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Paddington Academy AS-LEVEL PAPER 1 PP1 MS 1. (a) Proton: mass 1, charge + 1 (1) Neutron: mass 1, charge 0 (1) Electron mass 1/1840, charge -1 (1) Allow mass = 0, or negligible, or 1/1800 to 1/2000 Isotopes have the same number of protons (1) OR atomic number different number of neutrons (1) Isotopes have the same electronic configuration (1) OR same number of electrons Chemical properties depend on electrons (1) 7 (b) ×12 (1) OR × 12 or in words Spectrum gives (relative) abundance (1) OR % or amount And m/z (1) Multiply m/z by relative abundance for each isotope (1) Allow instead of m/z mass no, Ar or actual value from example Sum these values (1) Divide by the sum of the relative abundances (1) only award this mark if previous 2 given Max 2 if e.g. has only 2 isotopes 7 [14] 2. (a) (i) 0.00301/ 3.01 × 10–3; Penalise < 3sf in (a)(i); Allow 3.01 × 10–3 – 3.05 × 10–3. (for candidates who have used Mg as 24) (ii) 0.00602 Allow correct answer a(i) × 2. (iii) 0.00965/ 9.65 × 10–3; Allow 0.009646/ 0.0096-0.0097. (iv) 0.00363 moles; Allow range 0.0035 to 0.0037. Allow (a)(iii) – 2 (a)(ii) (must be positive). 1 1 1 1 Page 1 Paddington Academy (b) PV = nRT; Allow all capitals/ lower case. 1 V= ; M2 Mark is for all numbers correct. If units in answer are in dm3 allow this expression with 96 in denominator. 1 0.0132 m3/ 13.2 dm3; M3 Must have correct units/ allow 13200 cm3. Allow min 2 sig figs in answer. 1 (c) O = 69.6 (%); 1 2.17 : 4.35 Use of 7/8 CE then M1 only. 1 (1 : 2) NO2 Mark for formula not ratio. If NO2 and no working shown then allow 1 mark. If 69.6% + NO2 only = 2. Need to see evidence of M2 working. Allow M2 conseq on the wrong M1 (ie max 1). 1 [10] 3. (a) Iodine – molecular Not covalent lattice 1 Graphite – macromolecular/giant covalent/giant atomic 1 (b) Layers of (C atoms) 1 Connected by covalent bonds within each layer 1 Van der Waals forces/IMF between layers/weak forces between layers 1 Many/strong covalent bonds need to be broken If any other element mentioned other than C, CE = 0 Ignore the no of covalent bonds around the C if mentioned The first 3 marks could be scored with a labelled diagram. Need to label or state covalent bonds within the layers. Covalent or ionic or metallic bonds between molecules CE = 0 1 (c) Van der Waals forces are weak or easily broken Not vdw between atoms 1 Van der Waals between molecules (or implied) Allow weak IMF = 2 1 Page 2 Paddington Academy (d) Does not have delocalised/free electrons Only allow answer with respect to iodine Not all electrons used in bonding Ignore free ions 1 [9] 4. (a) They are elements (1) Ignore irrelevant comments (b) Enthalpy change (1) or heat energy change or heat change or ΔH or any named enthalpy change C.E. if change not mentioned Independent of route (1) OR depends on initial and final states Only give second mark if first mark awarded except allow if energy used instead of enthalpy 1 2 (c) ΔH = ΣΔHf (products) ‑ ΣΔHf (reactants) (1) (Or a cycle) = 2 × –242 + ½ × –394 – (–365) (1) (also implies first mark) = -316 kJ mol–1 (1) 3 Ignore no units penalise wrong units +316 scores 1/3 [6] 5. (a) (i) E + 3F → 2C + D (ii) mol-1dm3 (iii) (forward reaction is) exothermic or more products formed (i) Moles of iodine = 0.023 1 1 1 (b) 1 Moles of HI = 0.172 1 (ii) Kc = (iii) V cancels in Kc expression 1 1 (iv) Kc = 1 = 0.0179 or 1.79 × 10–2 1 (v) Kc = 55.9 or 56 Conseq i.e. (answer to (iv))–1 1 [10] Page 3 Paddington Academy 6. (a) Compound 1 If M1 incorrect, CE = 0 M1 1 No visible change with H2SO4 M2 1 Gives white ppt with NaOH M3 1 (b) BaCO3 1 The carbonate ion releases CO2 1 but the BaSO4 formed is highly insoluble. 1 (c) Compound 4 1 Sr(OH)2 + H2SO4 SrSO4 + 2H2O Allow ionic equation; ignore state symbols 1 [8] 7. (a) M1 Cl2 + 2Br− 2Cl− + Br2 Accept a correct equation using ½ Cl2 but no other multiples M2 solution goes orange / yellow ( from colourless) Ignore reference to brown colour Penalise incorrect observations eg fumes, precipitates 2 (b) M1 Cl2 + 2NaOH NaClO + NaCl + H2O (NaOCl) Or a correct ionic equation Ignore reference to “swimming pools” and to “disinfectant” M2 bleach or kills bacteria / bacteriacide / micro-organisms / microbes M3 sodium chlorate(I) ONLY (c) M Cl2 + H2O HClO + HCl (HOCl) Equilibrium symbol required in M1 Accept ionic RHS M2 The (health) benefit outweighs the risk or wtte OR a clear statement that once it has done its job, little of it remains OR used in (very) dilute concentrations / small amounts / low doses 3 2 Page 4 Paddington Academy (d) M1 Silver nitrate OR AgNO3 (with or without nitric acid) For M1 If only the formula is written then it must be correct If both the formula and the name are written then ignore incorrect attempt at the formula, but penalise an incorrect name M2 (depends on M1) white precipitate / white solid If the reagent is incomplete eg Ag+ ions, penalise M1 and mark on M3 Ag+ + Cl− AgCl Penalise both M1 and M2 for alkaline AgNO3 OR for the use of HCl to acidify the silver nitrate OR for Tollens’ reagent 3 [10] 8. D 9. D 10. C 11. D 12. B 13. B 14. D 15. B 16. C [1] [1] [1] [1] [1] [1] [1] [1] [1] 17. B [1] 18. D [1] 19. B 20. D [1] [1] Page 5