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

Size: px

Start display at page:

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

Kevin Francis
6 years ago
Views:

1 CAMBRIDGE INTERNATIONAL EXAMINATIONS Cambridge Advanced Subsidiary and Advanced Level MARK SEME for the March 06 series 970 EMISTRY 970/4 Paper 4 (A Level 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 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 March 06 series for most Cambridge IGCSE and Cambridge A and AS Level components. IGCSE is the registered trademark of Cambridge Examinations.

2 Page Mark Scheme Syllabus Paper Cambridge AS/A Level March Question Answer Mark (a) (b) sp x = 60 / C 60 H 60 (c) reaction : and UV light; reaction : Al 3, (NOT aqueous); (free) radical substitution C 3 C 3 or Cambridge Examinations 06

3 Page 3 Mark Scheme Syllabus Paper Cambridge AS/A Level March Question Answer Mark (a) Ca + (g) + (g) Ca (s) (state symbols required) Ca + (g) + (g) (+ e ) nd I.E of Ca st I.E of Ca EA of Atomisation/ H at of Ca E(-)/ H at of H latt o H f o Ca (s) H latt o = ( 349) = 58 kj mol 3 (b) (higher temperature means that) particles have more energy; entropy (of the gas / system) increases because of an increase in the amount of disorder / randomness; (c) reaction sign of S o CO(g) + O (g) CO (g) negative Mg(s) + ½O (g) MgO(s) negative CuSO 4 (s) + 5H O(l) CuSO 4.5H s O(s) negative NaHCO 3 (s) + H + (aq) Na + (aq) + CO (g) + H O(l) positive there is a reduction in the overall number of gaseous molecules (d) S o f = 386 (9 + (3 3)) = 99 (J K mol ) (e) G o = H o T S o = 7 ((98 75) / 000) = (+) (kj mol ) G o is positive and so the reaction is not spontaneous (at 98 K) Cambridge Examinations 06

4 PagP ge 4 MarM k Schemee Cambridge AS/AA LevL vel March 06 Syllabus 970 Paper 4 QuQ estion AnsA swer Markk 3 (a) Co Co o + [Ar] 3d3 7 4s [Ar] 3d3 7 s (b) Energy isolated ion tetrahedral complex (c) [Co( ) 3 (HH O) O 3 3] l Co H O OH H OH H ; H O Co l OH OH (d) [Pt( ) (NH3) 3 ] M, M: diagrams M3: names cis-platinn / cis-diamminedichloroplatinum( (II)) trans-platin / trans-diamminedichloroplatinum(ii) (e) (cis isomer) this can react / bond / bindd with DNA; which prevents replication of the strand / prevents cell division; M: formula M: units (ecf from formula) K stab = [Cu(N ) 4 (H O) [Cu(HO) + + ] 6 ][NH ] 4 mo ol 4 4 dm m (large value of K stab shows that) thee tetramminee complex is more stable Cambridge Examinations 06

5 PagP ge 5 MarM k Schemee Cambridge AS/AA LevL vel March 06 Syllabus 970 Paper 4 QuQ estion AnsA swer Markk 4 (a) st t order st t order rate = k[ O][ [OHH ] (iv) (v) (b) (c) (d) mo ol dm m 3 s calculation from candidate s answer to t (expected answer = 6) rate-determining both reactant species are in step / rater e-determining step acid / proton donor / acidicc behaviour nucleophilic addition step: step explanation: M: both curly arrows M: dipolee corrc rectly shown δ + δ (or per any suitable timee unit) Cambridge Examinations 06

