MARK SCHEME for the October/November 2014 series 9701 CHEMISTRY

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1 CAMBRIDGE INTERNATIONAL EXAMINATIONS Cambridge International Advanced Subsidiary and Advanced Level MARK SCEME for the October/November 204 series 970 CEMISTRY 970/23 Paper 2 (AS Structured Questions), maximum raw mark 60 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 204 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.

2 Page 2 Mark Scheme Syllabus Paper Cambridge International AS/A Level October/November (a) (i) increasing distance of (outer/highest energy) electron(s) from nucleus OR increasing distance of outer/valence shell from nucleus increased shielding / screening (from inner shells) reduces attraction (ii) increasing cation charge / effective nuclear charge OR decreasing number of electrons compared with protons [3] increase in attraction [2] (b) (boiling point) increases (down the group) increasing number of electrons (in molecules) down group increasing strength of / more van der Waals forces (allow correct alternatives to van der Waals forces) so more energy needed to overcome (the forces) [4] (c) (i) F I / IF 5 EF = MF or IF 5 = 222 [3] Cambridge International Examinations 204

3 Page 3 Mark Scheme Syllabus Paper Cambridge International AS/A Level October/November (ii) x x Cl xx xx I (Yes) as electronegativities are different (d) (i) W = NaClO; X = NaClO 3 ; Y = Cl; Z = AgCl (ii) 3Cl 2 + 6NaO 5NaCl + NaClO O M: correct species M2: balanced equation (iii) 0 to (0 to) +5 [2] [4] [2] [2] (iv) Ag + (aq) + Cl (aq) AgCl(s) [] [23] Cambridge International Examinations 204

4 Page 4 Mark Scheme Syllabus Paper Cambridge International AS/A Level October/November (a) C O CO [] (b) (c) Label on graph indicating catalysed and uncatalysed Ea OR statement Ea catalysed is lower (than Ea uncatalysed) owtte Reference to catalyst creating alternative mechanism / reaction pathway / route Idea that more molecules have sufficient energy (to react) so greater chance / frequency of successful collisions N angle = 07 o shape = (trigonal) pyramid(al) [4] [3] (d) (i) Advantage = higher rate Greater Kinetic Energy / speed / collision frequency / proportion of successful collisions Disadvantage reduced yield / less product / more reactants (Forward reaction) exothermic AND (hence in accordance with Le Chatelier s Principle) equilibrium / reaction shifts left (to counteract increasing temp) ora [4] pn3 (ii) Kp = 3 [] pn p Cambridge International Examinations 204

5 Page 5 Mark Scheme Syllabus Paper Cambridge International AS/A Level October/November (iii) N 2 (g) (g) 2N 3 (g) ( 0.8) (.6 3/2) xn 3 =.6/3.4 (= 0.47) xn 2 =.2/3.4 (= 0.353) x 2 = 0.6/3.4 (= 0.76) K p = (2 0 7 ) 2 = Pa (2 0 7 ) 3 + [5] [8] Cambridge International Examinations 204

6 Page 6 Mark Scheme Syllabus Paper Cambridge International AS/A Level October/November (a) P: C 3 C 2 C 2 C=C 2 Q: C 3 C 2 C=CC 3 R: C 3 C 2 C(C 3 )=C 2 S: C 3 C=C(C 3 ) 2 T: C 3 C 2 COC 3 (b) (i) (Different molecules with the) same (molecular and) structural formula different arrangements of atoms (in space) [5] [2] (ii) C C C C C trans-pent-2-ene C C C C C cis-pent-2-ene [2] (c) butan-2-ol [] [0] Cambridge International Examinations 204

7 Page 7 Mark Scheme Syllabus Paper Cambridge International AS/A Level October/November (a) reagent = conc 2 SO 4 or conc 3 PO 4 conditions = heat OR pass vapour over hot Al 2 O 3 reagent conditions [2] (b) (i) C 3 7 O + 2[O] C 2 5 CO O [] (ii) reagent = sodium / potassium dichromate or correct formula conditions = + / acidified and (heat under) reflux [2] (c) U = C 3 C(O)C 3 V = C 3 CBrC 3 OR U = C 3 C 2 C 2 O V = C 3 C 2 C 2 Br [2] (d) reagent = KO / NaO conditions = ethanol / alcohol AND eat / reflux [2] [9] Cambridge International Examinations 204

Cambridge International Examinations Cambridge International Advanced Subsidiary and Advanced Level. Published

Cambridge International Examinations Cambridge International Advanced Subsidiary and Advanced Level CHEMISTRY 970/22 Paper 2 AS Level Structured Questions October/November 206 MARK SCHEME Maximum Mark: