9701 CHEMISTRY. Mark schemes should be read in conjunction with the question paper and the Principal Examiner Report for Teachers.

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Margery Matthews
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1 CAMBRIDGE INTERNATINAL EXAMINATINS GCE Advanced Level MARK SCHEME f the May/June 04 series 970 CHEMISTRY 970/4 Paper 4 (Structured Questions), maximum raw mark 00 This mark scheme is published as an aid to teachers and candidates, to indicate the requirements of the examination. It shows the basis on which Examiners were instructed to award marks. It does not indicate the details of the discussions that took place at an Examiners meeting befe marking began, which would have considered the acceptability of alternative answers. Mark schemes should be read in conjunction with the question paper and the Principal Examiner Rept f Teachers. Cambridge will not enter into discussions about these mark schemes. Cambridge is publishing the mark schemes f the May/June 04 series f most IGCSE, GCE Advanced Level and Advanced Subsidiary Level components and some rdinary Level components.

2 Page Mark Scheme Syllabus Paper (a) (i) 4s d 4s 4s d 4s Fe d + Zn Fe + [] (ii) (colour due to absbance of visible light) due to electron promoted (from lower) to upper bital / energy level in Zn + there's no space in higher bital f the electron to go completely filled d-bitals / shell 4 (b) (i) yellow is due to [CuCl 4 ] reaction is ligand displacement / exchange (ii) (solution goes blue) due to [Cu(H ) 6 ] + blue ppt. (s) of Cu(H) [Cu(H ) 4 (H) ] etc. purple deep / dark blue solution (aq) due to [Cu(NH ) 4 ] + [Cu(NH ) 4 (H ) ] + (c) (i) KI + K S 8 K S 4 + I ionic: I + S 8 S 4 + I (ii) Fe + is a homogeneous catalyst (iii) equations: Fe + + S 8 Fe + + S 4 Fe + + I Fe + + I verbal equivalent, e.g. reactants are both negative ions, so repel each other Fe + can be oxidised by S 8 and Fe + can be reduced by I 7 [Total: 4]

3 Page Mark Scheme Syllabus Paper (a) A: voltmeter V potentiometer B: platinum Pt C: mol dm and H + HCl ( 0.5 M H S 4 ) D: lead (metal) Pb (b) (i) a in the box next to 0.7 V a comment that the [Pb + ] has decreased plus a description of the outcome, e.g. as [Pb + ] decreases (from mol dm ), Pb + (aq) + e Pb(s) goes over to the left hand side, as [Pb + ] decreases, Pb + is less likely to be reduced 4 (ii) (K sp =) [Pb + ][Cl ] (iii) if [PbCl ] =.5 0, [Pb + ] =.5 0 and [Cl ] = so K sp = (.5 0 ) (7.0 0 ) =.75 (.7) 0 4 mol dm 9 ([sf) + (c) (i) the (M + / M) E o f the two elements are very similar are 0. and 0.4 V E o (Sn 4+ / Sn + ) = 0.5 V and E o (Pb 4+ / Pb + ) =.69 V so Sn + is quite easily oxidised (to Sn 4+ ) is a stronger reductant Pb + is not easily oxidised (to Pb 4+ ) Pb 4+ is a stronger oxidant Pb 4+ is easily reduced (ii) e.g. PbCl + Zn Pb + ZnCl ( ionic) (other acceptable reductants: Fe, Mg, Ca but not Na K) Sn + + Sn (other acceptable oxidants: V +, Cr 7, Ag +, Cl,, F, Fe +, Mn 4 ) 5 (d) (i) Pb + (g) + Cl (g) PbCl (s) (ii) H f = H at + E(Cl Cl) + st IE + nd IE + E A (Cl) + LE 59 = LE LE = LE = 64 (kj mol ) [] (iii) LE(PbCl ) > LE(Pb ) me exothermic stronger lattice because Cl / chlide anion has smaller radius / size than / bromide 5 6 [Total: 0]

