Mark Scheme November 2007

Transcription

1 Mark Scheme November 2007 IGCSE IGCSE Chemistry (4335) Edexcel Limited. Registered in England and Wales No Registered Office: One90 High Holborn, London WC1V 7BH

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3 Contents 1. Paper 1F 4 2. Paper 2H Paper

4 CHEMISTRY 4335, November 2007, MARK SCHEME Key / indicates alternatives eq allow for correct equivalent word underlined means no alternatives allowed Paper 1F 1 (a) 8 1 (b) 6 1 (c) Si 1 (d) N 4

5 1 (e) 6 Total 5 marks 2 (a) Protons / electrons 2 (b) Neutrons 2 (c) Elements 2 (d) Compounds 5

6 2 (e) Electrons 2 (f) Carbon Total 6 marks 3 (a) Distillation Fractional distillation 3 (b) Crystallisation / evaporation 3 (c) Filtration/ decantation 6

7 3 (d) Chromatography 3 (e) Fractional distillation Distillation Total 5 marks 4 (a) s l aq g 4 correct = 2, 3/2 correct = 1 and 1/0 correct = 0. (2) 4 (b) Fizzing/effervescence/bubbles Moves/darts about Reference to flames. Gets smaller /Disappears Floats Reject dissolves Max 2. (2) 7

8 4 (c) Lithium Li 4 (d) (add) red litmus/universal indicator turns blue. Allow purple for UI (2) Total 7 marks 5 (a) brown / red-brown/ orange-brown/ foxy brown Rusty Orange Red 5 (b) air / oxygen water/ moisture/ dampness (2) 5 (c) iron (III) oxide accept iron oxide Ignore reference to hydrated 8

9 5 (d) oxidation (3 rd box) 5 (e) Galvanising 5 (f) (cover with) oil / grease / paint / plastic Total 7 marks 6 (a) hydrochloric acid hydrogen chloride 6 (b) effervescence / fizzing / bubbles / solid disappears or dissolves 9

10 6 (c) limewater cloudy / milky / white precipitate (2) 6 (d) other gases are acidic other gases give some result 6 (e) sulphur dioxide + water sulphurous acid accept sulphuric (IV) acid 6 (f) fish harmed/killed stonework eaten away/ OWTTE iron rusts (more quickly) plants killed Max 2 (2) Total 8 marks 10

11 7 (a) H H H C C H H H Ignore bond angles 7 (b) C 3 H 8 7 (c) C n H 2n+2 (2 nd option) 7 (d) similar chemical properties Bottom box 7 (e) contain only carbon and hydrogen 11

12 7 (f) butane + oxygen carbon dioxide + water (reactants = 1, products = 1) (2) Total 7 marks 8 (a) (i) iron oxide (III) accept iron oxcide/ haematite / Fe 2 O 3 iron ore (ii) coke / carbon / C (not coal) (iii) limestone / calcium carbonate / CaCO 3 lime marks (i) (iii) can be awarded in any order (iv) slag / calcium silicate / CaSiO 3 (v) iron / Fe award 1 if (iv) and (v) are correct but in wrong order Iron (II) or iron (III) 8 (b) (i) 1 (ii) carbon dioxide loses oxygen/ oxidation number of carbon decreases 12

13 8 (c) toxic / poisonous/ correct effect on blood 8 (d) too reactive / higher than carbon in reactivity series/ very reactive Total 10 marks 9 (a) (i) C / F (ii) A and B (iii) E 13

14 9 (b) Poly(()ethene()). Accept polythene/polyethylene correct repeat unit H Or any multiple length C (2 + carbons) H continuation bonds first mark awarded) or.... (only if Ignore brackets and n or other subscripts Total 6 marks 10 (a) 0 for mass Particle Relative mass Relative charge Electron Neutron 0 / nil Proton 1 (4) Ignore negligible 10 (b) (i) helium /carbon / nitrogen / oxygen / neon / magnesium / silicon / sulphur / calcium (ii) silicon (iii) hydrogen Max penalty 1 if give symbols for all 3 rather than names 14

15 10 (c) 7 10 (d) (i) full / complete ignore saturated (ii) unreactive/inert/do not undergo reactions Total 10 marks 11 (a) zinc is less reactive than magnesium Magnesium is more reactive than Zinc It is more reactive Or correct reference to positions in reactivity series 11 (b) (i) Fe + CuSO 4 FeSO 4 + Cu reagents products incorrect balancing = -1 be generous with cases (ii) (dark) grey to pink-brown blue to green (2) (2) Ignore additional information 15

16 11 (c) hydrogen more reactive than copper hydrogen less reactive than iron Iron(II) or Copper (II) Hydrogen between Fe + Cu for both marks Total 9 marks 12 (a) (i) enthalpy / (heat) energy change (ii) increases/goes up Mark independently. Ignore reference to bonds. 12 (b) Water Formulae 16

17 12 (c) stir (allow heat) excess magnesium carbonate filter evaporate/heat/window-ledge crystallisation point Cool final separation (decant/filter/tweezers) Suitable method of drying. Allow use of oven but not if T > 100 c; filer paper mark dependant on crystals being separated. If heated to dryers then no further marks given (evaporating stage) If excess acid, max 3 Max 5 (5) Total 9 marks 13 (a) (i) shared electron pair all other electrons correct (ignore inner shells even if wrong) (ii) bottom box crossed 17

