (A-D) is correct.
Select the correct response in each case and mark its code letter by connecting the dots as illustrated on the answer sheet.
1 Which one of the following applies to the ligand substitution reaction shown?
[Ni(H2O)6]21 1 3en [Ni(en)3]21 1 6H2O
Change in Coordination Number �S º
A 6 to 3 negative B 6 to 3 positive C none negative D none positive
2 Which one of the following lists the compounds in order of increasing base strength?
A ethanamide, methylamine, phenylamine B ethanamide, phenylamine, methylamine C methylamine, ethanamide, phenylamine D phenylamine, ethanamide, methylamine
3 The reaction of 4-hydroxyphenylamine to produce paracetamol is shown below.
CH3COCI � � HCI
NH2
OH
N CH3C
O
OH
H
If the reaction has an 80% yield, 10.9 g of 4-hydroxyphenylamine produces
A 12.1 g of paracetamol. B 13.6 g of paracetamol. C 15.1 g of paracetamol. D 18.9 g of paracetamol.
4 Which one of the following methods may be used to separate a mixture of amino acids obtained from protein hydrolysis?
A distillation B recrystallisation C solvent extraction D thin-layer chromatography
5 Which one of the following is a correct statement about the stereochemistry of the complex [Pt(NH3)2Cl2]?
A It is square planar and has cis/trans isomers. B It is square planar and has two optical isomers. C It is tetrahedral and has cis/trans isomers. D It is tetrahedral and has two optical isomers.
6 25.0 cm3 of potassium iodate(V) solution were added to excess potassium iodide solution dissolved in sulfuric acid. The iodine liberated required 30.0 cm3 of 0.05 mol dm3 Na2S2O3 solution. Which one of the following is the concentration of the potassium iodate(V) solution?
A 0.01 mol dm3
B 0.02 mol dm3
C 0.04 mol dm3
D 0.05 mol dm3
7 Which one of the following gives the ground state electronic configuration for the copper atom and the copper(II) ion?
8 The diagram below shows the titration of a solution of magnesium ions with edta using Eriochrome Black T as indicator.
edta solution
magnesium ions� indicator
What is the colour change at the end point?
A blue to red B green to blue C red to green D red to blue
9 Which one of the following statements about glycine is not correct?
A It has a relatively high melting point. B It contains 32% carbon by mass. C It exists as optical isomers. D It is soluble in water.
10 Which one of the following statements about propanamide is not correct?
A It produces an M11 peak at 73 in its mass spectrum. B It can be dehydrated to form propanenitrile. C It has the molecular formula C3H7NO. D It is a weaker base than ammonia.
(b) Amino acids, such as lysine and valine, also contain the amino group.
H2N — C — COOH
H
CH2(CH2)2NH2
Iysine
H2N — C — COOH
H
CH(CH3)2
valine
(i) Draw the zwitterion of valine.
[1]
(ii) Draw the structure of lysine when it is dissolved in an excess of a strong acid.
[2]
(iii) Draw the structures of the two dipeptides which can be formed from one molecule of glycine and one molecule of alanine. Circle the peptide link in each structure.
13 Nuclear magnetic resonance spectroscopy (nmr) is an important analytical technique.
(a) In the question below, draw one possible structure for each of the compounds A, B, C and D.
(i) Compounds A and B are isomers with the molecular formula C4H8O2. Both have a triplet, a singlet and a quartet in their nmr spectrum.
A B
[2]
(ii) Compound C has the molecular formula C6H12 and has only one peak in its nmr spectrum.
[1]
(iii) Compound D has the molecular formula C5H13N. It is a tertiary amine with three types of chemically equivalent hydrogen atom which exist in the ratio of 6:6:1 and produce a doublet in the nmr spectrum.
14 Iron(II) ions are part of the structure of haemoglobin. Many people supplement their diet by taking “iron tablets” which contain hydrated iron(II) sulfate, FeSO4.7H2O.
(a) “Iron tablets” with a total mass of 8.00 g were dissolved in dilute sulfuric acid and the solution was made up to 250 cm3 in a volumetric flask. 25.0 cm3 portions of this solution were titrated with 0.02 mol dm3 acidified potassium manganate(VII). The average titre was found to be 24.0 cm3.
(i) Write the equation for the reaction of acidified manganate(VII) ions with iron(II) ions.
[2]
(ii) What is the colour change at the end point of this titration?
[2]
(iii) Calculate the percentage of hydrated iron(II) sulfate in the tablets.
(b) The [Fe(H2O)6]31 ion behaves as a Brønsted acid by the loss of one hydrogen ion.
(i) Write an equation to show [Fe(H2O)6]31 behaving as a Brønsted acid.
[2]
(ii) Write the expression for the acid dissociation constant of the [Fe(H2O)6]31 ion.
[1]
(iii) What is observed when sodium hydroxide solution is added to a solution containing [Fe(H2O)6]31 ions?
[2]
(iv) Describe a different chemical test, including observations, which can be used to detect the presence of low concentrations of [Fe(H2O)6]31 ions. Give the formula of any new complex formed.
[4]
(c) With reference to the iron(II) ions in haemoglobin, explain why breathing carbon monoxide can result in death.
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 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]
(iii) Draw a flow scheme to show the mechanism of the mononitration of methyl benzoate and name the mechanism.
17 Polymers are long chain molecules produced by addition or condensation reactions. Polyesters and polyamides are the two main types of condensation polymer.
(a) The polyamide nylon-6,6 is made by a condensation reaction between 1,6-diaminohexane and hexanedioic acid. Draw a section of the polymer showing two repeating units.
[3]
(b) The repeating unit of the polymer PET is shown below:
O
C
O
C O OCH2
CH2
(i) Draw the structure of the smaller of the two monomers.
(iii) moles of manganate(VII) = 0.00048 moles of iron(II) in 25 cm3 = 0.0024 moles of iron(II) in 250 cm3 = 0.024 mass of FeSO4.7H2O = 0.024 × 278 = 6.672 g % hydrated iron(II) sulfate = 83.4% [5] Each error [–1]
16 (a) Does not have an incomplete d-subshell in its (stable) ion [1] Zn2+ is 3d10 [1] [2]
(b) (i) VO2+ + 4H+ + 3e– → V2+ + 2H2O [2]
(ii) 2VO2+ + 8H+ + 3Zn → 2V2+ + 4H2O + 3Zn2+ [2]
(iii) Ion ColourVO2
+ Yellow [1]VO2+ [1] BlueV3+ [1] Green
V2+ Violet [1]
[4]
(c) (i) dissolve in water and add (excess) potassium hydroxide [1] a green-blue precipitate will form and then dissolve to give a deep green solution [1] add excess hydrogen peroxide and heat [1] the (green) solution turns yellow [1] boil the solution (and reduce the volume) [1] add named acid [1] orange solution/orange crystals [1] maximum [6] [6]
Quality of written communication [2]
(ii) moles of chromium(III) chloride hexahydrate = 0.05 [1] theoretical yield of potassium dichromate = 0.025 mole [1] actual yield = 0.00997 mole [1] % yield = 40% [1] [4] 22
Write your Centre Number and Candidate Number in the spaces provided at the top of this page.Answer all fourteen questions.Answer all ten questions in Section A. Record your answers by marking the appropriate letter on the answer sheet provided. Use only the spaces numbered 1 to 10. Keep in sequence when answering.Answer all four questions in Section B. Write your answers in the spaces provided in this question paper.
INFORMATION FOR CANDIDATES
The total mark for this paper is 120.Quality of written communication will be assessed in question 13(e)(iii).
In Section A all questions carry equal marks, i.e. two marks for each question.In Section B the figures printed down the right-hand side of pages indicate the marks awarded to each question or part question.A Periodic Table of the Elements, containing some data, is included in this question paper.
ADVANCEDGeneral Certificate of Education
2013
8214.02R
Chemistry
Assessment Unit A2 2assessing
Analytical, Transition Metals, Electrochemistry and Further Organic Chemistry
[AC222]
TUESDAY 4 JUNE, AFTERNOON
Centre Number
71
Candidate Number
AC
222
For Examiner’suse only
Question Number Marks
Section A
1–10
Section B
11
12
13
14
TotalMarks
1106
05
8214.02R 2
Section A
For each of the following questions only one of the lettered responses (A–D) is correct.
Select the correct response in each case and mark its code letter by connecting the dots as illustrated on the answer sheet.
1 The standard electrode potentials for some half-cells are listed below:
Cu21(aq) 1 2e2 Cu(s) 10.34 V
AgCl(s) 1 e2 Ag(s) 1 Cl2(aq) 10.22 V
H1(aq) 1 e2 1–2 H2(g) 0.00 V
Zn21(aq) 1 2e2 Zn(s) 20.76 V
Which one of the following cell potentials could be obtained by combining two of these standard electrodes?
A 0.42 V
B 0.54 V
C 0.56 V
D 0.98 V
2 In which one of the following reactions is the inorganic reagent acting as an electrophile?
A CH3CH3 1 Cl2 CH3CH2Cl 1 HCl
B CH4 1 4Cl2 CCl4 1 4HCl
C 1 Br2 Br 1 HBr
D CH3 1 Br2 CH2Br 1 HBr
3 Which one of the following is the total number of isomers, both structural and stereoisomers, which are possible for the formula C4H10O?
