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Advanced GCE A2 7882 - Past Papers

Oxford Cambridge and RSA Examinations GCEC hemistry Advanced GCE A2 7882 Advanced Subsidiary GCE AS 3882 Mark schemes for the Units January 2007 3882/ 7882 /MS/R/07J Oxford Cambridge and RSA Examinations OCR (Oxford Cambridge and RSA Examinations) is a unitary awarding body, established by the University of Cambridge Local Examinations Syndicate and the RSA Examinations Board in January 1998. OCR provides a full range of GCSE, A level, GNVQ, Key Skills and other qualifications for schools and colleges in the United Kingdom, including those previously provided by MEG and OCEAC.

CONTENTS Advanced GCE Chemistry (7882) Advanced Subsidiary GCE Chemistry (3882) MARK SCHEME ON THE UNITS Unit Content Page 2811 Foundation Chemistry 1

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Transcription of Advanced GCE A2 7882 - Past Papers

1 Oxford Cambridge and RSA Examinations GCEC hemistry Advanced GCE A2 7882 Advanced Subsidiary GCE AS 3882 Mark schemes for the Units January 2007 3882/ 7882 /MS/R/07J Oxford Cambridge and RSA Examinations OCR (Oxford Cambridge and RSA Examinations) is a unitary awarding body, established by the University of Cambridge Local Examinations Syndicate and the RSA Examinations Board in January 1998. OCR provides a full range of GCSE, A level, GNVQ, Key Skills and other qualifications for schools and colleges in the United Kingdom, including those previously provided by MEG and OCEAC.

2 It is also responsible for developing new syllabuses to meet national requirements and the needs of students and teachers. 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 marks were awarded by Examiners. It does not indicate the details of the discussions which took place at an Examiners meeting before marking commenced. 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.

3 Mark schemes should be read in conjunction with the published question Papers and the Report on the Examination. OCR will not enter into any discussion or correspondence in connection with this mark scheme . OCR 2007 Any enquiries about publications should be addressed to: OCR Publications PO Box 5050 Annersley NOTTINGHAM NG15 0DL Telephone: 0870 870 6622 Facsimile: 0870 870 6621 E-mail: CONTENTS Advanced GCE Chemistry ( 7882 ) Advanced Subsidiary GCE Chemistry (3882) mark scheme ON THE UNITS Unit Content Page 2811 Foundation Chemistry 1 2812 Chains and Rings 7 2813/01 How Far?

4 How Fast? / Experimental Skills 1 Written paper 13 2813/03 How Far? How Fast? / Experimental Skills 1 Practical Examination 19 2814 Chain, Rings and Spectroscopy 27 2815/01 Trend and Patterns 37 2815/02 Biochemistry 43 2815/04 Methods of Analysis and Detection 49 2815/06 Transition Elements 57 2816/01 Unifying Concepts in Chemistry/Experimental Skills 2 Written paper 63 2816/03 Unifying Concepts in Chemistry/Experimental Skills 2 Practical Examination 69 * Grade Thresholds 75 1 mark scheme 2811 January 2007 2811 mark scheme January 2007 2

5 Abbreviations, annotations and conventions used in the mark scheme / = alternative and acceptable answers for the same marking point ; = separates marking points NOT = answers which are not worthy of credit ( ) = words which are not essential to gain credit = (underlining) key words which must be used to gain credit ecf = error carried forward AW = alternative wording ora = or reverse argument Question Expected Answers marks 1 (a) (i) (atoms of) same element/same atomic with different numbers of neutrons/different masses 9 [1] (b) (i)

6 (ii) number of isotope percentage compositionprotons neutrons electrons 85Rb 71 to 73 37 48 37 87Rb 27 to 29 37 50 37 mark must add up to 100 9 ie 1 mark for each atomic structure; 1 for % compositions. Ar = (85 x 72) + (87 x 28)100 / 9 = 9 2nd mark for significant figures 71/29: = 73/27: = 9 9 [3] [2] (c) carbon-12/12C 9 [1] (d) atomic radii of Rb > atomic radii of elements above/ Rb has electrons in shell further from nucleus / Rb has more shells 9 Rb has more shielding 9 ( more is essential) (increased) nuclear charge is outweighed / despite increased nuclear charge.

7 By at least one of the factors above/ less attraction/ held less tightly 9 [3] (e) (i) (ii) Simplest (whole number) ratio of atoms/moles/elements 9 ratio Rb : Ag : I = : : or : : or 1 : 4 : 5 9 = RbAg4I5 9 [1] [2] Total: 13 2811 mark scheme January 2007 3 Abbreviations, annotations and conventions used in the mark scheme / = alternative and acceptable answers for the same marking point ; = separates marking points NOT = answers which are not worthy of credit ( ) = words which are not essential to gain credit = (underlining) key words which must be used to gain credit ecf = error carried forward AW = alternative wording ora = or reverse argument Question Expected Answers marks 2 (a) (i) (ii) (iii) 8-14 9 Ca(OH)2(aq) + CO2(g) CaCO3(s)

8 + H2O(l) 1st mark for species in equation 9 2nd mark for rest with st symbols 9 Allow H2O as either l or aq precipitate disappears/goes clear/goes colourless 9 Ca(HCO3)2 CaH2C2O6 9 [1] [2] [2] (b) (i) (ii) (iii) (iv) 1s22s22p63s23p6 9 3 9 10 9 dot-and-cross of Ca2+ with either 8 electrons or no electrons. 9 dot-and-cross of 2OH correct 9 H electron and Ca electrons can look the same. [1] [1] [1] [2] (c) (i) Heat CaCO3 9 CaCO3 CaO + CO2 9 Add water to CaO (or + H2O in equation) 9 CaO + H2O Ca(OH)2 9 [4] (d) neutralising (acid) soils/neutralising sewage/ softening water in water treatment/ neutralising acid water9 [1] Total: 15 2811 mark scheme January 2007 4 Abbreviations, annotations and conventions used in the mark scheme / = alternative and acceptable answers for the same marking point.

9 = separates marking points NOT = answers which are not worthy of credit ( ) = words which are not essential to gain credit = (underlining) key words which must be used to gain credit ecf = error carried forward AW = alternative wording ora = or reverse argument Question Expected Answers marks 3 (a) (i) (ii) attraction between oppositely charges ions 9 shared pair of electrons 99 shared electrons scores 1 mark only [1] [2] (b) (i) (ii) attraction of an atom/element for electrons 9 in a (covalent) bond/bonded pair 9 one element attracts bonded pair more /is more electronegative than other 9 on more electronegative atom and + on less electronegative element in example 9 May need to look for these marks in (c) if not given here.

10 [2] [2] (c) H bond shown between H of one molecule and O, N or F of another 9 H-bond shown going to a lone pair 9 [2] Total: 9 2811 mark scheme January 2007 5 Abbreviations, annotations and conventions used in the mark scheme / = alternative and acceptable answers for the same marking point ; = separates marking points NOT = answers which are not worthy of credit ( ) = words which are not essential to gain credit = (underlining) key words which must be used to gain credit ecf = error carried forward AW = alternative wording ora = or reverse argument Question Expected Answers marks 4 (a)


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