Marks

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1. (i) atoms of the same element with different numbers of neutrons/different masses (1) 1 (ii) 79Br 35 protons, 44 neutrons, 35 electrons (1)
81Br 35 protons, 46 neutrons, 35 electrons (1) 2 (iii) (1s2)2s22p63s23p63d104s24p5 (1) 1 [4]

2. (i) iodide has been converted to iodine (1)
(with correct use and spelling of iodide and iodine)
The 1st experiment shows that bromine is more reactive than iodine (1)
The 2nd experiment shows that chlorine is more reactive than bromine (1)
Accept 1 mark for 2nd and 3rd marking points if the correct reactivity order of chlorine > bromine > iodine has been stated. 3 (ii) Br2 + 2I–  2Br– + I2 (1) 1 [4]

3. add AgNO3/Ag+ (to a solution of the food) (1)
Ag+(aq) + Cl–(aq)  AgCl(s) (1) degree of cloudiness/whiteness/intensity indicates relative quantity (1) sodium ion content needs to be determined as well (1) [4]

4. (i) S (1) 1 (ii) Al (1) 1 (iii) B (1) 1 (iv) Ca (1) 1 (v) K (1) 1 (vi) K (1) 1 [6]

5. (i) atomic radii decrease /similar shielding /electrons added to same shell (1) number of protons in the nucleus increases (1) nuclear attraction increases (1) 3 (ii) Na2+(g)  Na3+(g) + e– : equation and state symbols (1) 1 (iii) large jump (in energy) between the 4th and 5th ionisation energies (1) four electrons in outer shell so element is Si (1) 2 [6]

6. (i)

positive ions (1) electrons (1) (must be labelled) 2 (ii) the electrons move (1) 1 [3]

7. (i) attraction between oppositely charged ions 1 (ii)

Mg and Cl both with 8 electrons in outer shell, (accept 0 electrons for Mg)
Cl must have one dot to seven crosses or vice versa (1) correct charges on each ion (1) 2 (iii) MgCl2 does not conduct when solid because ions are fixed in lattice (1)
H2O does not conduct as there are no free charge carriers/water molecules are uncharged (1)
MgCl2 conducts when aqueous because ions are free to move (1) 3 [6]

8. To boil Cl2, van der Waals’ forces/intermolecular forces are broken
(with van der Waals/intermolecular spelt correctly) (1)
To boil C, covalent bonds are broken (1) covalent bonds are stronger than van der Waals’ forces (1) [3]

9. removed for test

10. removed for test [3]

11. (i) because Ca has changed from 0 to +2 (1) and H has changed from +1 to 0 (1) 2 (ii) Calcium reacts with water producing hydrogen/H2/calcium/hydroxide/Ca(OH)2 (1) (i.e. one product)
Ca(s) + H2O(l)  Ca(OH)2(aq) + H2(g) (1) (i.e. full equation)
Equation would subsume both two marks 2 [4]

12. (i) H2O NH3
2 3 (1)
2 1 (1) 2 (ii) shape (1) bond angle labelled on diagram as 107° (1)

shape (1) bond angle labelled on diagram as 110–120° (1) 4 [6]

13. H bonding from lone pair on O of 1 H2O molecule to H of another (1) dipoles shown (1) Two properties:
Ice is lighter than water/ max density at 4°C (1) explanation: H bonds hold H2O molecules apart / open lattice in ice / H-bonds are longer (1) Higher melting/boiling point than expected (1) explanation: strength of H bonds that need to be broken (1) must imply that intermolecular bonds are broken High surface tension/viscosity (1) explanation: strength of H bonds across surface (1) [6]

14. (a) (atoms of) same element/same atomic number….. with different numbers of neutrons/different masses 1 (b) 3 isotope | percentage composition | number of | | | protons | neutrons | electrons | 85Rb | 71 to 73 | 37 | 48 | 37 | 87Rb | 27 to 29 | 37 | 50 | 37 | mark | must add up to 100 | | | | ie 1 mark for each atomic structure; 1 for  compositions.

= 85.6 2nd mark for significant figures 2 71/29: 85.58 = 85.6 73/27: 85.54 = 85.5 (c) carbon-12/12C 1 [7]

15. atomic radii of Rb  atomic radii of elements above/ Rb has electrons in shell further from nucleus / Rb has more shells Rb has more shielding ( ‘more’ is essential) (increased) nuclear charge is outweighed / despite increased nuclear charge …..by at least one of the factors above/ less attraction/ held less tightly [3]

16. (i) Simplest (whole number) ratio of atoms/moles/elements 1 (ii) ratio Rb : Ag : I = 7.42/85.5 : 37.48/108 : 55.10/127 or 0.0868 : 0.347 : 0.434 or 1 : 4 : 5 = RbAg4I5 2 [3]

17. (i) 1s22s22p63s23p6 1 (ii) 3 1 (iii) 10 1 (iv) ‘dot-and-cross’ of Ca2+ with either 8 electrons or no electrons. ‘dot-and-cross’ of 2OH– correct 2 N.B. H electron and Ca electrons can look the same. [5]

18. (i) attraction between oppositely charges ions 1 (ii) shared pair of electrons 2 ‘shared electrons’ scores 1 mark only [3]

19. (i) attraction of an atom/element for electrons in a (covalent) bond/bonded pair 2 (ii) one element attracts bonded pair more /is more electronegative than other  – on more electronegative atom and  on less 2 electronegative element in example May need to look for these marks below if not given here. [4]

20. H–bond shown between H of one molecule and O, N or F of another H-bond shown going to a lone pair [2]

21. (a) 3 element | structure | bonding | | Mg | giant | metallic |  | Si | giant | covalent |  | S | simple | covalent |  | 1 mark for each correct row (b) Si has strong forces between atoms/ covalent bonds are broken
P has weak forces between molecules/ intermolecular forces/van der Waals’ forces are broken 2 (c) From Na  Al, no of delocalised electrons increases charge on positive ion increases/ ionic size decreases/ charge density increases attraction between  ions and electrons increases/ metallic bonding gets stronger 2 [7]

22. (a) (i) 12  50/1000 = 0.600 mol 1 (ii) 4 mol HCl  1 mol Cl2 / moles Cl2 = 0.15 mol vol of Cl2 = 0.15  24 = 3.60 dm3 2 2nd mark is consequential on molar ratio given (b) Evidence that the oxidation number of Mn has reduced and one of the oxidation numbers correct (ie MnO2: ox no of Mn = 4 or MnCl2: ox no of Mn = 2
The other oxidation number of Mn is correct, ie in MnO2: ox no of Mn = 4 or in MnCl2: ox no of Mn = 2 2 [5]

23. (i) 2Na(s)  Cl2(g)  2NaCl(s) 1st mark for equation 2 2nd mark for state symbols (ii) Giant ionic (lattice) or 3D with alternating Na and Cl– 2 [4]

24. With Br–, goes yellow/orange/red ‘precipitate’ makes this incorrect. With I–, goes purple/brown/brown ‘precipitate’ should be ignored Cl2  2Br–  Br2  2Cl– Cl2  2I–  I2  2Cl– Or full equations using soluble halides, eg NaBr If both equations given with correct species but not balanced, award 1 mark reactivity trend: Cl more reactive than both Br and I/ Cl is the most reactive Cl (atoms) are smaller (ora) / attraction for electrons or electron affinity is greater / 6 Cl is a stronger oxidising agent ignore any reference to ‘electronegativity’. QoWC: At least 2 sentences in which the meaning is clear. 1 [7]

25. (a) 2 1, 2 or 3 p orbitals are OK (b) d orbital 2 p sub-shell 6 3rd shell 18 3

(i) (ii) 2 2s and 2p labels Ignore any superscripted numbers. 8 electrons in correct levels with arrows correctly shown [7]

26. (i) Energy change when each atom in 1 mole of gaseous atoms loses an electron (to form 1 mole of gaseous 1 ions). 3 (ii) O2+(g)  O3+(g)  e− 2 1 mark for correct species; 1 mark for state symbols No charge required on electron. Ignore (g) on e (iii) Large difference between 6th and 7th IEs 2 marking a different shell (closer to nucleus) allow ‘inner shells’/new shell/full shell/first shell marking points independent. not sub-shell or orbital [7]

27. (i) mass = 0.0500  23.0 = 1.15 g 1 (ii) moles H2 = 0.0250 volume H2 = 0.0250  24 = 0.600 dm3 2 ecf from calculated moles H2 0.0500 mol in 50.0 cm3 1 (iii) concentration = 0.0500  20 = 1.00 mol dm−3 [4]

28. Also accept Na with full shell as long as it contains ‘x’s (as in example above) Ignore any inner shells correct dot and cross correct charges [2]

29. (i) 2Na  O2  Na2O2 1 (ii) Na2O2  2H2O  H2O2  2NaOH 1 correct covalent bonds shown (iii) electron count (14) for rest of molecule correct 2 [4]

30. (a) add AgNO3 /add Ag+ 3 ignore ammonia white (precipitate)/goes white/precipitate that dissolves in dilute NH3(aq) Ag+  Cl−  AgCl (ignore state symbols) (b) add NaOH 2 Cl2  2NaOH  NaCl  NaClO  H2O or partial or completely ionic equation: Cl2  2NaOH  2Na+  ClO–  Cl–  H2O/ Cl2  2OH–  ClO–  Cl–  H2O [5]

31. number of electrons /electron shells increases down group van der Waals’ forces /induced dipoledipole interactions forces greater Cl2 < Br2 < I2 [3]

32. (i) (trigonal) pyramidal 1 (ii) electron pairs repel/bonds repel /electron pairs get as far apart as possible lone pairs repel more/forces ‘them’ closer 4 electron pairs surround central atom or N 3 /diagram with 3 bonds and a lone pair [4]

33. (i) They have different numbers of protons/ Ba has one more proton/Ba has 56 p+; Cs has 55 p+ 1 (ignore electrons: any mention of ‘neutrons’ is wrong) (ii) s 1 (iii) Cs to Ba: nuclear charge increases/more protons electrons are in: the same shell/sub-shell/orbital /similar shielding/same shielding 3 attraction increases/pull increases …….ORA (iv) smaller 2 shell has been lost/less shielding/less electron repulsion/proton : electron ratio larger mark separately [7]

34. (i) loss (of electrons) 1 (ii) Ba 0  ()2 (accept 2) 2 [3]

35. Original solution contains ions/there are mobile ions Charge carriers removed as reaction takes place /as solid forms/ as BaSO4 forms/as water forms 2 [2]

36. M(BaO) = 137  16 = 153 moles BaO = 500/153 or 3.268 mol moles Ba = 3.268/2 or 1.634 mass Ba formed = 1.634  137 = 224 g accept 223.856209/223.86/223.9 g. if 6 mol BaO forms 3 mol Ba, award 3rd mark Alternative method mass 6BaO=918 g mass 3Ba = 411 g 1g BaO forms 411/918 g Ba 500 g BaO forms 223.856209/223.86/223.9 g Ba [4]

37. general NaCl: ionic/has ionic bonds Beware of contradictions for this mark, especially reference to intermolecular forces. Ignore ‘atoms’. 2 graphite: covalent/giant molecular/macromolecular Ignore van der Waals’, intermolecular, molecules -------------------------------------------

conductivity NaCl: ions cannot move/ no free ions (or electrons) / mobile ions only in solution or when molten graphite: 2 delocalised electrons/ free electrons (between layers)/ electrons conduct Ignore lone pair melting point both graphite and NaCl: bonds are strong/ bonds difficult to break / 1 large amount of energy is needed to break bonds solubility NaCl: Water is polar/water has a dipole/ ions interacts with water molecules Graphite: no interaction with water/ no intermolecular forces with water/ 2 graphite is non-polar QWC: At least 2 complete sentences in which the meaning is clear. 1 [8]

38. (i)

protons neutrons electrons 25Mg 12 13 12
26Mg 12 14 12 2 (ii) 1s22s22p63s2 24  78.60/100  25  10.11/100  26  11.29/100 1 (iii) = 24.33 (calc value: 24.3269. This scores one mark)
24.32 with no working, award 1 mark only.
24.3 with no working, no marks (Periodic Table value) 2 [5]

39. (i) positive ions electrons (must be labelled)
If Mg2+ shown then must be correct: Mg+ not worthy 2 (ii) electrons move 1 [3]

40. (i) Oxidation state goes from 0 in O2
 2 in MgO 2 (ii) or with Mg full shell. correct dot and cross; correct charges 2 [4]

41. (i) MgO has reacted with CO2 1 (ii) Solid dissolves / disappears
Fizzing / bubbles 2
MgO  2HCl  MgCl2  H2O
MgCO3  2HCl  MgCl2  CO2  H2O both reactions form magnesium chloride/MgCl2 3 [6]

42. (i) mark vertically: H2O NH3 2 3 2 1 2 3D Diagram required or diagram with name (ii) labelled bond angle required NH3 pyramidal molecule shown 107  (106-108) SO2 non-linear molecule shown 110 – 130  4 [6]

43. (i) oxygen/ nitrogen is more electronegative/ molecule has atoms with different electronegativities
/oxygen/more electronegative atom … attracts bonded electron pair more 1 (ii) H bonding from N of 1 NH3 molecule to H of another NH3 molecule with a Hδ+ shown and a Nδ– shown with lone pair involved in bond 2nd mark is available from water molecule(s) 2 [3]

44. ice is less dense than water hydrogen bonds hold H2O molecules apart in ice / hydrogen bonds cause an open lattice structure 2 [2]

45. (i) ratio N : H : S : O = : : : : = 2 : 8 : 1 : 3 Empirical formula = N2H8SO3 N2H4SO3 is worth 1 mark from consistent use of at nos. 2 (ii) H2O  2NH3  SO2  (NH4)2SO3 1 (Award mark for N2H8SO3) [3]

46. (i) goes yellow/orange/brown 1 (ii) Cl2  2Br–  Br2  2Cl– OR Cl2  2KBr  Br2  2KCl 1 mark for species. 1 mark for balancing 2 (iii) An electron is being gained Cl atoms are smaller/less shells (ora) In Cl, attraction for electrons is greater 3 [6]

47. (a) (i) Amount of substance that has the same number of particles as there are atoms in 12 g of 12C/ 6  1023/ Avogadro’s Number 1 (ii) moles = = 0.0330 mol moles Cl2 = = 0.0165 mol 1 (iii) volume Cl2 = 0.0165  24000 = 396 cm3 / 0.396 dm3 792 cm3 worth 1 mark (no molar ratio) 1584 cm3 worth 1 mark (x 2) units needed. 2 (iv) bleach / disinfectant /sterilising /killing germs 1 (b) NaClO3 1 [6]

48. (a) Energy change when each atom in 1 mole of gaseous atoms loses an electron (to form 1 mole of gaseous 1 ions). 3 (b) From Li  N, ionisation energy increases number of protons/nuclear charge increases nuclear attraction increases / shell drawn in by increased nuclear charge/ atomic radius decreases across period, electrons added to same shell Not same subshell From Be  B, ionisation energy decreases for B, electron is removed from a p sub-shell/p orbital/different sub-shell which has a higher energy 7 watch for distinction between nuclear attraction and nuclear charge in candidates’ scripts. Also watch for confusion between shell and subshell. Al Sharp rise in successive ionisation energy between 3rd and 4th IE marking a change to a new or different shell / there are 3 electrons in the outer shell 3 mention of ‘orbital’ or ‘sub-shell cancels ‘shell mark’ Each marking point for Al is independent QoWC: links together two pieces of information correctly within two of the sections below: 1. General trend across period 2. Be to B Successive ionisation energies [13]

49. (i) CaCO3 (s)  2HCl(aq)  CaCl2(aq)  CO2(g) H2O (l) CaO(s)  2HCl(aq)  CaCl2(aq)  H2O (l) each balanced equation 1 mark (2) all state symbols (1) 3 (ii) CaCO3 fizzes/ gas given off/ gas evolved / carbon dioxide evolved (1) 1 [4]

50. (i) (atoms of) same element/same atomic number/number of protons with different numbers of neutrons/diff masses 1 (ii) proton neutron electron relative mass 1 1 / negligible relative charge 1 0 −1 i.e. 1 mark for each correct row for electron, accept 1/1500 – 1/2000 for charges, accept ; 0; – 2 [3]

51. (i) average atomic mass/weighted mean/average mass compared with carbon-12 1/12th of mass of carbon-12/on a scale where carbon-12 is 12 OR (ii) The mass of 1 mole of atoms of an element compared with 12 g of carbon-12 3 Ar = / 121.8558 = 121.9 2 [5]

52. (i) 107 (accept any angle in the range 108  91) 1 (ii) electron pairs repel electron pairs/bonds go as far apart as possible lone pairs repel more 2 [3]

53. (i) Mass Sb2S3 in stibnite = 5% of 500 kg = 25.0 kg Moles Sb2S3 = / 73.5/ 73.529 /73.53/ 74 mol (calculator value: 73.52941176) If 5% is not used, 1471 mol; ecf for 2nd mark (calculator value: 1470.588235) If 5% is used 2nd, 73.6 mol: OK for both marks 2 (ii) moles Sb = 2  73.5 mol mass Sb = 2  73.5  122 g = 17.9 kg If the 2 isn’t used, answer = 73.5  122 = 8.95 ecf ans from (i) x 2 ecf ans above x 2 OR % Sb = 244/340 = 71.7% mass Sb = 25.0  71.7/100 = 17.9 kg (ecf as above) 2 [4]

54. (i) hydrogen / H2 1 (ii) Sr  2H2O  Sr(OH)2  H2 1 (iii) different numbers of moles/atoms/ different Ar values so different number of moles of H2 /more moles of Ca (i.e. an attempt to quantify difference) 2 (iv) 8 – 14 1 [5]

55. (i) Ca+(g)  Ca2+(g)  e− Equation with correct charges and 1 electron lost state symbols ‘−’ not required on ‘e’ 2 (ii) same number of protons or same nuclear charge attracting less electrons/ electron removed from an ion/ less electron-electron repulsion (not less shielding)/ ion is smaller 1 (iii) atomic radii of Sr > atomic radii of Ca/ Sr has electrons in shell further from nucleus than Ca/ Sr has electrons in a higher energy level/ Sr has more shells Therefore less attraction Sr has more shielding than Ca (‘more’ is essential) 3 increased nuclear charge is outweighed / despite increased nuclear charge …..by at least one of the factors above [6]