A 3 or less
B 4
C 5
D 6 or more
8214.02R 3 [Turn over
4 Which one of the following is the name of the indicator used for the titration of magnesium ions with edta?
A Eriochrome
B Eriochrome T
C Eriochrome brown T
D Eriochrome black T
5 The structure of the polymer perspex is shown below.
C C C C C C
H H H
H H H CO2CH3 CO2CH3 CO2CH3
CH3 CH3 CH3
Which one of the following structures is that of the monomer from which perspex is formed?
CH3
CO2CH3
H
H
A
C C
H
CO2CH3
CH3
H
B
C C
CH3
CO2CH3
H
CH3
C
C C
H
CO2CH3
H
H
D
C C
6 Which one of the following statements describes the primary structure of a protein?
A The formation of the a-helix
B The folding of the a-helix
C The sequence of the amino acids in the chain
D The sequence of peptide links in the chain
8214.02R 4
7 Which one of the following graphs represents the absorbance against volume in a colorimetry experiment for the reaction of copper(II) nitrate with ammonia?
0.05 M (Cu(NO3)2(aq)0.10 M NH3(aq)
absorbance
010
55
10 0
volume (cm3)
A
absorbance
010
6.63.3
10 0
volume (cm3)
0.10 M (Cu(NO3)2(aq)0.05 M NH3(aq)
B
0.05 M (Cu(NO3)2(aq)0.10 M NH3(aq)
absorbance
010
3.36.6
100
volume (cm3)
C
0.10 M (Cu(NO3)2(aq)0.05 M NH3(aq)
absorbance
010
55
100
volume (cm3)
D
8214.02R 5 [Turn over
8 Which one of the following compounds is the least soluble in water at room temperature?
A CH3CH(NH2)CO2H
B CH3CH2CH2 NH2
C C6H5CO2Na
D C6H5NH2
9 In which one of the following reactions is the transition metal, transition metal compound or ion not acting as a catalyst?
A Iron in the production of ammonia
B Nickel in the formation of ethane from ethene
C Silver ions in the oxidation of ethanal
D Vanadium pentoxide in the manufacture of sulfuric acid
10 Complete combustion of 0.70 dm3 of a gaseous organic compound at 20 oC and one atmosphere pressure gave 0.12 mole of carbon dioxide.
Which one of the following is the number of carbon atoms in one molecule of the compound?
A 1
B 2
C 4
D 6
8214.02R 6
Examiner Only
Marks Remark
Section B
Answer all four questions in the spaces provided.
11 Benzedrine is the trade name for a mixture of the optical isomers of amphetamine. It was used as a stimulant in World War II and continues to be used in this way today.
(a) Benzedrine may be synthesised by the route shown below.
1 2 3 4 CH2CH2CH3 CH5CHCH3 CH2CHBrCH3 CH2CHNH2CH3
benzedrine
(i) In step 1 a reaction occurs which has a very similar mechanism to that of the monobromination of benzene. With bromination the electrophile is Br1, in this case the electrophile is CH3CH2CH2
1. Draw a flow scheme for this reaction.
[3]
(ii) In step 2 the propylbenzene is broken down into smaller molecules (cracked) in the presence of zinc oxide. Suggest the role of the zinc oxide and the conditions under which the cracking is carried out.
[3]
Examiner Only
Marks Remark
8214.02R 7 [Turn over
(iii) In step 3 name the reagent which adds across the double bond.
[1]
(iv) In step 4 name the reagent which is used to replace the bromine atom in the compound.
[1]
(b) (i) Deduce and explain whether benzedrine is a primary, secondary or tertiary amine.
[2]
(ii) Explain its strength as a base compared with phenylamine.
[2]
(c) Benzedrine forms salts with inorganic acids. The sulfate salt is often used as the main form of benzedrine in medicine.
(i) Write the equation for the formation of the sulfate salt of benzedrine.
[2]
(ii) Suggest why the formation of an ionic salt is more beneficial if tablets of the drug are used.
[1]
(iii) The amine can be liberated from the salt. Name the reagent and the conditions used for this reaction.
[2]
Examiner Only
Marks Remark
8214.02R 8
(d) Benzedrine is optically active and exists in two forms one of which is more biologically active than the other. This variation in activity is explained in a similar way to that of enzyme activity.
(i) Explain why benzedrine is optically active.
[1]
(ii) Explain why one structure is more biologically active than the other.
[1]
(e) The identification of many drugs uses the technique of GLC. Explain how this is carried out.
[2]
Examiner Only
Marks Remark
8214.02R 10
12 Iron is a transition element that forms a wide variety of complexes and salts. For example, with ethanedioic acid (oxalic acid) iron can form salts such as iron(II) oxalate and iron(III) oxalate. It can also form complexes such as potassium iron(III) oxalate.
COOH COOH
oxalic acid
(a) (i) Write the formulae of iron(II) oxalate and iron(III) oxalate.
iron(II) oxalate [1]
iron(III) oxalate [1]
(ii) The oxalate ion is colourless. What are the expected colours of the aqueous oxalate solutions listed below?
aqueous iron(II) oxalate [1]
aqueous iron(III) oxalate [1]
(iii) State and explain what would be observed when a solution of sodium hydroxide is added to each of the solutions.
[4]
(b) Iron(II) oxalate, when heated, decomposes to produce iron(II) oxide and both oxides of carbon. Write the equation for the reaction.
[1]
Examiner Only
Marks Remark
8214.02R 11 [Turn over
(c) Iron(II) oxalate is completely oxidised by acidified potassium manganate(VII). The iron(II) ion is oxidised to iron(III):
Fe21 Fe31 1 e2
The oxalate ion is completely oxidised to carbon dioxide.
COO2
2CO2 1 2e2
COO2
The electrons produced react with the manganate(VII) ion.
MnO42 1 8H1 1 5e2 Mn21 1 4H2O
(i) Write the equation for the reaction of acidified manganate(VII) ions with iron(II) oxalate.
[2]
(ii) Oxalic acid is used to remove iron stains because iron dissolves to form iron(II) oxalate. Calculate the mass of iron, in milligrams, dissolved in a 100 cm3 solution if 20.0 cm3 of the iron(II) oxalate solution reacts with 18.2 cm3 of 0.002 M potassium manganate(VII) solution.
[4]
Examiner Only
Marks Remark
8214.02R 12
(d) The oxalate ion also acts as a bidentate ligand. For example, iron(III) ions form the complex K3Fe(C2O4)3. The structure of the trisoxalato anion is based on an octahedron.
(i) Explain the meaning of the term complex.
[2]
(ii) Explain the meaning of the term bidentate ligand.
[2]
(iii) Suggest a 3D structure for the trisoxalato anion.
[2]
(iv) Explain why the trisoxalato anion is optically active.
[2]
(e) If a solution of K3Fe(C2O4)3 is treated with edta a reaction takes place. Suggest what reaction takes place and explain why it occurs.
[2]
Examiner Only
Marks Remark
8214.02R 14
13 Propanamide is a white crystalline solid with a melting point of 80 oC. It is prepared by heating the ammonium salt of propanoic acid.
(a) (i) Write the equation for the reaction of propanoic acid with ammonia.
[1]
(ii) Write the equation for the decomposition of this ammonium salt to produce propanamide.
[1]
(b) The nmr spectrum of propanamide is shown below.
(i) The signal at 0 ppm is due to TMS. Explain why TMS is used as a standard.
[2]
(ii) Explain why the signal at 1.15 ppm is a triplet.
[1]
(iii) Explain why the signal at 2.25 ppm is a quartet.
[1]
Examiner Only
Marks Remark
8214.02R 15 [Turn over
(iv) Explain why the signal at 5.5 ppm is at the highest chemical shift in the spectrum.
[1]
(v) Explain three ways in which this spectrum would differ from the spectrum of the N-methylated compound, CH3CH2CONHCH3.
[3]
(c) The mass spectrum of propanamide is shown below.
20 30 40 50 60 70 80
100
80
60
40
20
0
m/e
% a
bund
ance
(i) Write the formulae of the fragment ions which have the following masses.
29 [1]
44 [1]
(ii) Explain what is meant by the term fragmentation.
[2]
(iii) Identify the base peak in the spectrum.
[1]
Examiner Only
Marks Remark
8214.02R 16
(d) The amide group is hydrolysed slowly with water, rapidly by acids and far more rapidly by alkalis.
(i) Write the equation for the reaction of propanamide with aqueous sodium hydroxide.
[2]
(ii) The relative reactivity may be explained by the reactive species present in the three reactions. Suggest why the hydroxide ion is a better reagent than the hydrogen ion to attack the amide group.
[1]
(e) Polyamides such as nylon are important industrial chemicals.
(i) Write an equation to show the formation of a section of the nylon molecule using the industrial monomers.
[3]
(ii) State two major uses of nylon.
[2]
Examiner Only
Marks Remark
8214.02R 17 [Turn over
(iii) Nylon is far more easily disposed of than polythene. Explain using the chemical structure of nylon why this is so and state how waste polythene is disposed of apart from recycling.
[4]
Quality of written communication [2]
Examiner Only
Marks Remark
8214.02R 18
14 Benzene, C6H6, was first isolated by Faraday in 1825. It is a colourless liquid with a melting point of 6 oC and a boiling point of 80 oC.
It is either represented by the Kekulé structure or by the more modern structure of a circle inside the ring.
Kekulé structure modern structure
(a) What is the empirical formula of benzene?
