GCE Chemistry A H032/01: Breadth in chemistry Advanced Subsidiary GCE Mark Scheme for November 2020

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GCE Chemistry A H032/01: Breadth in chemistry Advanced Subsidiary GCE Mark Scheme for November 2020 Oxford Cambridge and RSA Examinations GCE Chemistry A H032/01: Breadth in chemistry Advanced Su... bsidiary GCE Mark Scheme for November 2020Oxford Cambridge and RSA Examinations OCR (Oxford Cambridge and RSA) is a leading UK awarding body, providing a wide range of qualifications to meet the needs of candidates of all ages and abilities. OCR qualifications include AS/A Levels, Diplomas, GCSEs, Cambridge Nationals, Cambridge Technicals, Functional Skills, Key Skills, Entry Level qualifications, NVQs and vocational qualifications in areas such as IT, business, languages, teaching/training, administration and secretarial skills. It is also responsible for developing new specifications to meet national requirements and the needs of students and teachers. OCR is a not-for-profit organisation; any surplus made is invested back into the establishment to help towards the development of qualifications and support, which keep pace with the changing needs of today’s society. 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. Mark schemes should be read in conjunction with the published question papers and the report on the examination. © OCR 2020Annotations Annotation Meaning Correct response Incorrect response Omission mark Benefit of doubt given Contradiction Rounding error Error in number of significant figures Error carried forward Level 1 Level 2 Level 3 Benefit of doubt not given Noted but no credit given IgnoreAbbreviations, annotations and conventions used in the detailed Mark Scheme (to include abbreviations and subject-specific conventions). Annotation Meaning DO NOT ALLOW Answers which are not worthy of credit IGNORE Statements which are irrelevant ALLOW Answers that can be accepted ( ) Words which are not essential to gain credit __ Underlined words must be present in answer to score a mark ECF Error carried forward AW Alternative wording ORA Or reverse argumentH032/01 Mark Scheme November 2020 SECTION A Question Answer Marks AO element Guidance 1 C 1 1.2 2 C 1 1.2 3 B 1 1.1 4 A 1 1.1 5 A 1 2.1 6 A 1 1.2 7 B 1 1.2 8 C 1 1.2 ALLOW 4 9 A 1 2.2 10 B 1 2.6 11 C 1 2.6 12 D 1 1.1 13 B 1 1.2 ALLOW 0.054(0) 14 A 1 1.2 15 C 1 1.1 16 C 1 1.1 17 A 1 1.2 18 C 1 2.8 ALLOW 36.7 19 B 1 1.2 20 C 1 2.6 Total 20H032/01 Mark Scheme November 2020 6 SECTION B Question Answer Marks AO element Guidance 21 (a) Shell 1st shell 2nd shell 3rd shell 4th shell Electrons 2 8 18 32 Requires all 4 numbers to be correct  1 1.1 (b) Differences: (Different number of) neutrons  Similarities: (Same number of) protons AND electrons  2 1.1×2 IGNORE different masses/mass numbers throughout (Question asks for atomic structures) ALLOW ‘amount’ for ‘number’ ALLOW ‘electron configuration’ for electrons (c) (i) FIRST CHECK ANSWER ON THE ANSWER LINE If answer = 35.48 (to 2 DP) award 2 marks (35 × 75.76) + (37 × 24.24) 100 OR 35.4848 OR 35.485  = 35.48 (to 2 DP)  2 1.2×2 For 1 mark: ALLOW ECF → to 2 DP if: • %s used with wrong isotopes ONCE OR • transposed decimal places for ONE % AND • calculated Ar is between 35 and 37 (c) (ii) m/z = 72: 35Cl37Cl OR Contains chlorine-35 AND chlorine-37 m/z values: 70 AND 74  2 3.1 3.2H032/01 Mark Scheme November 2020 7 Question Answer Marks AO element Guidance 22 (a) (i) (1s2)2s22p63s23p63d104s24p5  Look carefully at 1s22s22p63s23p6 – there may be a mistake 1 1.2 ALLOW 3d after 4s2, e.g. 1s22s22p63s23p64s23d104p5 ALLOW upper case D, etc and subscripts, e.g. …...4S23D1 DO NOT ALLOW [Ar] as shorthand for 1s22s22p63s23p6 IGNORE 1s2 repeated (a) (ii) P4 + 6Br2 → 4PBr3  1 2.6 ALLOW multiples (b) Giant ionic  In solid state/lattice, ions are fixed (in position) OR cannot move AND In liquid state, ions are mobile OR can move  2 1.1 1.2 ‘Giant’ is essential Mark independently of 1st structure mark IGNORE comments about electrons for solid IGNORE ‘free’ ionsH032/01 Mark Scheme November 2020 8 Question Answer Marks AO element Guidance (c) FIRST CHECK ANSWER LINES If molecular formula = BrF5 AND 174.6/175 AND working showing use of ideal gas equation Award 