56. attraction between oppositely charged ions/ oppositely charged atoms 1 For CaO: correct dot and cross ; correct charges For CO2: correct dot and cross 3 1s22s22p63s23p6 1 [5]

57. (i) Molar mass CaO = 56.1 (g mol–1) (anywhere) 2 moles CaO = = = 0.0267/0.027 calc: 0.0267379 Allow 56 which gives 0.0268 (ii) moles HNO3 = 2  0.0267 = 0.0534 or 0.0535 /0.053 mol (i.e. answer to (i) x 2) volume of HNO3 = = 21.4 cm3 2 calc from value above = 21.3903743 If 0.053 mol, answer is 21 cm3 but accept 21.2 cm3 If 0.054 mol, answer is 22 cm3 but accept 21.6 cm3 [4]

58. (i) dative covalent, bonded pair comes from same atom/ 1 electron pair is donated from one atom/ both electrons are from the same atom (ii) Ca(NO3)2  CaO  2NO2  ½O2 or double equation with 2/2/4/1 1 [2]

59. (i) 203.3 g mol−1 1 Accept 203 (ii) white precipitate / goes white 1 (iii) Ag+(aq)  Cl−(aq)  AgCl(s) equation state symbols 2 AgCl dissolves in NH3(aq) (iv) AgBr dissolves in conc NH3(aq)/ partially soluble in NH3(aq) AgI insoluble in NH3(aq) 3 [7]

60. Cl2: 0 HOCl 1 HCl −1 [4]

61. High boiling point or difficult to break linked to strong bonds in the right context within Li or C 1 Li conducts by delocalised/free/mobile electrons structure: giant metallic 3 or ‘ ions with a sea of electrons’ for giant mark C conducts by delocalised/free/mobile electrons structure: giant covalent with layers 4 N No mobile charge carriers/electrons/ions to conduct electricity simple molecular structure/made of N2 molecules low boiling point or easily broken due to 3 intermolecular forces/ van der Waals’ forces QWC: At least 2 complete sentences in which the meaning is clear. 1 [12]

62. (i) a proton donor 1 (ii) MgO  2HCl  MgCl2  H2O 1 [2]

63. isotope | protons | neutrons | electrons | 12C | 6 | 6 | 6 | | 13C | 6 | 7 | 6 | | [2]

64. (i) mass spectrometry 1 (ii) mass of an isotope compared with carbon-12 1/12th of mass of carbon-12/on a scale where carbon-12 is 12 2 mass of 1 mole of the isotope/mass of 1 mole of carbon-12 is equivalent to the first mark “mass of the isotope that contains the same number of atoms as are in 1 mole of carbon-12”  1 mark (mark lost because of mass units) (iii) 12  95/100  13  5/100 OR 12.05
= 12.1 (mark for significant figures)
(12.1 scores both marks) 2 [5]

65. 1s22s22p2 [1]

66. CO2: correct covalent bonds around carbon outer shell electrons correct (must be ‘dot AND cross’ or electron source clearly shown (different coloured for source?) [2]

67. CaCO3  CaO  CO2 state symbols not required [1]

68. (i) moles CO2 = 1000 /44 mol = 22.7 mol volume CO2 in 2000 = 22.7  24 = 545 dm3 (ii) reduction = 545  60/100 = 327 dm3 [3]

69. (a) ……Ca(s)  …..2 HCl(aq) …….CaCl2(aq)  .H2(g). 2 (g) not required for H2

(b) In Ca, oxidation state = 0 and 2
In CaCl2, oxidation state = 2
Oxidation number increases from Ca to CaCl2 [4]

70. correct dot and crosses correct charges [2]

71. (i) white precipitate/goes white 1 (ii) Ag  Cl–  AgCl 1 state symbols not required [2]

72. (i) moles HCl = 2.0  50/1000 = 0.10 1 (ii) moles Ca = ½  moles HCl = 0.050 mass Ca = 40.1  0.050 = 2.00 g / 2.005 g 2 (accept 40  0.050 = 2.0 g) (mass Ca of 4.0 g would score 1 mark as ‘ecf’ as molar ratio has not been identified) (iii) Ca has reacted with water
Ca  2H2O  Ca(OH)2  H2 state symbols not required 1st mark for H2 3 2nd mark is for the rest of the balanced equation [6]

73. (i) O 1 (ii) AI 1 (iii) P 1 (iv) C/Si 1 (v) N/P 1 (vi) Mg 1 (vii) Na 1 (viii) Si 1 [8]