[1]
(b) What is the shape of benzene?
[1]
(c) Benzene may be catalytically reduced in several steps to cyclohexane using nickel.
(i) Write the overall equation for the reduction.
[1]
(ii) Draw a flow scheme showing the structure of all the reduction products.
[2]
(iii) Explain, in terms of chemisorption, the role of nickel in the reduction.
[3]
Examiner Only
Marks Remark
8214.02R 19 [Turn over
(d) The enthalpy of hydrogenation of cyclohexene is 2120 kJ mol21.
(i) What does this suggest for the value for the hydrogenation of benzene?
[1]
(ii) The actual hydrogenation value for benzene is 2208 kJ mol21. Suggest the reason for the difference.
[1]
(e) Draw a dot and cross diagram for the Kekulé structure of a benzene molecule using outer electrons only.
[3]
(f) Compare the reaction of bromine with benzene and ethene by drawing the following flow schemes:
(i) Draw a flow scheme to show the mechanism for the reaction of bromine with benzene.
[3]
(ii) Draw a flow scheme to show the mechanism for the reaction of bromine with ethene where Br1 is the electrophile.
[3]
Examiner Only
Marks Remark
8214.02R 20
(iii) Explain why there are different mechanisms for the reactions.
[2]
(g) Benzene is colourless but the solid pentacene is red.
pentacene
Explain why pentacene is coloured and benzene is not.
(ii) Zinc oxide is a catalyst [1] Conditions are high temperature [1] and pressure [1] [3] or finely divided catalyst or lack of air/oxygen
(iii) Hydrogen bromide [1]
(iv) Ammonia [1]
(b) (i) Primary amine [1] NH2 is attached to one carbon atom [1] [2] (ii) It is stronger [1] because the lone pair on nitrogen is more readily available (compared to phenylamine) [1] [2]
(c) (i) CH2CHNH2CH3
2 + H2SO4 SO4
CH2CHNH3CH3 +
2
2 _
[2]
(ii) Ionic salt is (more) soluble (than benzedrine) [1] or ionic salt is solid
(d) (i) Four different atoms/groups attached to a carbon atom [1]
(ii) One structure fits into the “enzyme” better than the other i.e. by a lock and key mechanism [1]
(e) (Drugs injected into GLC equipment and) pass through at different speeds/retention times [1] Each drug produces a distinct peak/retention time [1] [2] 21
– = 5Fe(COO)2 = 5Fe hence moles of Fe in 20 cm3 = 53 × 3.64 × 10–5 mol
= 6.067 × 10–5 mol
hence grams of Fe in 20 cm3 = 56 × 6.067 × 10–5 mol
= 3.397 × 10–3 g
in 100 cm3 of solution = 5 × 3.397 × 10–3 = 0.017 g
= 17 (mg) [4]
(d) (i) A central metal ion/atom, with ligands attached by coordinate bonds [2]
(ii) An ion or molecule ligand which uses two lone pairs of electrons to form two coordinate bonds with a central metal ion in a complex [2]
(iii) ox =
COO–
COO–Fe
ox
ox
ox
[2]
(iv) It is not superimposable on its mirror image/rotates the plane of plane polarised light [2]
(e) edta replaces the oxalate ions [1] there is an increase in entropy [1] [2] 25
8214.01 F 6 [Turn over
AVAILABLEMARKS
13 (a) (i) CH3CH2COOH + NH3 → CH3CH2COONH4 [1]
(ii) CH3CH2COONH4 → CH3CH2CONH2 + H2O [1] (b) (i) It only produces one signal (for the methyl groups) [1] which is out of the region for most proton spectra [1] [2]
(ii) The proton is next to a methylene/CH2 group [1]
(iii) The proton is next to a methyl/CH3 group [1]
(iv) The protons are next to nitrogen which is deshielding/ withdraws electrons [1]
(v) An extra peak [1] which would be below the quartet [1] The integration would show 3:2:1:3 [1] Some/all the peaks would change their chemical shift [1] To a maximum of [3] [3]
(c) (i) 29 C2H5+ [1]
44 CONH2+ [1]
(ii) (A positively charged ion produced when) the molecular ion [1] breaks apart [1] [2]
(iii) Base peak = 44 [1]
(d) (i) CH3CH2CONH2 + NaOH → CH3CH2COONa + NH3 [2] (ii) The hydroxide ion is attracted to the δ+ of the carbonyl group [1]
(e) (i) HOOC(CH2)4COOH + NH2(CH2)6NH2 → –OC(CH2)4CONH(CH2)6NH– + H2O [3] (ii) e.g. ropes/brushes/clothes [2]
(iii) Nylon is a polyamide/amide hence can be hydrolysed (to form the original molecules) Polythene cannot be hydrolysed (as it contains carbon–carbon bonds) hence it is either dumped or burned To a maximum of [4] [4]
Quality of written communication [2] 29
8214.01 F 7
AVAILABLEMARKS14 (a) CH [1]
(b) (Hexagonal and) planar/flat [1]
(c) (i) C6H6 + 3H2 → C6H12 [1]
(ii) No need for the presence of hydrogen
[2]
(iii) Adsorption on the surface/formation of bonds [1] Orientation of molecules/d-orbitals involved [1] Bonds weakened within reactants/bonds formed in products [1] [3]
(d) (i) –360 kJ [1]
(ii) Benzene is more stable/the bonds are delocalised/the bonds are not real double bonds [1]
(e)
C ××××C
CC
C
C
×
×H××
×H××××
H
××
×××× ××
×H
×H
×H
[3] (f) (i)
Br+ + H+
BrH Br
+
[3]
(ii) CH2 CH2 + Br+ → +CH2 CH2Br → CH2Br CH2Br
[3]
(iii) The double bonds in the benzene molecules are stable/ delocalised [1] electrons in the ethene double bond are more readily available [1] [2] (g) Pentacene has an extensively delocalised electron system [1] The energy levels are close together [1] Less energy is needed to raise the electrons to a higher level [1] Energy is thus in the visible region [1] Colours other than red are absorbed (by pentacene) [1] To a maximum of [4] [4] 25
Section B 100
Total 120
Br–
or
TIME2 hours.
INSTRUCTIONS TO CANDIDATESWrite your Centre Number and Candidate Number in the spaces provided at the top of this page.Answer all seventeen questions.Answer all ten questions in Section A. Record your answers by marking the appropriate letter on the answer sheet provided. Use only the spaces numbered 1 to 10. Keep in sequence when answering.Answer all seven questions in Section B. Write your answers in the spaces provided in this question paper.
INFORMATION FOR CANDIDATESThe total mark for this paper is 120.Quality of written communication will be assessed in Question 17(g).In Section A all questions carry equal marks, i.e. two marks for each question.In Section B the figures printed down the right-hand side of pages indicate the marks awarded to each question or part question.A Periodic Table of the Elements, containing some data, is included in this question paper.
9342
For Examiner’suse only
Question Number Marks
Section A1–10
Section B11121314151617
TotalMarks
Centre Number
Candidate Number
Chemistry
Assessment Unit A2 2assessing
Analytical, Transition Metals, Electrochemistryand Further Organic Chemistry
[AC222]TUESDAY 2 JUNE, AFTERNOON
ADVANCEDGeneral Certificate of Education
2015
*ac222*
AC
222
9342 2
Section A
For each of the following questions only one of the lettered responses (A–D) is correct.
Select the correct response in each case and mark its code letter by connecting the dots as illustrated on the answer sheet.
1 The chromatogram below was produced by two-way paper chromatography of a mixture of amino acids.
X
W
Z
Y
Solvent front 2
Solvent front 1
The table below gives the Rf values of some amino acids.
Amino acidRf values
Solvent 1 Solvent 2
Alanine 0.51 0.38
Asparagine 0.63 0.21
Isoleucine 0.44 0.72
Glycine 0.12 0.26
Lysine 0.18 0.14
Which one of the spots, W, X, Y or Z is glycine?
A W
B X
C Y
D Z
9342 3 [Turn over
2 Standard electrode potentials for two half-cells are shown below:
half-cell standard electrode potential/V
Ce31(aq) 1 3e2 ? Ce(s) 22.3
Th41(aq) 1 4e2 ? Th(s) 21.9
Which one of the following species is the most powerful reducing agent?
A Ce31(aq)
B Ce(s)
C Th41(aq)
D Th(s)
3 Which one of the following is not true for gas-liquid chromatography of a mixture?
A The liquid phase is mobile and the gas phase is stationary
B The molecules in the mixture have characteristic retention times
C The mixture is separated by partition between the liquid and the gas phase
D The percentage composition of the mixture can be determined
4 Which one of the following is the structure of terephthalic acid?
COOHCOOH
COOH
COOH
A B
COOH
HOOC
COOH
COOH
C D
9342 4
5 When carrying out an edta titration to find the concentration of calcium ions in a solution the solution is buffered to
A pH 4 and the colour change at the end point is blue to red.
B pH 4 and the colour change at the end point is red to blue.
C pH 10 and the colour change at the end point is blue to red.
D pH 10 and the colour change at the end point is red to blue.
6 Which one of the following is the weakest base?
A CH3CONH2
B C2H5NH2
C C6H5NH2
D NH3
7 The concentration of which one of the following solutions could be determined using colorimetry?
A Al31(aq)
B Ca21(aq)
C Fe31(aq)
D Zn21(aq)
8 Which one of the following is not true for glycine?
A It forms a blue solution with Cu2+(aq) ions
B It is optically active
C It reacts with sodium carbonate forming carbon dioxide
D It reacts with nitrous acid forming nitrogen
9342 5 [Turn over
9 How many p orbitals are involved in the delocalised π electrons of a benzene molecule?
A 2
B 3
C 6
D 12
10 Which one of the following is produced when CH3CONHCH3 is refluxed with excess dilute hydrochloric acid?
A CH3COOH and CH3NH2
B CH3COO2 and CH3NH31
C CH3COOH and CH3NH31
D CH3COO2 and CH3NH2
Examiner OnlyMarks Remark
9342 6
Section B
Answer all seven questions in this section
11 Vanadium is a typical transition metal.
(a) Explain, in terms of electronic configuration, what is meant by a transition metal.
[1]
(b) Vanadium has a variety of oxidation states.
(i) What is the electronic configuration of the V21 ion?
[1]
(ii) Complete the table below giving the formula, oxidation number and colour in solution of some vanadium ions.
ion oxidation number colour
V21 (aq)
yellow
VO21 (aq)
V31 (aq)
[4]
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9342 7 [Turn over
(c) Vanadium(V) oxide is used as a catalyst in the manufacture of sulfuric acid.
(i) Vanadium(V) oxide is a heterogeneous catalyst. Explain why it is described as heterogeneous.
[1]
(ii) Explain, in terms of chemisorption, how vanadium(V) oxide acts as a catalyst.
[3]
(iii) The vanadium(V) oxide converts sulfur dioxide to sulfur trioxide forming vanadium(IV) oxide, which then reacts with oxygen to re-form the vanadium(V) oxide. Write equations for these two reactions.
[2]
(iv) Complete the table below by naming the catalyst used for each industrial process.
industrial process catalyst
formation of ammonia
oxidation of ammonia
[2]
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9342 8
12 Phenylamine is involved in the manufacture of azo-compounds which can be used as dyestuffs.
(a) Phenylamine can be prepared from nitrobenzene according to the following flow scheme:
NH3Cl NH2NO2
A B
Name the reagents for steps A and B.
Step A [1]
Step B [1]
(b) Phenylamine is then converted to benzenediazonium chloride. Name the reagents and state the condition required to convert phenylamine to benzenediazonium chloride.
[2]
(c) Benzenediazonium chloride forms a yellow dye when coupled with dimethylaminobenzene.
N(CH3)2
dimethylaminobenzene
Write the equation for the reaction and circle the azo group.
[3]
Examiner OnlyMarks Remark
9342 9 [Turn over
(d) Quinine is fluorescent, it absorbs ultraviolet light and then emits it as visible light.
OCH3
N
OH
N
quinine
(i) How does the frequency of visible light differ from the frequency of ultraviolet light?
[1]
(ii) Quinine is optically active. Circle the carbon asymmetric centres on the above diagram.
[2]
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9342 10
13 (a) Benzene is more resistant than alkenes to reaction with bromine.
(i) What type of reaction do alkenes undergo with bromine?
[1]
(ii) Name a catalyst required for the reaction of benzene with bromine.
[1]
(iii) Draw a flow scheme to show the mechanism for the catalysed reaction of benzene with bromine.
[3]
(iv) Name the mechanism for the reaction of benzene with bromine.
[1]
(b) Toluene, C6H5CH3, can be nitrated in a similar way to benzene to form 2,4,6-trinitrotoluene.
(i) Suggest the structure of 2,4,6-trinitrotoluene.
[1]
(ii) Name the reagents used and write the equation for the formation of the nitronium ion.
Reagents:
Equation: [2]
Examiner OnlyMarks Remark
9342 11 [Turn over
14 Polyurethane products have a wide variety of uses including insoles in shoes and structural foams. Polyurethane is made in a two-step process.
(a) Step 1: Ethane-1,2-diol and hexanedioic acid are polymerised to form a polyester.
(i) What type of polymers are polyesters?
[1]
(ii) Draw a diagram of one repeating unit of the polyester.
[2]
(b) Step 2: The polyester is then reacted with a di-isocyanate forming an amide linkage.
CH3
NCO
NCO
di-isocyanate
Draw a diagram for the isocyanate group, –NCO, showing all the bonds present.
[1]
(c) Polyurethane foams are readily combustible and are a fire hazard producing carbon monoxide when burnt. Explain why carbon monoxide is poisonous.
[2]
(d) Explain why polyurethanes are biodegradable.
[1]
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9342 12
15 Putrescine is a foul smelling liquid produced by the breakdown of amino acids in dead organisms.
H2N(CH2)4NH2
putrescine
(a) (i) Suggest the systematic name for putrescine.
[1]
(ii) State why putrescine is soluble in water.
[1]
(b) Putrescine reacts in a similar way to ethylamine.
(i) Write an equation for the reaction of putrescine with excess nitrous acid.
[2]
(ii) Write an equation for the reaction of putrescine with excess ethanoyl chloride
[2]
(iii) Explain how the purified product formed between putrescine and excess ethanoyl chloride could be used to identify putrescine.
[2]
(c) Valine, CH3CH(CH3)CH(NH2)COOH, is an amino acid.
(i) Amino acids form zwitterions. What is a zwitterion?
[2]
(ii) Draw the zwitterion formed by valine.
[1]
Examiner OnlyMarks Remark
9342 13 [Turn over
(iii) Valine is optically active. Draw the 3D representations of the optical isomers.
[2]
(d) Amino acids combine to form proteins. Describe the structure of proteins under the following headings.
Primary:
Secondary:
Tertiary:
[3]
(e) Some enzymes formed by proteins are used in biological washing powders.
(i) Describe how enzymes act as catalysts.
[2]
(ii) Explain why biological washing powders do not work at high temperatures.
[2]
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9342 14
16 Nuclear magnetic resonance spectroscopy (nmr) is used to help understand the structure of molecules.
(a) TMS is the standard used in nmr.
(i) What is the chemical name for TMS?
[1]
(ii) Give two reasons why TMS is suitable for use as a standard in nmr.
[2]
(b) Sketch the nmr spectrum for methyl propanoate, CH3CH2COOCH3 showing the integration curve together with the splitting patterns. Indicate which hydrogen atoms are responsible for each peak.
TMS
[5]
Examiner OnlyMarks Remark
9342 15 [Turn over
(c) The mass spectrum for methyl propanoate is shown below.
100
80
60
40
20
0.00.0 20 40 60 80 100
rela
tive
inte
nsity
m/z
(i) What is the m/z value of the base peak?
[1]
(ii) Suggest the formulae of the species responsible for the peaks at 31 and 57.
31:
57: [2]
(iii) Explain why there is a peak at 89.
[1]
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9342 16
17 Chromium is purified in a number of steps after it is extracted from its ore.
Step 1: The impure chromium is heated with sodium carbonate in the presence of air to form sodium chromate(VI), Na2CrO4.
Step 2: The sodium chromate(VI) is converted to sodium dichromate which is then heated with carbon to form sodium chromate(III), Na2Cr2O4, and carbon monoxide.
Step 3: The Na2Cr2O4 is hydrolysed to form chromium(III) oxide. This is then reduced to chromium by aluminium.
(a) Write equations for the following reactions.
(i) The formation of sodium chromate(VI) in Step 1.
[2]
(ii) The formation of Na2Cr2O4 from sodium dichromate in Step 2.
[1]
(iii) The reduction of the chromium(III) oxide in Step 3.
[1]
(b) What is the colour change when sodium chromate(VI) is converted to sodium dichromate?
From: to [2]
(c) The oxygen atoms in the dichromate ion are arranged tetrahedrally around both chromium atoms. Draw a diagram below to suggest the 3D arrangement of the atoms in the dichromate ion.
[2]
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9342 17 [Turn over
(d) Acidified dichromate ions can be used to determine the concentration of iron(II) ions. The half-equations for the reaction are:
Cr2O722 1 14H1 1 6e2 → 2Cr31 1 7H2O
Fe21 → Fe31 1 e2
(i) Write a balanced ionic equation for the reaction between acidified dichromate and iron(II) ions.
[1]
(ii) Five iron tablets containing iron(II) sulfate, FeSO4, were dissolved in acid and the solution made up to 250 cm3 in a volumetric flask. 25.0 cm3 of this solution required 23.5 cm3 of 0.01 mol dm23 sodium dichromate solution for complete oxidation. Calculate the mass of iron(II) sulfate in an iron tablet.
[4]
(e) Chromium(III) ions form a range of complex ions with a variety of ligands.
(i) Explain what is meant by the term ligand.
[2]
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9342 18
(ii) The E–Z isomers of the complex ion [Cr(NH3)4Cl2]1 are shown below.
CrCI
CI
NH3
H3N
NH3
NH3
1
CrCI
NH3
H3N
NH3
CIH3N
1
Isomer 1 Isomer 2
Suggest and explain which structure is that of the E isomer and which is that of the Z isomer.
[3]
(f) The hydrated chromium(III) ions, [Cr(H2O)6]31, readily react with edta42 ions in a ligand replacement reaction.
(i) What term is given to ligands such as edta?
[1]
(ii) Write an equation for the reaction taking place between hydrated chromium(III) ions and edta4– ions.
[1]
(iii) Explain, in terms of entropy, why the reaction takes place.
