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

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1 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: 60 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 206 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 8 printed pages. UCLES 206 [Turn over

2 Page 2 Mark Scheme Syllabus Paper Cambridge International AS/A Level October/November (a) 0.04 OR (b)(i) Na 2 CO 3 + 2HCl 2NaCl + CO 2 + H 2 O (b)(ii) OR (b)(iii) OR (b)(iv) 0.05 OR (b)(v) OR (b)(vi) OR OR 0.03 OR (b)(vii) 40 Ca / calcium Total: 9 UCLES 206

3 Page 3 Mark Scheme Syllabus Cambridge International AS/AA Level October/November Paper 22 Question Answer Mark 2(a) Arrow vertically up from N 2 O 4 line to 2NO 2 line labelled enthalpy change / H Arrow vertically up from N 2 O 4 line to dashed line from peak labelledd activation energy / E a 2(b)(i) M r = m R T p V = = (b)(ii) 2n 2(b)(iii) 0.05 n + 2n OR n 2(b)(iv) 2n ( n) 2(b)(v) N 2 O 4 = NO 2 = (b)(vi) K p = pno 2 pn 2 O 4 UCLES 206

4 Page 4 Mark Scheme Syllabus Paper Cambridge International AS/A Level October/November (b)(vii) ( ) 2 /( ) OR / OR 44.8 Pa OR kpa Total: 3 3(a)(i) 3(a)(ii) 3(a)(iii) Increasing nuclear attraction Increasing nuclear charge / number of protons AND constant / similar shielding / same shell From 2 / Mg to 3 / Al: (Outer) electron in 3 / Al in (3)p (whereas outer electron in 2 / Mg in (3)s) (3p =) higher energy level / more shielded From 5 / P to 6 / S electron repulsion ( 6 / S has a) pair of electrons in a (3)p orbital / a (3)p orbital is full ORA (decreasing IE down Group 0) due to decreasing nuclear attraction increasing shielding / increasing number of shells / energy levels / increasing distance of (outer) electrons (from nucleus) UCLES 206

5 Page 5 Mark Scheme Syllabus Paper Cambridge International AS/A Level October/November (b)(i) 3(b)(ii) 3(b)(iii) Increasing strength of / more energy needed to break (metallic) bonding / increasing strength of attraction between (cat)ion / nucleus and delocalised / free / sea of / cloud of electrons Increasing number of delocalised electrons / decreasing (cat)ion size / increasing charge / charge density of (cat)ion Attraction for electrons too strong to fully delocalise all 3 in Al OR difference in size between 2/Mg 2+ and 3/Al 3+ is less than difference in size between /Na + and 2/Mg 2+ OR magnitude of increase in charge is less from 2+ to 3+ than from + to 2+ Increase (5 / P to 6 / S) then decrease (to 7 / Cl and 8 / Ar) OR general decrease (from 5 / P to 8 / Ar) with an increase from 5 / P to 6 / S OR S (8) >P (4) >Cl (2) >Ar (melting point depends on strength of) VdW / IMFs The greater the number of electrons in the molecule (atom for Ar) the greater the strength of VdW / IMFs OR the greater the melting point ora 3(b)(iv) Giant covalent (structure) / many (strong) covalent bonds (need breaking) Total: 5 UCLES 206

6 Page 6 Mark Scheme Syllabus Paper Cambridge International AS/A Level October/November (a)(i) 2 bromobutane 4(a)(ii) e.g. of mirror images CH 3 CH 3 C H C H H 3 CCH 2 Br Br CH 2 CH 3 + 4(a)(iii) e.g. of swapped groups CH 3 CH 3 C H C Br H 3 CCH 2 Br H 3 CCH 2 H CH 3 CH 2 CH 2 CH 2 Br (CH 3 ) 2 CHCH 2 Br (CH 3 ) 3 CBr 4(b)(i) 3-bromo-3-ethylpentane 4(b)(ii) H 3 C CH 2 δ+ δ H 3 C CH 2 C Br C H 3 H 3 CCH 2 CH 2 H 3 CCH 2 H 3 CCH - 2 HO M = dipole and curly arrow from bond to (or just beyond) Br M2 = correct carbocation M3 = OH with curly arrow from lone pair on O to C(+) C + 4(b)(iii) S N / nucleophilic substitution UCLES 206

7 Page 7 Mark Scheme Syllabus Paper Cambridge International AS/A Level October/November (c)(i) Sodium / potassium hydroxide Ethanol / alcohol AND heat 4(c)(ii) elimination 4(c)(iii) Total: 7 UCLES 206

8 Page 8 Mark Scheme Syllabus Paper Cambridge International AS/A Level October/November (a)(i) Cl and CH 3 5(a)(ii) Cl and + CH 3 / CH 3 + 5(b)(i) Oxidation OR reduction 5(b)(ii) Condensation 5(b)(iii) Reduction OR oxidation OR addition 5(b)(iv) Addition Total: 6 UCLES 206