74. removed for test 75. uneven distribution of electrons instantaneous /oscillating/changing/temporary/transient/ dipole on one atom causes an induced/resultant dipole on another molecule/atom chlorine gas; bromine liquid; iodine solid/ volatility decreases from Cl2  Br2  I2/ boiling point increases from Cl2  Br2  I2/ stronger forces are broken from Cl2  Br2  I2 number of electrons increases down group greater/more van der Waals’ forces / induced dipole- dipole interactions / forces between the molecules [6]

76. Reactivity decreases down group/ Cl2  Br2  I2 / Cl2 displaces Br2 AND Br2 displaces I2 chlorine: Cl2  bromide  yellow ………/ orange ………. bromine: Br2  iodide  darker orange/brown or purple in organic solvent Cl2  2Br−  Br2  2Cl− Br2  2I−  I2  2Br− (or full equations) Cl2 is stronger oxidising agent than Br2 AND Br2 is stronger oxidising agent than I2 / 5 Cl2 has greater attraction for electrons than Br2 AND Br2 has greater attraction for electrons than I2 QoWC: At least two sentences that show legible text with accurate spelling, punctuation and grammar so that the meaning is clear. 1 (Mark this from anywhere within Q4) [6]

77. (a) (i) atoms of same element/same atomic number….. with different numbers of neutrons/different masses 1 (ii) isotope protons neutrons electrons 2 46Ti 22 24 22 47Ti 22 25 22 (b) = 47.7 2 [5]

78. 1s22s22p63s23p63d24s2 [1]

79. (i) positive ions electrons (must be labelled) 2 (ii) electrons move 1 [3]

80. (i) moles Ti  1.44/47.9  0.0301 mol/0.03 mol 1 (accept use of answer from (b)) (ii) mass of Cl  5.70-1.44  4.26 g moles Cl  4.26/35.5  0.120 mol 2 5.70/35.5  0.161 mol gets 1 mark (iii) Ti:Cl  0.0301 : 0.12  1:4. Empirical formula  TiCl4 0.0301 : 0.161 mol gives TiCl5 for 1 mark 1 (iv) Ti  2Cl2  TiCl4 1 (ecf possible from (iii) covalent [5]

81. simple molecular 2 [2]

82. (a) RaCl2 1 (b) Reduction is gain of electrons/decrease in oxidation number Ra2+ gains 2 electrons  Ra/ Oxidation state goes from 2 in RaCl2  0 in Ra 2 [3]

83. (i) effervescence/bubbles Ra disappears/dissolves 2 (ii) 8-14 1 [3]

84. (i) First ionisation (energy) 2 Ra(g)  Ra+(g)  e− 1 mark for equation 1 mark for state symbols ‘‘ not required on ‘e’ 2 (ii) atomic radii of Ra > atomic radii of Ca/ Ra has electrons in shell further from nucleus than Ca/ Ra has more shells Ra has more shielding than Ca : ‘more’ is essential Ra electron held less tightly/less attraction on electron 3 [7]

85. (a) …Mg(OH)2(s)  2…HCl(aq)  ….MgCl2(aq)  2…H2O(l) 1 (b) (i) moles HCl  0.108  500/1000  0.054 1 (ii) moles Mg(OH)2  ½  moles HCl  0.027 molar mass of Mg(OH)2  24.3  17 × 2  58.3 (do not penalise 24) mass Mg(OH)2 = 58.3  0.027 = 1.57 g / 1.5741 g (accept ans from (ii)  0.027 = 1.566 g) (mass Mg(OH)2 of 3.15 g would score 2 marks as ‘ecf’ as 3 molar ratio has not been identified) (iii) Too much if 2.42 g (dose)  ans to (ii) (If answer to (ii)  2.42 g then ‘correct’ response here would 1 be ‘Not enough’ [6]

86. CaCO3 reacts with (or neutralises) HCl (or CaCO3  HCl in an equation) CaCO3  2HCl  CaCl2  H2O  CO2 (correct equation would score both marks) [2]

87. removed for test 88. (i) Cl2  2I−  I2  2Cl− 2 1 mark for species. 1 mark for balancing (ii) Cl atom is smaller/has less shells electron to be captured will be attracted more 2 [4]

89. (i) H bonding from O of 1 H2O molecule to H of another dipoles shown with lone pair involved in bond 3 (ii) Two properties from: Ice is lighter than water/ max density at 4C explanation: H bonds hold H2O molecules apart / open lattice in ice / H-bonds are longer Higher melting/boiling point than expected explanation: strength of H bonds that need to be broken must imply that intermolecular bonds are broken High surface tension/viscosity explanation strength of H bonds across surface 4 [7]