[2]
9342 19
Examiner OnlyMarks Remark
(g) Chromium forms the double salt chrome alum. Describe, giving experimental details, how you would prepare crystals of chrome alum from potassium dichromate.
11 (a) An element which forms (at least one stable) ion with a partially filled d-subshell/An element which has an atom with a partially filled d-subshell [1]
(b) (i) 1s2 2s2 2p6 3s2 3p6 3d3 [1]
(ii) ion oxidation
number colour
+2 VioletVO2
+(aq) +5+4 Blue+3 Green
(error [–1]) [4] (c) (i) It is in a different (physical) state to the reactants [1]
(ii) Reactants adsorbed onto the surface [1] Reactant bonds weakened [1] Orientation of molecules [1] [3] (Do not accept comments on catalytic action)
(ii) H2N(CH2)4NH2 + 2CH3COCl → H3CCOHN(CH2)4NHOCCH3 + 2HCI
(2 marks, [–1] for each error) [2]
(iii) Find the melting point of the solid [1] Compare with data book/actual melting point [1] [2]
(c) (i) Molecule or ion which has a permanent positive and negative charge but which is neutral overall/ion which has permanent –NH3
+ and –CO2
– and is neutral overall [2]
(ii) CH3CH(CH3)CH(NH3+)COO– [1]
(iii)
C COOH
H
NH2CH3CH(CH3) (CH3)CHCH3
C
H
H2NHOOC
([–1] for each mistake) [2] (d) Primary: sequence of amino acids in the chain [1] Secondary: the twisting/coiling of the chain to form a -pleated sheet/ -helix by (intramolecular) hydrogen bonding [1] Tertiary: the bending/folding of the secondary structure to give a 3D shape held together by hydrogen bonding/disulfide bridges/ionic interactions [1] [3]
(e) (i) Enzymes have an active site [1] which provides a path of lower activation energy [1] [2]
(ii) Intramolecular forces are disrupted/broken [1] The enzymes will be denatured/structure disrupted by higher temperatures/the active site will no longer be effective [1] [2] 20
9342.01 F 7
AVAILABLEMARKS
16 (a) (i) Tetramethylsilane [1]
(ii) All the hydrogen atoms are equivalent [1] the signal is outside the usual range [1] TMS is inert/unreactive [1] to a maximum of [2] [2]
(b)
CH3O
CH2
CH3
3
2
3 TMS
Splitting of peaks [1] Each set of peaks [3] – correct heights, shift and label Integration curve above [1] [5]
(c) (i) 29 [1]
(ii) CH3O+ [1] CH3CH2CO+ [1] (penalise no charge once) [2]
(ii) Moles of Cr2O72– in 25 cm3 = (0.01 × 23.5)/1000 = 2.35 × 10–4
Moles of Fe2+ in 25 cm3 = (2.35 × 10–4) × 6 = 1.41 × 10–3
Moles of Fe2+ in 250 cm3 = 1.41 × 10–2 = 0.0141 Mass of FeSO4 in 250 cm3 = 0.0141 × 152 = 2.143 Mass of FeSO4 in one tablet = 2.143/5 = 0.429 g ([–1] for each mistake; [–1] if no mass unit) [4]
(e) (i) An ion or molecule with a lone pair of electrons which forms a coordinate bond with a (central) metal atom/ion in a complex [2]
(ii) Cl has a higher priority than N i.e. atomic number Cl > N [1] Isomer 1 has Cl on opposite sides [1] Isomer 1 is E [1] [3]
(f) (i) Polydentate/chelate/hexadentate [1]
(ii) [Cr(H2O)6 ]3+ + edta4– → [Cr(edta)]– + 6H2O [1]
(iii) More molecules/species on the right hand side [1] increases the entropy/disorder [1] [2]
(g) Cool a solution of potassium dichromate (Slowly) add concentrated sulfuric acid Add ethanol (slowly)(with stirring) Keep the temperature below 60 °C Leave to crystallise (and filter off crystals) [4]
Quality of written communication [2] 28
Section B 100
Total 120
TIME2 hours.
INSTRUCTIONS TO CANDIDATESWrite your Centre Number and Candidate Number in the spaces provided at the top of this page.Answer all seventeen questions.Answer all ten questions in Section A. Record your answers by marking the appropriate letter on the answer sheet provided. Use only the spaces numbered 1 to 10. Keep in sequence when answering.Answer all seven questions in Section B. Write your answers in the spaces provided in this question paper.
INFORMATION FOR CANDIDATESThe total mark for this paper is 120.Quality of written communication will be assessed in Question 17(g).In Section A all questions carry equal marks, i.e. two marks for each question.In Section B the figures printed down the right-hand side of pages indicate the marks awarded to each question or part question.A Periodic Table of the Elements, containing some data, is included in this question paper.
9342
For Examiner’suse only
Question Number Marks
Section A1–10
Section B11121314151617
TotalMarks
Centre Number
Candidate Number
Chemistry
Assessment Unit A2 2assessing
Analytical, Transition Metals, Electrochemistryand Further Organic Chemistry
[AC222]TUESDAY 2 JUNE, AFTERNOON
ADVANCEDGeneral Certificate of Education
2015
*ac222*
AC
222
9342 2
Section A
For each of the following questions only one of the lettered responses (A–D) is correct.
Select the correct response in each case and mark its code letter by connecting the dots as illustrated on the answer sheet.
1 The chromatogram below was produced by two-way paper chromatography of a mixture of amino acids.
X
W
Z
Y
Solvent front 2
Solvent front 1
The table below gives the Rf values of some amino acids.
Amino acidRf values
Solvent 1 Solvent 2
Alanine 0.51 0.38
Asparagine 0.63 0.21
Isoleucine 0.44 0.72
Glycine 0.12 0.26
Lysine 0.18 0.14
Which one of the spots, W, X, Y or Z is glycine?
A W
B X
C Y
D Z
9342 3 [Turn over
2 Standard electrode potentials for two half-cells are shown below:
half-cell standard electrode potential/V
Ce31(aq) 1 3e2 ? Ce(s) 22.3
Th41(aq) 1 4e2 ? Th(s) 21.9
Which one of the following species is the most powerful reducing agent?
A Ce31(aq)
B Ce(s)
C Th41(aq)
D Th(s)
3 Which one of the following is not true for gas-liquid chromatography of a mixture?
A The liquid phase is mobile and the gas phase is stationary
B The molecules in the mixture have characteristic retention times
C The mixture is separated by partition between the liquid and the gas phase
D The percentage composition of the mixture can be determined
4 Which one of the following is the structure of terephthalic acid?
COOHCOOH
COOH
COOH
A B
COOH
HOOC
COOH
COOH
C D
9342 4
5 When carrying out an edta titration to find the concentration of calcium ions in a solution the solution is buffered to
A pH 4 and the colour change at the end point is blue to red.
B pH 4 and the colour change at the end point is red to blue.
C pH 10 and the colour change at the end point is blue to red.
D pH 10 and the colour change at the end point is red to blue.
6 Which one of the following is the weakest base?
A CH3CONH2
B C2H5NH2
C C6H5NH2
D NH3
7 The concentration of which one of the following solutions could be determined using colorimetry?
A Al31(aq)
B Ca21(aq)
C Fe31(aq)
D Zn21(aq)
8 Which one of the following is not true for glycine?
A It forms a blue solution with Cu2+(aq) ions
B It is optically active
C It reacts with sodium carbonate forming carbon dioxide
D It reacts with nitrous acid forming nitrogen
9342 5 [Turn over
9 How many p orbitals are involved in the delocalised π electrons of a benzene molecule?
A 2
B 3
C 6
D 12
10 Which one of the following is produced when CH3CONHCH3 is refluxed with excess dilute hydrochloric acid?
A CH3COOH and CH3NH2
B CH3COO2 and CH3NH31
C CH3COOH and CH3NH31
D CH3COO2 and CH3NH2
Examiner OnlyMarks Remark
9342 6
Section B
Answer all seven questions in this section
11 Vanadium is a typical transition metal.
(a) Explain, in terms of electronic configuration, what is meant by a transition metal.
[1]
(b) Vanadium has a variety of oxidation states.
(i) What is the electronic configuration of the V21 ion?
[1]
(ii) Complete the table below giving the formula, oxidation number and colour in solution of some vanadium ions.
ion oxidation number colour
V21 (aq)
yellow
VO21 (aq)
V31 (aq)
[4]
Examiner OnlyMarks Remark
9342 7 [Turn over
(c) Vanadium(V) oxide is used as a catalyst in the manufacture of sulfuric acid.
(i) Vanadium(V) oxide is a heterogeneous catalyst. Explain why it is described as heterogeneous.
[1]
(ii) Explain, in terms of chemisorption, how vanadium(V) oxide acts as a catalyst.
[3]
(iii) The vanadium(V) oxide converts sulfur dioxide to sulfur trioxide forming vanadium(IV) oxide, which then reacts with oxygen to re-form the vanadium(V) oxide. Write equations for these two reactions.
[2]
(iv) Complete the table below by naming the catalyst used for each industrial process.
industrial process catalyst
formation of ammonia
oxidation of ammonia
[2]
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9342 8
12 Phenylamine is involved in the manufacture of azo-compounds which can be used as dyestuffs.
(a) Phenylamine can be prepared from nitrobenzene according to the following flow scheme:
NH3Cl NH2NO2
A B
Name the reagents for steps A and B.