4 Page 4 Mark Scheme Syllabus Paper (a) (i) B and D + (ii) D (b) heat with dilute H + (aq) H S 4 (aq) (c) (i) K a larger than that f ethanol because the ethanoate ion / CH C is stabilised by charge delocalisation the H bond is weakened due to its proximity to C= / carbonyl group the second electronegative / oxygen atom K a smaller than that f chloethanoic acid because electron-withdrawing / electronegative chline (atom) makes the anion me stable H bond weaker H me easily lost (ii) [H + ] = ([CH C H] K a ) = ( ) =.() 0 (mol dm ) ph = log 0 [H + ] =.88 (.9) (d) (i) n(nah) at start = 0. 0/000 =.0 0 mol n(nah) at finish =.0 0 mol (ii) this is in 0 cm of solution, so [NaH] at finish =.0 0 / 0.00 =.() 0 mol dm ([ s.f.) ecf from (i) (iii) [H + ] = K w / [H ] = 0 4 /. 0 =.0 0 mol dm ph = log 0 [H + ] =.5() ph = log 0 (. 0 ) =.48 ph = pk w ph = 4.48 =.5() (iv) ph / vol curve: start at ph.88 (.9) ecf vertical (over at least ph units) ption at V = 0 cm levels off at ph.5 ± 0. ecf (v) indicat is thymolphthalein 4 7 [Total: 5]

5 Page 5 Mark Scheme Syllabus Paper 4. (a) (i) addition AND (ii) substitution (b) + Al + + Al 4 ( can use Al Cl FeCl Fe etc.) (c) (i) The two intermediate cations: H H CH CH etc (ii) The ring (of π electrons) in benzene is a stable configuration is unchanged after the reaction. (d) E is benzoic acid reaction : heat with KMn 4 (+ H H + ) reaction : heat with Cl + Al Cl FeCl (e) G is CCl Cl reaction : SCl PCl 5 reaction 4: LiAlH 4 [Total: ]

6 Page 6 Mark Scheme Syllabus Paper 5. (a) (i) Na reacts with H hydroxyl / alcohol groups (ii) Fehling's solution reacts with CH aldehyde groups (b) alkene C=C carbon double bond phenol phenylamine (c) CH CH CH(H)CH CH CH(H)CH CH HCH CH CH CH H CH CH H CH H + + (d) (i) the CH CH(H) group the CH C group methyl secondary alcohol methyl ketone (ii) CH CH(H)CH CH (e) (i) optical isomerism (ii) H H CH H H CH [Total: 0]

7 Page 7 Mark Scheme Syllabus Paper Section B 6. (a) (i) H NH NH H Peptide bond crect Rest of structure crect (skeletal, displayed structural fmula, a mix) (ii) Condensation nucleophilic substitution addition-elimination (iii) Water / H 4 (b) DNA Contains deoxyribose Contains thymine / T RNA Contains ribose Contains uracil / U Double strand / chain / helix two strands Single strand / chain [] (c) (i) (met) - leu - thr - pro - glu (ii) Mutations addition / insertion / deletion / substitution / replacement (of a base) (iii) Changing A ( the 4th base) into U [Total: 0]

8 Page 8 Mark Scheme Syllabus Paper 7 (a) (i) (Electrophesis): the size / shape / M r of the amino acid its charge (ii) (Paper chromatography): the partition of the amino acid between, the relative solubility of the compound in, the phases solvent / water and stationary phase / filter paper. (b) Use ninhydrin as a locating agent (c) The R f value retardation / retention fact the distance travelled by the acid compared to that travelled by a standard sample of the amino acid (d) R glutamic acid; S glycine; T lysine (e) W X U [Total: 0]

9 Page 9 Mark Scheme Syllabus Paper 8. (a) (i) Any addition polymer (e.g. polyethene, polypropene, polystyrene, PVC, PTFE, PVA, Teflon) (ii) Any condensation polymer (e.g. polyamide, polyester, nylon, Terylene, PET, PLA, Kevlar, Nomex) (b) Hydrolysis nucleophilic substitution Ester and amide / peptide C and CNH (c) CH CH Crect ester linkage CH side chain on only one monomer unit (d) Plant materials do not generally contain unsaturated hydrocarbons / alkenes / C=C (e) (i) Y van der Waals fces Z hydrogen bonding (ii) Z, because it can fm hydrogen bonds with water it contains polar C and NH groups [Total: 0]

9701 CHEMISTRY. Mark schemes should be read in conjunction with the question paper and the Principal Examiner Report for Teachers.

9701 CHEMISTRY. Mark schemes should be read in conjunction with the question paper and the Principal Examiner Report for Teachers. CAMBRIDGE INTERNATINAL EXAMINATINS GCE Advanced Level MARK SCHEME for the May/June 2014 series 9701 CHEMISTRY 9701/41 Paper 4 (Structured Questions), maximum raw mark 100 This mark scheme is published