6 Page 6 Mark Scheme Syllabus Paper Cambridge AS/A Level March Question Answer Mark 5 (a) any metal with an E o value more negative than 0.4 V, e.g. Fe, Mn, Zn, Mg, Cr, Al R: Li / Na / K / Ca / Ba M: value of E cell correctly calculated (with correct sign) for metal named in M: E o cell is positive and so reaction is feasible (b) M: (Cr O 7 + 4H + + 6e Cr H O) E o = +.33 V (H O + H + + e H O) E o = +.77 V E o cell = 0.44 (V) M: E o cell (0.44 V) is positive (so the reaction is feasible) / E o (Cr O 7 / Cr 3+ ) is less positive than E o (H O / H O) (c) M: Cr O 7 : ox.no Cr = +6 because = ox.no(cr) + (7 ) CrO 4 : ox.no Cr = +6 because = ox.no(cr) + (4 ) M: no change in oxidation number, so reaction is not redox (d) M: no. moles Cr deposited = 0.03 / 5 = moles M: deduction that 6 moles of e needed per mole of Cr / - reaction is Cr O 7 + 4H + + e Cr + 7H O M3: no. moles of e = = (0.5 t) / so t = ( ) / (0.5 60) = 46.3 min / 0.77 h / 780 s Cambridge Examinations 06

7 Page 7 Mark Scheme Syllabus Paper Cambridge AS/A Level March Question Answer Mark 6 (a) identity or value V nitrogen or chlorine 3 X NO / NO O / O 3 m, 3,,3, or 4 W sulfur Y SO or SO 3 n 4, 3 (b) M: (white precipitate is BaSO 4 ) descending the group H sol becomes more endothermic / positive; M, M3 any two from: H latt decreases / becomes more endothermic / becomes less exothermic H hyd decreases / becomes more endothermic / becomes less exothermic H hyd decreases more than H latt Cambridge Examinations 06

8 PagP ge 8 MarM k Schemee Cambridge AS/AA LevL vel March 06 Syllabus 970 Paper 4 QuQ estion AnsA swer Markk 7 (a) M: phenol is i more acidic than ethanol because the O H bond in phenol is weakenedd / thet phenoxide anion is stabilised / ethanol has an elee ctron donating group M: p orbital / lone pairr off electronss on O can bee delod ocalisedd over / overlapss with ring reagent conditions Structure 3 HNO O 3 dilute, 5 C Br aqueous (I: temperature) electrophilic substitution (b) white precipitate / solidd between 0 C and 0 C M: double bonb nd between nitrogenn atoms M: rest of mom lecule N N OHH (c) C C H NHN N 3 3 either onee or both 3 3 g roups circledd Cambridge Examinations 06

9 PagP ge 9 MarM k Schemee Cambridge AS/AA LevL vel March 06 Syllabus 970 Paper 4 QuQ estion AnsA swer Markk 8 (a) P Q R amidee ketone secondary alcohol Q = carbonyl and R = alcohol scores [] (b) (c) see line on diad gram inn (b) (d) reagent observation 3 alkalinee iodine solution yellow ppt. formed universal indicatorr blue / purplee colour formed,4-dinitrophenylhydrazine yellow / orangee ppt formed Tollens reagent no reaction (e) LiAl H H 4 (must be skeletal) C OH Cambridge Examinations 06

10 Page 0 Mark Scheme Syllabus Paper Cambridge AS/A Level March Question Answer Mark 9 (a) polyester : Terylene / polylactic acid (PLA) / polyamide : nylon / Kevlar / Nomex water or hydrochloric acid / hydrogen chloride (b) polymer biodegradable A yes B yes C no D yes HO OH and or equivalent,4-diacyl chloride or equivalent,4-diester (c) V: it has two amine / NH groups (which can be protonated) or it has an amine / NH group on its side chain / R group four (TT, TU, UT, UU) hydrogen bonds; between the O / N atoms or named group (in the polypeptide) and water; or ion-dipole attractions; between N + / CO and water; Cambridge Examinations 06

9701 CHEMISTRY. 9701/12 Paper 1 (Multiple Choice), maximum raw mark 40

9701 CHEMISTRY. 9701/12 Paper 1 (Multiple Choice), maximum raw mark 40 CAMBRIDGE INTERNATIONAL EXAMINATIONS Cambridge International Advanced Subsidiary and Advanced Level MARK SCHEME for the March 206 series 970 CHEMISTRY 970/2 Paper (Multiple Choice), maximum raw mark 40