Step A [1]
Step B [1]
(b) Phenylamine is then converted to benzenediazonium chloride. Name the reagents and state the condition required to convert phenylamine to benzenediazonium chloride.
[2]
(c) Benzenediazonium chloride forms a yellow dye when coupled with dimethylaminobenzene.
N(CH3)2
dimethylaminobenzene
Write the equation for the reaction and circle the azo group.
[3]
Examiner OnlyMarks Remark
9342 9 [Turn over
(d) Quinine is fluorescent, it absorbs ultraviolet light and then emits it as visible light.
OCH3
N
OH
N
quinine
(i) How does the frequency of visible light differ from the frequency of ultraviolet light?
[1]
(ii) Quinine is optically active. Circle the carbon asymmetric centres on the above diagram.
[2]
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9342 10
13 (a) Benzene is more resistant than alkenes to reaction with bromine.
(i) What type of reaction do alkenes undergo with bromine?
[1]
(ii) Name a catalyst required for the reaction of benzene with bromine.
[1]
(iii) Draw a flow scheme to show the mechanism for the catalysed reaction of benzene with bromine.
[3]
(iv) Name the mechanism for the reaction of benzene with bromine.
[1]
(b) Toluene, C6H5CH3, can be nitrated in a similar way to benzene to form 2,4,6-trinitrotoluene.
(i) Suggest the structure of 2,4,6-trinitrotoluene.
[1]
(ii) Name the reagents used and write the equation for the formation of the nitronium ion.
Reagents:
Equation: [2]
Examiner OnlyMarks Remark
9342 11 [Turn over
14 Polyurethane products have a wide variety of uses including insoles in shoes and structural foams. Polyurethane is made in a two-step process.
(a) Step 1: Ethane-1,2-diol and hexanedioic acid are polymerised to form a polyester.
(i) What type of polymers are polyesters?
[1]
(ii) Draw a diagram of one repeating unit of the polyester.
[2]
(b) Step 2: The polyester is then reacted with a di-isocyanate forming an amide linkage.
CH3
NCO
NCO
di-isocyanate
Draw a diagram for the isocyanate group, –NCO, showing all the bonds present.
[1]
(c) Polyurethane foams are readily combustible and are a fire hazard producing carbon monoxide when burnt. Explain why carbon monoxide is poisonous.
[2]
(d) Explain why polyurethanes are biodegradable.
[1]
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9342 12
15 Putrescine is a foul smelling liquid produced by the breakdown of amino acids in dead organisms.
H2N(CH2)4NH2
putrescine
(a) (i) Suggest the systematic name for putrescine.
[1]
(ii) State why putrescine is soluble in water.
[1]
(b) Putrescine reacts in a similar way to ethylamine.
(i) Write an equation for the reaction of putrescine with excess nitrous acid.
[2]
(ii) Write an equation for the reaction of putrescine with excess ethanoyl chloride
[2]
(iii) Explain how the purified product formed between putrescine and excess ethanoyl chloride could be used to identify putrescine.
[2]
(c) Valine, CH3CH(CH3)CH(NH2)COOH, is an amino acid.
(i) Amino acids form zwitterions. What is a zwitterion?
[2]
(ii) Draw the zwitterion formed by valine.
[1]
Examiner OnlyMarks Remark
9342 13 [Turn over
(iii) Valine is optically active. Draw the 3D representations of the optical isomers.
[2]
(d) Amino acids combine to form proteins. Describe the structure of proteins under the following headings.
Primary:
Secondary:
Tertiary:
[3]
(e) Some enzymes formed by proteins are used in biological washing powders.
(i) Describe how enzymes act as catalysts.
[2]
(ii) Explain why biological washing powders do not work at high temperatures.
[2]
Examiner OnlyMarks Remark
9342 14
16 Nuclear magnetic resonance spectroscopy (nmr) is used to help understand the structure of molecules.
(a) TMS is the standard used in nmr.
(i) What is the chemical name for TMS?
[1]
(ii) Give two reasons why TMS is suitable for use as a standard in nmr.
[2]
(b) Sketch the nmr spectrum for methyl propanoate, CH3CH2COOCH3 showing the integration curve together with the splitting patterns. Indicate which hydrogen atoms are responsible for each peak.
TMS
[5]
Examiner OnlyMarks Remark
9342 15 [Turn over
(c) The mass spectrum for methyl propanoate is shown below.
100
80
60
40
20
0.00.0 20 40 60 80 100
rela
tive
inte
nsity
m/z
(i) What is the m/z value of the base peak?
[1]
(ii) Suggest the formulae of the species responsible for the peaks at 31 and 57.
31:
57: [2]
(iii) Explain why there is a peak at 89.
[1]
Examiner OnlyMarks Remark
9342 16
17 Chromium is purified in a number of steps after it is extracted from its ore.
Step 1: The impure chromium is heated with sodium carbonate in the presence of air to form sodium chromate(VI), Na2CrO4.
Step 2: The sodium chromate(VI) is converted to sodium dichromate which is then heated with carbon to form sodium chromate(III), Na2Cr2O4, and carbon monoxide.
Step 3: The Na2Cr2O4 is hydrolysed to form chromium(III) oxide. This is then reduced to chromium by aluminium.
(a) Write equations for the following reactions.
(i) The formation of sodium chromate(VI) in Step 1.
[2]
(ii) The formation of Na2Cr2O4 from sodium dichromate in Step 2.
[1]
(iii) The reduction of the chromium(III) oxide in Step 3.
[1]
(b) What is the colour change when sodium chromate(VI) is converted to sodium dichromate?
From: to [2]
(c) The oxygen atoms in the dichromate ion are arranged tetrahedrally around both chromium atoms. Draw a diagram below to suggest the 3D arrangement of the atoms in the dichromate ion.
[2]
Examiner OnlyMarks Remark
9342 17 [Turn over
(d) Acidified dichromate ions can be used to determine the concentration of iron(II) ions. The half-equations for the reaction are:
Cr2O722 1 14H1 1 6e2 → 2Cr31 1 7H2O
Fe21 → Fe31 1 e2
(i) Write a balanced ionic equation for the reaction between acidified dichromate and iron(II) ions.
[1]
(ii) Five iron tablets containing iron(II) sulfate, FeSO4, were dissolved in acid and the solution made up to 250 cm3 in a volumetric flask. 25.0 cm3 of this solution required 23.5 cm3 of 0.01 mol dm23 sodium dichromate solution for complete oxidation. Calculate the mass of iron(II) sulfate in an iron tablet.
[4]
(e) Chromium(III) ions form a range of complex ions with a variety of ligands.
(i) Explain what is meant by the term ligand.
[2]
Examiner OnlyMarks Remark
9342 18
(ii) The E–Z isomers of the complex ion [Cr(NH3)4Cl2]1 are shown below.
CrCI
CI
NH3
H3N
NH3
NH3
1
CrCI
NH3
H3N
NH3
CIH3N
1
Isomer 1 Isomer 2
Suggest and explain which structure is that of the E isomer and which is that of the Z isomer.
[3]
(f) The hydrated chromium(III) ions, [Cr(H2O)6]31, readily react with edta42 ions in a ligand replacement reaction.
(i) What term is given to ligands such as edta?
[1]
(ii) Write an equation for the reaction taking place between hydrated chromium(III) ions and edta4– ions.
[1]
(iii) Explain, in terms of entropy, why the reaction takes place.
[2]
9342 19
Examiner OnlyMarks Remark
(g) Chromium forms the double salt chrome alum. Describe, giving experimental details, how you would prepare crystals of chrome alum from potassium dichromate.
