MARK SCHEME for the May/June 2006 question paper 9701 CHEMISTRY

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1 UNIVERSITY OF CAMBRIDGE INTERNATIONAL EXAMINATIONS GCE Advanced Level and GCE Advanced Subsidiary Level MARK SCHEME for the May/June 2006 question paper 9701 CHEMISTRY 9701/02 Paper 2 Maximum raw mark 60 This mark scheme is published as an aid to teachers and students, to indicate the requirements of the examination. It shows the basis on which Examiners were initially instructed to award marks. It does not indicate the details of the discussions that took place at an Examiners meeting before marking began. Any substantial changes to the mark scheme that arose from these discussions will be recorded in the published Report on the Examination. All Examiners are instructed that alternative correct answers and unexpected approaches in candidates scripts must be given marks that fairly reflect the relevant knowledge and skills demonstrated. Mark schemes must be read in conjunction with the question papers and the Report on the Examination. The minimum marks in these components needed for various grades were previously published with these mark schemes, but are now instead included in the Report on the Examination for this session. CIE will not enter into discussion or correspondence in connection with these mark schemes. CIE is publishing the mark schemes for the May/June 2006 question papers for most IGCSE and GCE Advanced Level and Advanced Subsidiary Level syllabuses and some Ordinary Level syllabuses.

2 Page 1 Mark Scheme Syllabus Paper 1 (a) (i) ammonia/nh 3 (ii) NH 4 + (iii) iron(ii) hydroxide/fe(oh) 2 [3] (b) barium sulphate/baso 4 [1] (c) (i) FeSO 4 (NH 4 ) 2 SO 4 (ii) FeSO 4 = (allow to 152) (NH 4 ) 2 SO 4 = (allow 132) (iii) xh 2 O = 392 ( ) = 108 x = 108 = 6 18 allow e.c.f. on candidate s sulphate in (c)(i) e.c.f. answer must be a whole number [6] [Total: 10]

3 Page 2 Mark Scheme Syllabus Paper 2 (a) x o H x oc x oc o xh x o [1] (b) n = PV = (1515 x 10 3 ) x (76 x 10-3 ) RT 8.31 x 298 = 46.5 [2] (c) (i) CaC 2 + 2H 2 O Ca(OH) 2 + C 2 H 2 (ii) n(c 2 H 2 ) = n(cac 2 ) =100 x 46.5 mass of CaC 2 = 100 x 46.5 x 64 = = g = kg (accept 298 kg) correct units necessary allow e.c.f. on candidate s answer in (b) [3] (d) C 2 H 2 (g) + 5 / 2 O 2 (g) 2CO 2 (g) + H 2 O(g) bonds broken: 2(H-C) 2 x 410 = 820 C C 840 = / 2 (O=O) 5 / 2 x 496 = kj mol -1 bonds made: 4(C=O) 4 x 740 = (O-H) 2 x 460 = kj mol -1 H comb = = -980 kj mol -1 allow e.c.f. on incorrect bonds made/broken [3] (e) (i) the enthalpy/energy change when one mole of a substance is burned in an excess of air/oxygen or completely combusted under standard conditions (ii) calculation in (d) includes H 2 O(g) whereas H comb involves H 2 O(l) or average bond energy terms are used in the Data Booklet [3] [Total: 12]

4 Page 3 Mark Scheme Syllabus Paper 3 (a) halogen colour physical state at room temperature chlorine green/yellow gas bromine orange/red liquid iodine black solid three colours correct three states correct [2] (b) (i) MgCl 2 white fumes/steamy fumes (of HCl) MgBr 2 red colour (of Br 2 ) or steamy fumes (of HBr) MgI 2 purple colour (of I 2 ) or black solid (I 2 ) or yellow solid (S) or stinking gas (H 2 S) (ii) MgCl 2 + H 2 SO 4 MgSO 4 + 2HCl allow MgCl 2 + 2H 2 SO 4 Mg(HSO 4 ) 2 + 2HCl [4] (c) (i) AgBr/silver bromide (ii) AgBr(s) + 2NH 3 (aq) Ag(NH 3 ) 2 Br(aq) equation (may be ionic) state symbols allow ecf on wrong halide in (i) [3] (d) (i) HCl no reaction HI purple vapour/black solid 2HI H 2 + I 2 (ii) bond energy in HCl is high bond energy in HI is lower/more easily broken (iii) hot glass rod provides activation energy [6] [Total: 15]

5 Page 4 Mark Scheme Syllabus Paper 4 (a) (i) BrCH 2 CHBrCH 2 OH (ii) CH 2 =CHCO 2 H (b) oxidation [2] [1] (c) structural or functional group isomerism [1] (d) step I CH 2 =CHCH 2 OH CH 3 CH 2 CH 2 OH H 2 Ni catalyst and heat or Pt at room temperature step II CH 3 CH 2 CH 2 OH CH 3 CH 2 CHO acidified dichromate(vi) heat not under reflux or distil off aldehyde as it is formed for both steps, conditions mark is only awarded if correct reagent is given [4] (e) both oxidation and reduction have occurred [1] (f) (i) HOCH 2 CHOHCH 2 OH formed CH 2 =CH- forms HOCH 2 CHOH - - CH 2 OH is unchanged (ii) HO 2 CCO 2 H [3] [Total: 12]

6 Page 5 Mark Scheme Syllabus Paper 5 (a) A reaction in which one atom or group of atoms replaces another. [1] (b) (i) C 2 H 5 Br + NaOH C 2 H 5 OH + NaBr allow OH - (ii) heat with aqueous NaOH/OH - [2] (c) (i) C 2 H 5 Br + KCN C 2 H 5 CN + KBr allow CN - or NaCN (ii) heat with KCN under reflux in ethanol [2] (d) (i) K is C 2 H 5 Cl/C 2 H 5 Br/C 2 H 5 I L is C 2 H 5 CN (ii) step I reagent - PCl 3 or PCl 5 or SOCl 2 or NaBr +conc H 2 SO 4 or P + Br 2 or P + I 2 conditions - room temperature or heat under reflux depending on reagent step III reagent - mineral acid conditions - heat under reflux for both steps, conditions mark is only awarded if correct reagent is given [6] [Total: 11]

MARK SCHEME for the November 2004 question paper 9701 CHEMISTRY

UNIVERSITY OF CAMBRIDGE INTERNATIONAL EXAMINATIONS GCE Advanced Subsidiary and Advanced Level MARK SCHEME for the November 2004 question paper 9701 CHEMISTRY 9701/02 Paper 2 (Structured Questions), maximum