90. NH3: 107 (range 106  108) electron pairs repel other electron pairs lone pair has more repulsion electron pairs get as far apart as possible [4]

91. N has less protons than O (ora) electrons are in same shell /have same or similar shielding weaker nuclear attraction in N (ora) shell drawn in less by nuclear charge in N (ora) watch for distinction between nuclear attraction and nuclear charge in candidates’ scripts. QoWC: links together two statements in at least two of the sections (a)(ii), (b) and (c) [4]

92. (i) as a base (1) ………. accepts a proton/H/ neutralises an acid/ reacts with acid to form salt/ has a lone pair of electrons (1) 2 (ii) fertiliser (1) 1 (iii) manufacture of explosives/ dyes/ nitric acid/ fibres/ ammonium nitrate/ urea/ refrigeration/ cleaning agents/ fertiliser
(if not allowed in (ii) (1) 1 [4]

93. (i) 79Br has two less neutrons than 81Br 2 (ii) 79Br have same numbers of protons and same number of electrons 2 [4]

94. (i) 1s22s22p63s23p6..........3d104s24p5 2 Award 1 mark for p5. (ii) Highest energy sub-shell/sub-shell/being filled is the p sub-shell/outer electrons are in a p (sub-shell/orbital/shell) 1 [3]

95. (i) Number AND type of atoms (making up a 1 molecule)/number of atoms of each element Not ratio (ii) P4  6 Br2  4 PBr3 1 (iii) ratio P : Br = 16.2/31 : 83.8/79.9 /= 0.52 : 1.05 /= 1 : 2 Empirical formula = PBr2 Correct compound = P2Br4 /phosphorus(II) bromide but 3 not PBr2 [5]

96. shared pair of electrons i.e. ‘shared electrons’ is worth 1 mark. pair of electrons for second mark [2]

97. H2O: all correct including lone pairs around O CO2: correct covalent bonds around carbon lone pairs added around oxygen atoms (must be ‘dot AND cross’ or electron source clearly shown (different coloured for source is OK) [3]

98. (i) molecule shown as non-linear angle: 104 - 105 molecule shown as linear 4 (ii) angle: 180 shape of H2O shape of CO2 Electron pairs repel/groups (or regions) of electrons 2 repel/electron pairs get as far apart as possible Oxygen in water surrounded by 4 areas of electron density/2 bonds and 2 lone pairs AND Carbon in CO2 surrounded by 2 regions of electron density/2 double bonds [6]

99. (i) Attraction of electrons in a bond towards an atom 2 (ii) CO2 is symmetrical/H2O is not symmetrical In CO2, dipoles cancel/in H2O, the dipoles don’t cancel 2 [4]

100. (a) Energy change when each atom in 1 mole of gaseous atoms 3 loses an electron (to form 1 mole of gaseous 1 ions). (b) increasing nuclear charge/number of protons electrons experience greater attraction or pull/atomic radius decreases/electrons added to same shell/same or similar shielding 2 [5]

101. (From 2 10 18 / down group) 1st ionisation energies decrease/easier to remove electrons electron is further from nucleus/ atomic radius increases/ electron in a different shell/ atoms increase in size (not sub-shell or orbital) electron experiences more shielding (more is essential here) distance and shielding outweigh the increased nuclear charge NOT: attraction/pull; effective nuclear charge [4]

102. Strontium reacts with oxygen/strontium oxide forms/SrO forms 2Sr  O2  2SrO / Sr  ½ O2  SrO [2]

103. (i) In Sr, oxidation number = 0 In Sr(OH)2, oxidation number = ()2 OR Oxidation number increases from Sr  Sr(OH)2 by 2 2 (ii) 0.438/87.6 = 5.00  10−3 / 0.00500 mol 1 (iii) 0.00500  24.0 = 0.120 dm3 (accept 120 cm3) 1 (iv) 0.00500  1000/200 = 0.0250 mol dm−3 1 [5]

104. (i) heat 1 (ii) ...3..SrO(s)  ...2..Al(s)  ...3..Sr(s)  ....Al2O3(s) 1 (iii) Molar mass of SrCO3 = 87.6  12  16x3 = 147.6 g mol−1 Mass SrCO3 required = 100  147.6/87.6 = 168 tonnes Mass of ore needed = mass SrCO3  100/2 = 168  100/2 = 8400 tonnes / 8425 tonnes (from 168.484931507) (answer depends on rounding) 5000 tonnes is 50  100 tonnes: worth 1 mark 3 (iv) 98% waste produced which must be disposing of /made into something worthwhile/CO2 being removed by something sensible/ 1 any sensible comment [6]