11 (a) An element which forms (at least one stable) ion with a partially filled d-subshell/An element which has an atom with a partially filled d-subshell [1]
(b) (i) 1s2 2s2 2p6 3s2 3p6 3d3 [1]
(ii) ion oxidation
number colour
+2 VioletVO2
+(aq) +5+4 Blue+3 Green
(error [–1]) [4] (c) (i) It is in a different (physical) state to the reactants [1]
(ii) Reactants adsorbed onto the surface [1] Reactant bonds weakened [1] Orientation of molecules [1] [3] (Do not accept comments on catalytic action)
(ii) H2N(CH2)4NH2 + 2CH3COCl → H3CCOHN(CH2)4NHOCCH3 + 2HCI
(2 marks, [–1] for each error) [2]
(iii) Find the melting point of the solid [1] Compare with data book/actual melting point [1] [2]
(c) (i) Molecule or ion which has a permanent positive and negative charge but which is neutral overall/ion which has permanent –NH3
+ and –CO2
– and is neutral overall [2]
(ii) CH3CH(CH3)CH(NH3+)COO– [1]
(iii)
C COOH
H
NH2CH3CH(CH3) (CH3)CHCH3
C
H
H2NHOOC
([–1] for each mistake) [2] (d) Primary: sequence of amino acids in the chain [1] Secondary: the twisting/coiling of the chain to form a -pleated sheet/ -helix by (intramolecular) hydrogen bonding [1] Tertiary: the bending/folding of the secondary structure to give a 3D shape held together by hydrogen bonding/disulfide bridges/ionic interactions [1] [3]
(e) (i) Enzymes have an active site [1] which provides a path of lower activation energy [1] [2]
(ii) Intramolecular forces are disrupted/broken [1] The enzymes will be denatured/structure disrupted by higher temperatures/the active site will no longer be effective [1] [2] 20
9342.01 F 7
AVAILABLEMARKS
16 (a) (i) Tetramethylsilane [1]
(ii) All the hydrogen atoms are equivalent [1] the signal is outside the usual range [1] TMS is inert/unreactive [1] to a maximum of [2] [2]
(b)
CH3O
CH2
CH3
3
2
3 TMS
Splitting of peaks [1] Each set of peaks [3] – correct heights, shift and label Integration curve above [1] [5]
(c) (i) 29 [1]
(ii) CH3O+ [1] CH3CH2CO+ [1] (penalise no charge once) [2]
(ii) Moles of Cr2O72– in 25 cm3 = (0.01 × 23.5)/1000 = 2.35 × 10–4
Moles of Fe2+ in 25 cm3 = (2.35 × 10–4) × 6 = 1.41 × 10–3
Moles of Fe2+ in 250 cm3 = 1.41 × 10–2 = 0.0141 Mass of FeSO4 in 250 cm3 = 0.0141 × 152 = 2.143 Mass of FeSO4 in one tablet = 2.143/5 = 0.429 g ([–1] for each mistake; [–1] if no mass unit) [4]
(e) (i) An ion or molecule with a lone pair of electrons which forms a coordinate bond with a (central) metal atom/ion in a complex [2]
(ii) Cl has a higher priority than N i.e. atomic number Cl > N [1] Isomer 1 has Cl on opposite sides [1] Isomer 1 is E [1] [3]
(f) (i) Polydentate/chelate/hexadentate [1]
(ii) [Cr(H2O)6 ]3+ + edta4– → [Cr(edta)]– + 6H2O [1]
(iii) More molecules/species on the right hand side [1] increases the entropy/disorder [1] [2]
(g) Cool a solution of potassium dichromate (Slowly) add concentrated sulfuric acid Add ethanol (slowly)(with stirring) Keep the temperature below 60 °C Leave to crystallise (and filter off crystals) [4]
Quality of written communication [2] 28
Section B 100
Total 120
ADVANCEDGeneral Certificate of Education
2016
ChemistryAssessment Unit A2 2assessingAnalytical, Transition Metals, Electrochemistryand Further Organic Chemistry
[AC222]FRIDAY 10 JUNE, AFTERNOON
TIME2 hours.
INSTRUCTIONS TO CANDIDATESWrite your Centre Number and Candidate Number in the spaces provided at the top of this page.Answer all seventeen questions.Answer all ten questions in Section A. Record your answers by marking the appropriate letter on the answer sheet provided. Use only the spaces numbered 1 to 10. Keep in sequence when answering.Answer all seven questions in Section B. Write your answers in the spaces provided in this question paper.Do not write outside the boxed area on each page or on blank pages. Complete in blue or black ink only. Do not write with a gel pen.
INFORMATION FOR CANDIDATESThe total mark for this paper is 120.Quality of written communication will be assessed in Question 16(b)(ii).In Section A all questions carry equal marks, i.e. two marks for each question.In Section B the figures printed down the right-hand side of pages indicate the marks awarded to each question or part question.A Periodic Table of the Elements, containing some data, is included in this question paper.
*AC222*
*AC222*
*28AC22201*
*28AC22201*
Centre Number
Candidate Number
10136
*28AC22202*
*28AC22202*
10136
Section A
For each of the following questions only one of the lettered responses (A−D) is correct.
Select the correct response in each case and mark its code letter by connecting the dots as illustrated on the answer sheet.
1 Which one of the following shows alanine in the solid state?
A H2NCH2COOH
B H3N+CH2COO−
C H2NCH(CH3)COOH
D H3N+CH(CH3)COO−
2 Which one of the following is used to prevent the clotting of blood?
A Cisplatin
B Edta
C Iron(II)
D Iron(III)
3 Which one of the following factors determines the chemical shift in nuclear magnetic resonance spectroscopy?
A The chemical environment of hydrogen atoms
B The fragmentation of hydrogen atoms from the molecule
C The number of chemically equivalent hydrogen atoms
D The ratio of hydrogen atoms
*28AC22203*
*28AC22203*
10136[Turn over
4 In terms of the d sub-shell electronic configurations of ions which one of the following is not a transition metal?
A Chromium
B Copper
C Manganese
D Zinc
5 Given the following standard electrode potentials:
Ca2+ + 2e− ? Ca −2.87 V
Mn2+ + 2e− ? Mn −1.18 V
Zn2+ + 2e− ? Zn −0.76 V
Fe2+ + 2e− ? Fe −0.44 V
Fe3+ + e− ? Fe2+ +0.77 V
MnO4− + 8H+ + 5e− ? Mn2+ + 4H2O +1.51 V
which one of the following will reduce MnO4− to Mn2+ but not to Mn?
A Ca
B Fe2+
C Fe3+
D Zn2+
*28AC22204*
*28AC22204*
10136
6 Which one of the following describes the appearance of methyl 3-nitrobenzoate?
A Colourless liquid
B Cream solid
C Orange solid
D Violet crystals
7 Which one of the following is the number of isomeric secondary amines that have a relative molecular mass of 73?
A 1
B 2
C 3
D 4
8 Which one of the following is produced from the alkaline hydrolysis of propanamide?
A Ammonia
B Ammonium chloride
C Propanoic acid
D Water
*28AC22205*
*28AC22205*
10136[Turn over
9 Which one of the following is a feature of HD polythene?
A It has high crystallinity
B It has a highly branched structure
C It is highly flexible
D It is produced at very high pressure
10 Which one of the following will be observed in the nuclear magnetic resonance spectrum of pentan-3-one?
A One doublet and one triplet
B One triplet and one quartet
C Two doublets and two triplets
D Two triplets and two quartets
*28AC22206*
*28AC22206*
10136
Section B
Answer all seven questions in this section.
11 Complete the following table.
paper chromatography
thin-layer chromatography
gas-liquid chromatography
mobile phase solvent solvent
stationary phase water in paper oil on solid support
value recorded for analysis
retardation factor (Rf)
[4]
*28AC22208*
*28AC22208*
10136
12 Azo violet is a dye that can be formed from 4-nitrophenylamine via the 4-nitrobenzenediazonium ion.
N NO2N OH
HO
azo violet
(a) (i) Write the molecular formula for azo violet and calculate its relative molecular mass.
[2]
(ii) Calculate the mass of 4-nitrophenylamine (RMM = 138) required to produce 30 g of azo violet assuming a 60% yield.
[3]
*28AC22209*
*28AC22209*
10136[Turn over
(b) (i) Circle the azo group on the structure. [1]
(ii) Explain why azo violet is coloured.
[3]
(c) Draw the structure of the 4-nitrobenzenediazonium ion showing the bonds between the nitrogen atoms.
[2]
(d) State the names of the reagents and the reaction conditions for the formation of the 4-nitrobenzenediazonium ion from 4-nitrophenylamine.
[3]
*28AC22210*
*28AC22210*
10136
13 The standard electrode potential of copper can be determined by connecting a standard hydrogen electrode to a standard copper half-cell.
(a) Complete the labelling of the diagram below.
V
H2(g) at 1 atmosphere
Cu(s)
[4]
(b) The reaction of Cu2+ ions with I− ions produces insoluble copper(I) iodide.
2Cu2+(aq) + 4I−(aq) → 2CuI(s) + I2(aq)
What colour change will be observed in the solution during the reaction?
[2]
(c) Copper is commonly used in alloys such as brass. The following method describes how a titration can be carried out to determine the approximate percentage of copper in a sample of brass.
The copper in a 2.0 g sample of brass is oxidised to Cu2+ ions by reacting the brass with excess nitric acid.
Sodium carbonate solution is added to the mixture which is then diluted to 250 cm3 in a volumetric flask.
A 25.0 cm3 portion of this solution is transferred to a conical flask to which excess potassium iodide is added.
The liberated iodine is titrated against 0.1 mol dm−3 sodium thiosulfate solution.
*28AC22211*
*28AC22211*
10136[Turn over
(i) Suggest the purpose of the sodium carbonate solution.
[1]
(ii) Write an ionic equation for the reaction of thiosulfate ions with iodine.
[2]
(iii) Name the indicator used for the titration and state at what point it is added to the titration mixture.
[2]
(iv) What colour change takes place at the end point?
[1]
(v) 23.8 cm3 of 0.1 mol dm−3 sodium thiosulfate solution are required to react with the liberated iodine produced from a 25.0 cm3 portion of the solution. Calculate the percentage of copper in the sample of brass.
[4]
*28AC22212*
*28AC22212*
10136
14 A reaction scheme for [Cr(H2O)6]3+(aq) is shown below.
B
A
3+ [Cr(H2O)6 ] (aq)
process E process D
K2Cr2O7(aq)
5 cm3 NaOH(aq)
6 drops NaOH(aq)
excess en C
(a) (i) State the colour of solid A.
[1]
(ii) State the formula of solid A.
[1]
(b) State the colour of solution B.
[1]
(c) (i) State the formula of the complex ion C.
[1]
(ii) What is the coordination number of chromium in C?
[1]
*28AC22213*
*28AC22213*
10136[Turn over
(d) State the reagents required for process D.
[3]
(e) (i) Name the reducing agent and state the conditions used in process E.
[3]
(ii) Give the oxidation state of chromium before and after process E.
