Cambridge International Examinations Cambridge International Advanced Subsidiary and Advanced Level CHEMISTRY 970/4 Paper 4 A Level Structured Questions October/November 06 MARK SCHEME Maximum Mark: 00 Published 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 before 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 Report for Teachers. Cambridge will not enter into discussions about these mark schemes. Cambridge is publishing the mark schemes for the October/November 06 series for most Cambridge IGCSE, Cambridge International A and AS Level components and some Cambridge O Level components. IGCSE is the registered trademark of Cambridge International Examinations. This document consists of 6 printed pages. UCLES 06 [Turn over
Page Mark Scheme Syllabus Paper Cambridge International AS/A Level October/November 06 970 4 (a) (an element) forming (one or more stable) ions with incomplete d subshell [] (b)(i) co-ordination number oxidation number [Ni(CN) (NH 3 ) ] 4 + [CrCl (H O) 4 ] + 6 +3 (b)(ii) dative (covalent) / co-ordinate (b)(iii) correct diagram of [Ni(CN) (NH 3 ) ] or square planar or tetrahedral (c)(i) (concentrated) hydrochloric acid / soluble chloride ion (c)(ii) ligand exchange / substitution (d)(i) cis-trans (isomerism) / geometric(al) UCLES 06
Page 3 Mark Scheme Syllabus Paper Cambridge International AS/A Level October/November 06 970 4 (d)(ii) one 3D isomer one correct isomer other isomer correct in 3D 3 Total: UCLES 06
Page 4 Mark Scheme Syllabus Paper Cambridge International AS/A Level October/November 06 970 4 (a) NaN 3 Na +.5N (b) all atoms must have 8 outer electrons coding for electrons correct = 6 (0 5 ) central N must have 8 bonding electrons (inc. 5 and no non-bonded electrons) allow 3 (c)(i) (energy change) when mole of an (ionic) compound is formed or (energy change) when mole of an ionic solid/lattice/crystal is formed (from) gas (phase) ions / gaseous ions (under standard conditions) (c)(ii) forming an (ionic) bond UCLES 06
Page 5 Mark Scheme Syllabus Paper Cambridge International AS/A Level October/November 06 970 4 (c)(iii) use of H i 494 (kj mol - ) H o f = +07+494+4 73 H o f = + (kj mol - ) 3 (c)(iv) (ionic) radius / size of Na + is smaller (so stronger attraction to azide ion) OR ionic radius increases down the group Total: Question Answer Mark 3(a) Fe [Ar] 3d 6 4s Fe 3+ [Ar] 3d 5 3(b)(i) (catalyst is in) the same phase / state as the reactants 3(b)(ii) S O 8 + I SO 4 + I 3(b)(iii) (two) negatively-charged species repel each other 3(b)(iv) Equation : Fe 3+ + I Fe + + I Equation : S O 8 + Fe + SO 4 + Fe 3+ UCLES 06
Page 6 Mark Scheme Syllabus Paper Cambridge International AS/A Level October/November 06 970 4 3(c)(i) (entropy is a measure / degree of the) disorder of a system / substance 3(c)(ii) S o = ( 7) + (3 4) (90) (3 98) OR 696 684 S o = (+) (J K mol ) 3(c)(iii) G o = 43.6 (98 / 000) G o = 47. (kj mol ) 3(c)(iv) high E a and to speed up the rate Total: 3 UCLES 06
Page 7 Mark Scheme Syllabus Paper Cambridge International AS/A Level October/November 06 970 4 4(a) d orbitals split into lower and upper orbitals light / photon absorbed electron(s) promoted / excited / jumps up to (higher) (d ) orbital or electron(s) moves / jumps (from lower (d )) to higher (d ) orbital 3 4(b)(i) Cu + 4HNO 3 Cu(NO 3 ) + NO + H O or ionic Cu + 4H + + NO 3 Cu + + NO + H O correct species correct balancing 4(b)(ii) moles S O 3 - = 0..4 / 000 =.4 0 3 moles of Cu + in 5 cm 3 =.4 0 3 moles of Cu + in 50 cm 3 = =.4 0 mass of Cu =.4 0-63.5 =.44 g % Cu =.4 /.75 00 = 8. or 8.3% 4 Total: 9 UCLES 06