5 marks for calculation ---------------------------------------------------------------------- Rearranging ideal gas equation n = pV RT  Unit conversion AND substitution into n = pV RT : • R = 8.314 OR 8.31 • V = 76(.0) × 10–6 (m3) • T in K: 373 K e.g. 1.00 × 105 × 76.0 × 10–6 8.314 × 373  Calculation of n using p, V, R AND T n = 2.45 × 10–3 (mol)  Calculation of M M = 0.428 2.45 × 10–3 = 174.6  Molecular formula BrF5 OR F5Br  5 2.2×4 3.2 ALLOW ECF throughout IF n = pV RT is omitted, ALLOW when values are substituted into rearranged ideal gas equation. ALLOW conversion of V into dm3 AND p in kPa Gives same answer in powers of 10 Calculator value: from 8.314 = 2.450725899 × 10–3 from 8.31 = 2.45190555 × 10–3 IGNORE figures after 5 in 2.45 ALLOW ECF from a value of n that has been derived from pV = nRT e.g. 0.174.6 OR 0.175 from 2.45 ALLOW ECF matching ECF M from pV = nRT Use of 24 dm3 Final 2 marks possible for use of 76.0 cm3 OR 0.760 dm3 by ECF e.g. n = 76.0 24000 = 3.17 × 10–3 No mark (calculation much simpler) M = 0.428 3.17 × 10–3 = 135  ECF BrF3  ECFH032/01 Mark Scheme November 2020 9 Question Answer Marks AO element Guidance 23 (a) FIRST CHECK ANSWER ON THE ANSWER LINE If answer = 0.454 (mol dm–3) award 3 marks If answer = 0.227 (mol dm–3) award first 2 marks ---------------------------------------------------------------------- n(Ba(OH)2) in 100 cm3 1 mark = 3.89 171.3 = 0.0227…. (mol)  3 SF or more Concentration of OH– 2 marks n(Ba(OH)2) ×2 = 2 × 0.0227 = 0.0454…. (mol)  Use of ×10 = 10 × 0.0454 Concentration of OH– = 0.454 (mol dm–3)  3 SF required 3 3.1×2 3.2 ALLOW ECF throughout ALLOW use of 171 within working (Use of Ar: Ba 137 rather than 137.3) Calculator: 0.02270869819 IGNORE figures after 7 in 0.0227 ALLOW working with ×10 before ×2 Use of ×10 = 10 × 0.0227 = 0.227…. (mol)  Use of ×2 = 2 × 0.227 Concentration of OH– = 0.454 (mol dm–3)  3 SF required Common error 0.227 no × 2 2 marks (b) (i) (Titres that agree) within 0.1 cm3  1 2.3 ALLOW within 0.05 cm3 ALLOW ml for cm3 If cm3 units are absent, ASSUME cm3 BUT DO NOT ALLOW incorrect units, e.g. dm3; mol dm–3H032/01 Mark Scheme November 2020 10 Question Answer Marks AO element Guidance (b) (ii) FIRST CHECK ANSWER ON THE ANSWER LINE If answer = 0.0856 (mol dm–3) award 3 marks ---------------------------------------------------------------------- n(HNO3) = 0.160 × 26.75 1000 = 4.28 × 10–3 (mol)  n(Ba(OH)2) in 25.0 cm3 = 4.28 × 10–3 2 = 2.14 × 10–3 (mol)  Concentration = 2.14 × 10–3 × 1000 25 = 0.0856 (mol dm–3)  3 2.8×2 2.4 Use ECF throughout DO NOT ALLOW 4.3 × 10–3 BUT remaining marks available by ECF e.g. 4.3 × 10–3 ÷ 2 = 2.15 × 10–3  ECF 2.15 × 10–3 × 1000 25 = 0.086  ECF (c) Route 1 Reactant: Add water (to Ba) OR H2O in equation  Balanced equation: Ba + 2H2O → Ba(OH)2 + H2  Route 2 Balanced equation with O2 2Ba + O2 → 2BaO  Balanced equation with H2O BaO + H2O → Ba(OH)2  4 3.3 2.6 3.3 3.3 ALLOW multiples in equations Balanced equation automatically collects 2 marks for Route 1 ALLOW 1 mark for BOTH reactants in route 2: i.e. React with O2 AND then with H2O NOTE 3 correct balanced equations → 4 marksH032/01 Mark Scheme November 2020 11 Question Answer Marks AO element Guidance 24 (a) FIRST CHECK THE ANSWER ON ANSWER LINE If answer = –46 (kJ mol–1) award 3 marks Use of ∆cH values and balancing numbers ± (+180 + (3 × –286)) OR ± 678 AND ± (2 × –293) OR ± 586 seen anywhere  Correct subtraction using ∆H (–678) – (–586) = –92 (kJ mol–1)  Calculation of ∆fH(NH3) formation ∆fH(NH3) = –92 2 = –46 (kJ mol–1)  3 2.6 ×3 FULL ANNOTATIONS MUST BE USED ALLOW ECF throughout COMMON ERRORS –92 omission of ÷2 for ∆fH(NH3) 2 marks (+)46 Incorrect subtraction 2 marks (+)92 Incorrect subtraction & no ÷2 1 mark –385 no ×2 for –293 and no ÷2 1 mark –192.5 no ×2 for –293 2 marks (+)480 no ×3 for –286 and no ÷2 1 mark (+)240 no ×3 for –286 2 marks (+)187 no ×3 for –286 AND no ×2 for –293 AND no ÷2 1 mark (+)93.5 no ×3 for –286 AND no ×2 for –293 2 marks (b) Boltzmann distribution (seen anywhere) 2 marks Curve Curve starts close to origin (ALLOW flexibility) AND curve does not touch x axis at high energy  Labels (Number of) molecules/particles AND Energy  5 1.1×2 FULL ANNOTATIONS THROUGHOUT NOTE: Look for marking criteria within annotations on Boltzmann