105. removed for test 106. (i) fizzing/gas/hydrogen evolved or Mg dissolves/disappears 1 [an incorrect observation negates this mark] (ii) 2HCl  Mg  MgCl2  H2 [correct formula for MgCl2. Allow equation with HI/MgI2 instead of HCl] [balancing: e.g. 2HCl  2Mg  2MgCl  H2 will get this mark but not the 1st] 2 [3]

107. isotope protons neutrons electrons nickel-58 28 30 28 nickel-60 28 32 28 nickel-62 28 34 28 For ecf, 3rd column same as first column. [3]

108. (i) mass spectrometry mass spec… /mass spectrometer should also be credited 1 (ii) average mass/weighted mean mass of an atom compared with carbon-12 1/12th of mass of carbon-12/on a scale where carbon-12 is 12 mass of 1 mole of atoms (of an element) mass of 1 mole of 3 carbon-12 is equivalent to first two marks “mass of the element that contains the same number of atoms as are in 1 mole of carbon-12”  2 marks (mark lost because of mass units) (iii) 63.0  77.2/100  65.0  22.8/100 / 63.456 2 = 63.5 (mark for significant figures) (iv) copper/ Cu 1 [7]

109. (i) mass of Ni = 2.0g moles of Ni = 2.0/58.7 mol = 0.0341/0.034 mol (1 mark would typically result from no use of 25%  0.136 mol) 2 2nd mark is for the mass of Ni divided by 58.7 (ii) number of atoms of Ni = 6.02  1023  0.0341 1 = 2.05  1022 / 2.1  1022 atoms Can be rounded down to 2.1 or 2.0 or 2 (if 2.0) From 8 g, ans = 8.18/8.2  1022 (and other consequential responses) [3]

110. (i) positive ions/cations and negative electrons Can be described in words only for both marks 2 (ii) contain free/mobile/delocalised electrons 1 [3]

111. (i) shared pair of electrons 2 i.e. ‘shared electrons’ is worth 1 mark. Pair of electrons for second mark (ii) correct dot-and cross diagram 1 [3]

112. (i) electrostatic attraction between oppositely charged ions 2 (charged or electrostatic for 1st mark) (ii) correct dot-and cross diagram correct charges 2 (iii) Mg  Mg2+  2e− F2  2e−  2F− 2 –sign not required with electron (iv) solid: ions cannot move /in fixed positions in lattice solution: ions are free to move 2 [8]

113. (a) NaClO, oxidation state = 1 NaCl, oxidation state = −1 OR 2 Oxidation number decreases from NaClO  NaCl by 2 (b) (i) 84/24000 = 3. 5  10−3 mol 1 (ii) 3.5  10−3 mol 1 ans to (i) (iii) 3.5  10−3  1000/5 = 0.70 mol dm−3 1 ans to (ii) x 1000/5 (c) molar mass of NaClO = 23  16  35.5 = 74.5 (g mol−1) concentration = 0.70  74.5 = 52.15 g (dm−3) ans to (iii) x 74.5 bleach is 5.215 g per 100 cm3 and the information is correct (as this value exceeds 4.5%) 3 response depends upon answer to (b)(iii). Could be opposite argument if ans < 4.5% OR molar mass of NaClO = 23  16  35.5 = 74.5 (g mol−1) moles of NaOCl = 4.5/74.5 = 0.0604 mol (in 100 cm3) bleach is 10  0.0604 = 0.604 mol dm−3 which is less than answer to (b)(iii) and therefore label is correct. response depends upon answer to (b)(iii). Could be opposite argument if ans 0.604 (d) 2HCl  NaClO  Cl2  NaCl  H2O 2 Award one mark for: HCl  NaClO  Cl2  NaOH [10]

114. (i) Answer is inclusive of 9  14 inclusive 1 (ii) Ca(s): 1s22s22p63s23p64s2 Ca(OH)2(aq): 1s22s22p63s23p6 2 [3]

115. removed for test

116. H2O H bonding from O of 1 molecule to H of another dipoles shown or described 3 with lone pair of O involved in the bond CH4 van der Waals’ forces from oscillating dipoles/ temporary dipoles/ transient dipoles/ instantaneous dipoles leading to induced dipoles caused by uneven distribution of electrons 3 [6]

117. Two properties from: Ice is less dense/lighter than water/floats on water/ max density at 4C explanation: H bonds hold H2O molecules apart / open lattice in ice / H-bonds are longer 2 Higher melting/boiling point than expected Not just high Accept: ‘unusually high/strangely high/relatively high’ explanation: H bonds need to be broken 2 must imply that intermolecular bonds are broken High surface tension explanation strength of H bonds across surface mark 2 properties only  4 max QoWC over whole question 1  legible text with accurate spelling, punctuation and grammar [5]

118. No mark scheme available

119. No mark scheme available