Page 8 Mark Scheme Syllabus Paper Cambridge International AS/A Level October/November 06 970 4 5(a) - + [HPO 4 ][H3O ] K a = [ HPO ] 4 5(b)(i) a solution that resists changes in ph when small amounts of acid and base / alkali are added 5(b)(ii) addition of acid: H + + HPO 4 H PO 4 OR H + + H PO 4 H 3 PO 4 addition of base: HO + H PO 4 HPO 4 + H O OR OH + HPO 4 H O + PO 4 3 5(c) [H + ] = 0 7.4 = 3.98 0 8 [HPO 4 ] / [H PO 4 ] = K a / [H + ] ([HPO 4 ] / [H PO 4 ]) = 6.3 0 8 / 3.98 0 8 =.58-.6 3 5(d)(i) HCl + H PO 4 H 3 PO 4 + Cl OR H + + H PO 4 H 3 PO 4 OR H O + H PO 4 H 3 PO 4 + OH UCLES 06
Page 9 Mark Scheme Syllabus Paper Cambridge International AS/A Level October/November 06 970 4 5(d)(ii) NaOH + HPO 4 PO 4 3 + H O + Na + OR OH + HPO 4 PO 4 3 + H O OR H O + HPO 4 PO 4 3 + H 3 O + Total: 0 6(a) O O * HO O Q O 6(b)(i) ratio of the concentration of a solute in the (two immiscible) solvents / liquids at equilibrium 6(b)(ii) K partition = (0.06 / 40) / (0.5 0.06 / 0) or reversed ratio: K partition = (0.5 0.06 / 0) / (0.06 / 40) K partition = 0.079 (0.0789) K partition =.7/3.0 UCLES 06
Page 0 Mark Scheme Syllabus Paper Cambridge International AS/A Level October/November 06 970 4 6(c) reagent structure of product(s) type of reaction excess Br (aq) addition of bromine to alkene Br substituted in phenol at positions and 6 (electrophilic) substitution or (electrophilic) addition NaBH 4 reduction (allow nucleophilic addition) UCLES 06
Page Mark Scheme Syllabus Paper Cambridge International AS/A Level October/November 06 970 4 excess hot NaOH(aq) hydrolysis + all three reaction types 6 6(d) mixture of (two) optical / stereo isomers formed Total: UCLES 06
Page Mark Scheme Syllabus Paper Cambridge International AS/A Level October/November 06 970 4 7(a)(i) electrophilic substitution 7(a)(ii) (Br + AlBr 3 ) Br + + AlBr 4 curly arrow from ring system to Br + correct intermediate curly arrow from C H bond into ring and loss of H + 4 7(b) both amide 7(c)(i) step, AlBr 3 and CH 3 Br OR other suitable halogen instead of Br step, KMnO 4 or potassium manganate(vii) step 3, conc. H SO 4 and conc. HNO 3 step 4. Sn and (conc.) HCl (heat) 4 UCLES 06
Page 3 Mark Scheme Syllabus Paper Cambridge International AS/A Level October/November 06 970 4 7(c)(ii) mark for each correct structure 3 7(d)(i) mark for each correct structure 7(d)(ii) reduction UCLES 06
Page 4 Mark Scheme Syllabus Paper Cambridge International AS/A Level October/November 06 970 4 7(e)(i) mark for each correct structure 7(e)(ii) 7(e)(iii) (precipitate) compound is less polar / more non-polar / non-ionic resulting in less hydrogen bonding to water Total: 0 UCLES 06
Page 5 Mark Scheme Syllabus Paper Cambridge International AS/A Level October/November 06 970 4 8(a) 0 0.34 = 3 (3.08) (0 3=70) and ( 5) + ( 0) = 70 OR F contains CO H = 45 so 0 45 = 57 so C 4 H 9 8(b)(i) correct = mark 3 correct = marks 8(b)(ii) -methyl butanoic acid 8(c)(i) O OH 8(c)(ii) δ/ppm environment of the carbon atom hybridisation of the carbon atom 7 alkyl / CH 3 sp 3 4 next to carboxyl / (CH 3 ) 3 C sp 3 79 carboxyl / CO H sp UCLES 06
Page 6 Mark Scheme Syllabus Paper Cambridge International AS/A Level October/November 06 970 4 8(d)(i) δ/ppm type of proton number of protons splitting 0.9 alkane / CH / CH 3 6 doublet.6 alkane / CH [multiplet].4 alkyl next to C = O / CH () CO / CH doublet.5 OH / CO H / carboxylic acid singlet 4 8(d)(ii) 8(e) CDCl 3 OR D O, DMSO, CD Cl, CCl 4 Total 3 UCLES 06