distribution diagram IGNORE slight inflexion on the curve IGNORE small increase at end of curve For labels, ALLOW kinetic energy IGNORE number of atoms IGNORE enthalpy for energyH032/01 Mark Scheme November 2020 12 Question Answer Marks AO element Guidance Curves for two temperatures 1 mark  Catalyst and activation energy 1 mark  Molecules and activation energy, Ea 1 mark Explanation At higher temperature OR in presence of catalyst More molecules/particles/collisions • have energy above activation energy OR have enough energy to overcome Ea  Could be shown on diagram(s) using shaded area with annotations 1.2×3 Temperature Drawing of two labelled curves AND higher temperature peak at higher energy AND lower on molecules IGNORE curves meeting at higher energy Higher temperature curve must cross over ASSUME that T2 is higher temperature than T1 Catalyst Ec shown at lower energy than Ea on Boltzmann distribution IGNORE catalyst provides a lower activation energy Boltzmann distribution not used ALLOW more molecules have energy to react ALLOW Ea for activation energy ALLOW Ec for activation energy with catalyst IGNORE more successful collisions OR collide more frequentlyH032/01 Mark Scheme November 2020 13 Question Answer Marks AO element Guidance 25 (a) 3 2.5×3 ALLOW any combination of skeletal OR structural OR displayed formula as long as unambiguous For repeat unit, • ‘side bonds’ required on either side of repeat unit from C atoms • DO NOT ALLOW > one repeat unit IGNORE brackets • IGNORE n ALLOW in either order (b) 1st curly arrow Curly arrow from double bond to Br of Br–Br  DO NOT ALLOW partial charge on C=C 2nd curly arrow Correct dipole on Br–Br AND curly arrow for breaking of Br–Br bond  4 1.2 1.2 ANNOTATE ANSWER For curly arrows, ALLOW straight or snake-like arrows and small gaps (see examples) ----------------------------------------------------------------- 1st curly arrow must • go to a Br atom of Br–Br AND • start from, OR be traced back to any point across width of C=C 2nd curly arrow must • start from, OR be traced back to, any part of δ+Br–Brδ– bond • AND go to Br δ–   H032/01 Mark Scheme November 2020 14 Question Answer Marks AO element Guidance 3rd curly arrow Correct carbocation with + charge on C with 3 bonds AND curly arrow from Br– to C+ of carbocation DO NOT ALLOW δ+ on C of carbocation OR  i.e. ALLOW carbonium + on either C atom Correct product to match mechanism  DO NOT ALLOW half headed or double headed arrows but allow ECF if seen more than once 2.5 2.5 3rd curly arrow must • go to the C+ of carbocation AND • start from, OR be traced back to any point across width of lone pair on :Br– • OR start from – charge on Br– ion (Lone pair NOT needed if curly arrow shown from – charge on Br–) ALLOW bromonium ion ALLOW any combination of skeletal OR structural OR displayed formula as long as unambiguous NOTE: For a mechanism with HBr, ALLOW all marks EXCEPT for final product (c) (i) (series of organic compounds with the) same functional group OR same/similar reactions / chemical properties  each successive member differs by CH2  2 1.1×2 IGNORE reference to physical properties IGNORE same general formula DO NOT ALLOW same empirical OR molecular formula Differs by CH2 is not sufficient (no successive) ALLOW differs by CH2 each time AW XH032/01 Mark Scheme November 2020 15 Question Answer Marks AO element Guidance (c) (ii) CnH2n–2  1 3.2 ALLOW CnH2(n–1) (c) (iii) Left-hand side, i.e. Reactants, balanced with 2Br2  Right-hand side, i.e. Product  2 2.5 2.6 ALLOW any combination of skeletal OR structural OR displayed formula as long as unambiguous ALLOW C3H4 for H3CC≡CH Questions asks only for structure of product ALLOW H3CCBr2CHBr2 OR H3CCBr2CBr2H (c) (iv) Any 2 structures from:   2 3.2×2 ALLOW any combination of skeletal OR structural OR displayed formula as long as unambiguous (c) (v)  1 2.5 ALLOW any combination of skeletal OR structural OR displayed formula as long as unambiguousOCR (Oxford Cambridge and RSA Examinations) The Triangle Building Shaftesbury Road Cambridge CB2 8EA OCR Customer Contact Centre Education and Learning Telephone: 01223 553998 Facsimile: 01223 552627 Email: general.qualifications@ocr.org.uk [Show More]

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