[1]
*28AC22214*
*28AC22214*
10136
15 (a) Nitrobenzene can be converted to 1,3-dinitrobenzene.
NO2
NO2
1,3-dinitrobenzene
(i) State the reagents required to convert nitrobenzene into 1,3-dinitrobenzene.
[2]
(ii) Name the nitrating species and write an equation for its formation.
[2]
(iii) Write a mechanism for the reaction of nitrobenzene to form 1,3-dinitrobenzene.
[3]
(iv) What is the name of the mechanism for the reaction?
[2]
*28AC22215*
*28AC22215*
10136[Turn over
(b) The 1,3-dinitrobenzene can then be converted to 1,3-diaminobenzene.
NH2
NH2
1,3-diaminobenzene
(i) State the reagents required to convert 1,3-dinitrobenzene to 1,3-diaminobenzene.
[2]
(ii) Explain why 1,3-diaminobenzene and ethane-1,2-diamine can act as bases.
[2]
(iii) Explain why 1,3-diaminobenzene is a weaker base than ethane-1,2-diamine.
[1]
*28AC22216*
*28AC22216*
10136
(c) Kevlar is a biodegradable polyamide that can be formed from 1,4-diaminobenzene and benzene-1,4-dicarboxylic acid.
OCC
OHHO
O
benzene-1,4-dicarboxylic acid
(i) Draw the repeating unit of Kevlar and circle the amide bond.
[2]
(ii) Give the structure of a reagent that could be used in place of benzene-1,4-dicarboxylic acid to make Kevlar.
[1]
(iii) Explain why Kevlar is biodegradable.
[2]
*28AC22218*
*28AC22218*
10136
16 Edta is a hexadentate ligand that reacts with a solution of copper(II) ions to produce a dark blue solution.
(a) Suggest the meaning of the term hexadentate.
[2]
(b) A solution of copper(II) ions reacts with edta according to the following equation.
[Cu(H2O)6]2+ + edta4− → [Cu(edta)]2− + 6H2O
(i) Explain, in terms of entropy, why the reaction between [Cu(H2O)6]2+ and edta takes place.
[2]
*28AC22219*
*28AC22219*
10136[Turn over
(ii) Describe how colorimetry can be used to prove that the ratio of copper(II) to edta in [Cu(edta)]2− is 1:1.
[5]
Quality of written communication [2]
*28AC22220*
*28AC22220*
10136
(c) Copper is used to catalyse the decomposition of gaseous propanone to ethenone, CH2 C O, and methane.
(i) Write an equation for the decomposition of propanone to ethenone and methane.
[1]
(ii) Explain and name the type of catalysis taking place.
[2]
(iii) Explain how transition metals catalyse reactions by chemisorption.
[3]
*28AC22222*
*28AC22222*
10136
17 Acrylamide is a carcinogen that gets into the body via cigarette smoke and some types of fried food. It is highly soluble in water and can be produced by heating the product from the reaction of propenoic acid with ammonia.
C C C
OHH
H NH2
propenoic acid NH3 ammonium salt heat
acrylamide
(a) (i) Draw the structure of propenoic acid showing all the bonds present.
[1]
(ii) Suggest the formula of the ammonium salt.
[1]
(iii) Suggest the name of the ammonium salt.
[1]
*28AC22223*
*28AC22223*
10136[Turn over
(b) Acrylonitrile can be made from acrylamide.
C C C N
HH
Hacrylonitrile
(i) Give the formula of the reagent used to convert acrylamide to acrylonitrile.
[1]
(ii) Name the type of reaction taking place.
[1]
(iii) With reference to the nmr spectra of both acrylamide and acrylonitrile, explain how nmr could be used to confirm the conversion of acrylamide to acrylonitrile was complete.
[2]
(c) Explain why acrylamide is soluble in water.
[2]
*28AC22224*
*28AC22224*
10136
(d) (i) State the expected observations when acrylamide is added to bromine water.
[1]
(ii) Write the equation for this reaction.
[1]
*28AC22225*
*28AC22225*
10136[Turn over
(e) Analysis of acrylamide levels is very important in the food industry. The mass spectrum of acrylamide is shown below.
40 50 60 70 80m/z
rela
tive
abun
danc
e
44
55
71
(i) Give two terms which describe the peak at m/z 71.
[2]
(ii) Explain why there is a peak at m/z 72.
[1]
*28AC22226*
*28AC22226*
10136
(iii) Give the ion responsible for the peak at m/z 44.
[1]
(f) Researchers suggest that the daily intake of acrylamide should not exceed 1.7 × 10−4 moles per kilogram of bodyweight. Calculate the mass of acrylamide, in milligrams, that should not be exceeded by an 80 kg man on a daily basis.
[3]
THIS IS THE END OF THE QUESTION PAPER
Periodic Table of the ElementsFor the use of candidates taking
Advanced Subsidiary and Advanced Level Chemistry Examinations
Copies must be free from notes or additions of any kind. No other type of data booklet or information
sheet is authorised for use in the examinations.
gce A/AS examinations
chemistry(advanced)
227
89
139
57
256
101
223
87
226
88
140
58
141
59
144
60
147
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
99
43
101
44
106
46
108
47
112
48
131
54222
86
210
85
210
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
2
40
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
1
1
* 58–71 Lanthanum series† 90–103 Actinium series
a = relative atomic mass (approx.)x = atomic symbolb = atomic number
THE PERIODIC TABLE OF ELEMENTSGroup
ab x
0VIIVIVIVIIIIII
*
†
One mole of any gas at 20 °C and a pressure of 1 atmosphere (105 Pa) occupies a volume of 24 dm3.Planck Constant = 6.63 × 10–34 J sGas Constant = 8.31 J mol–1 K–1
11 nitrogen/helium/inert gas (not gas on its own) silica/alumina Rf/retardation factor retention time/time or retention factor [4] 4
12 (a) (i) C12H9N3O4 [1] 259 [1] [2]
(ii) number of moles of azo violet = 30/259 = 0.116 60% → 100% 0.116/60 × 100 = 0.193 (1:1) number of moles of 4-nitrophenylamine = 0.193 mass of 4-nitrophenylamine = 0.193 × 138 = 26.63 g (units needed) [3]
(b) (i) N N circled [1]
(ii) extensive delocalisation (of electrons) and energy levels close together electrons excited/move to higher energy level
13 (a) Pt(s) or Platinum (solid)[1] 1 mol dm–3 H+ [1] 1 mol dm–3 Cu2+ [1] salt bridge [1] [4]
(b) blue to yellow/brown [2]
(c) (i) to neutralise (excess) HNO3 [1]
(ii) I2 + 2S2O32– → 2I– + S4O6
2– [2]
(iii) starch [1] added when mixture is straw coloured [1] [2]
(iv) blue-black to colourless [1]
(v) number of moles of S2O32– = (23.8 × 0.1)/1000 = 0.00238
(2:1) number of moles of I2 in 25 cm3 = 0.00119 number of moles of I2 in 250 cm3 = 0.0119 (1:2) number of moles of Cu2+ = 0.0238 mass of Cu = 0.0238 × 64* = 1.52 g % Cu = (1.52/2) × 100 = 76.16%/76% [4] 16 *Note that 63.5 can be used instead of 64
(b) (i) tin and concentrated hydrochloric acid [1] alkali/sodium hydroxide/ potassium hydroxide [1] [2]
(ii) both have a lone pair of electrons on the nitrogen [1] that can bond to a hydrogen ion [1] [2]
(iii) aromatic ring is electron withdrawing making the lone pair of electrons on nitrogen less available [1]
(c) (i)
N
H H O
N C
O
C [2]
(ii)
Cl Cl
CC
O O
[1]
(iii) contains an amide group/–CONH– [1] that can be hydrolysed by the action of microorganisms/bacteria [1] [2] 19
10136.01 F 6 [Turn over
AVAILABLEMARKS
16 (a) A ligand which uses six lone pairs to form six coordinate bonds with a central metal atom or ion in a complex [2]
(b) (i) 2 species → 7 species [1] increase in entropy [1] [2]
(ii) Select correct filter/appropriate wavelength [1] Prepare a range of samples consisting of different volumes/concentrations of Cu2+(aq) and edta solution [1] Record the absorbance of each sample [1] Plot a graph of the results [1] Peak on graph indicates the mixture that is in the correct ratio [1] [5]
Quality of written communication [2]
(c) (i) CH3COCH3 → CH2 C O + CH4 [1]
(ii) heterogeneous [1] different phases [1] [2]
(iii) reactants adsorb onto the surface [1] bonds weakened/broken in the reactants/orientation/closer together/lower activation energy [1] bonds form in products (and products are desorbed from the surface) [1] [3] 17
10136.01 F 7
AVAILABLEMARKS
17 (a) (i) H H
HC C
O
O
C
H
[1] (ii) CH2 CHCOONH4 [1]
(iii) ammonium propenoate [1]
(b) (i) P4O10 /P2O5 [1]
(ii) dehydration/elimination [1]
(iii) nmr spectrum of acrylamide has three peaks [1] nmr spectrum of acrylonitrile has two peaks [1] [2] hence spectrum changes (completely) from 3 peaks to 2 peaks
(c) hydrogen bonds [1] between lone pair of electrons on O of acrylamide and H of H2O (or between lone pair of electrons on O of H2O and H of NH2) [1] [2] (d) (i) orange solution decolourised [1]