18 13 (b) (i)h + /H 3 O + other ions negate (ii) no acid made / no Hydrogen ions stays covalent/does not ionize 13 (c) (i) red/ orange bleached/ white (ii) same number of electrons / same electronic configurations Same protons negates 13 (d) add sodium hydroxide (solution)/ammonia solution/ ammonium hydroxide green ppt/solid/suspension Orange/brown/orange-brown/foxy brown/rusty brown/red-brown ppt/ solid/suspension If miss out ppt then give 1 mark for 2 correct colours result marks only given if test correct Powder/crys tals/bits Orange/ rusty/red Total 11 marks Paper total 100 marks 18

19 Paper 2H 1 (a) (i) C / F (ii) A and B (iii) E 1 (b) Poly(()ethene()). Accept polythene/polyethylene correct repeat unit H Or any multiple length C (2 + carbons) H continuation bonds mark awarded) or.... (only if first Ignore brackets and n or other subscripts Total 6 marks 2 (a) Particle Relative mass Relative charge Electron Neutron 0 / nil Proton 1 (4) Ignore negligible 19

20 2 (b) (i) helium /carbon / nitrogen / oxygen / neon / magnesium / silicon / sulphur / calcium (ii) silicon (iii) hydrogen Max penalty 1 if give symbols for all 3 rather than names 2 (c) 7 2 (d) (i) full / complete ignore saturated (ii) unreactive/inert/do not undergo reactions Total 10 marks 3 (a) zinc is less reactive than magnesium Magnesium is more reactive than Zinc Or correct reference to positions in reactivity series It is more reactive 20

21 3 (b) (i) Fe + CuSO 4 FeSO 4 + Cu reagents products incorrect balancing = -1 be generous with cases (ii) (dark) grey to pink-brown blue to green (2) (2) Ignore additional information 3 (c) hydrogen more reactive than copper hydrogen less reactive than iron Iron(II) or Copper (II) Hydrogen between Fe + Cu for both marks Total 9 marks 4 (a) (i) enthalpy / (heat) energy change (ii) increases/goes up Mark independently. Ignore reference to bonds. 4 (b) Water Formulae 21

22 4 (c) stir (allow heat) excess magnesium carbonate filter evaporate/heat/window-ledge crystallisation point Cool final separation (decant/filter/tweezers) Suitable method of drying. Allow use of oven but not if T > 100 c; filer paper mark dependant on crystals being separated. If heated to dryers then no further marks given (evaporating stage) If excess acid, max 3 Max 5 (5) Total 9 marks 5 (a) (i) shared electron pair all other electrons correct (ignore inner shells even if wrong) (ii) bottom box crossed 5 (b) (i)h + /H 3 O + other ions negate (ii) no acid made / no Hydrogen ions stays covalent/does not ionize 22

23 5 (c) (i) red/ orange bleached/ white (ii) same number of electrons / same electronic configurations Same protons negates 5 (d) add sodium hydroxide (solution)/ammonia solution/ ammonium hydroxide green ppt/solid/suspension Orange/brown/orange-brown/foxy brown/rusty brown/red-brown ppt/ solid/suspension If miss out ppt then give 1 mark for 2 correct colours result marks only given if test correct Powder/cry stals/bits Orange/ rusty/red Total 11 marks 6 (a) (i) sugar / carbohydrate (ii) CH 2 O Ignore glucose 6 (b) solution / dissolve in water yeast = C no air / oxygen Any other condition = 1 Max 2 (2) 23

24 6 (c) (i) C 2 H 4 + H 2 O C 2 H 5 OH (ii) phosphoric acid steam / heat / high temperature / temperature range C high pressure / pressure range atm (2) (ii) max 2 6 (d) shortage/cost of (crude) oil/ petroleum availability of sugar (cane) Petrol glucose 6 (e) (i) sodium/ Na (ii) sodium ethoxide (iii) ionic Total 12 marks 7 (a) (i) S 8 (ii) (I) covalent (bonding)/bonds between atoms (II) van der Waals'/intermolecular forces/bonds between molecules 24

25 7 (b) (i) 2SO 2 + O 2 2SO 3 ACCEPT all formulae correct balancing (ii) 450 C / temperature in range C 1-2 atm (accept atmospheric pressure) vanadium(v) oxide (catalyst)/ vanadium oxide 7 (c) (i) SO 3 + H 2 O H 2 SO 4 (ii) fish harmed/ killed stonework eaten away/ OWTTE iron rusts (more quickly) (ii) max 2 Damages buildings (2) Total 11 marks 8 (a) (i) giant/regular structure/lattice of positive ions delocalised electrons/free electrons/sea of electrons/ (ii) can be beaten/hammered/rolled into (thinner) shape Nuclei Molecules/c ovalent/ioni c = 0/2 (iii) layers (of atoms/ions) slide over each other Molecules/c ovalent/ioni c = 0/2 25

26 8 (b) (shared/bonding) pair of electrons attracted to fluorine nuclei 8 (c) 2, (d) (ion) 2 and 8 or shown on diagram 2+ shown 8 (e) Mg ion / Mg 2+ has higher charge (than Na ion / Na + ) stronger attraction between ions/ stronger ionic bonds Total 13 marks 26

27 9 (a) decreases increases increases no change (4) 9 (b) rate increases (reactant) particles closer together/more particles in given volume molecules/particles collide more frequently/ more collisions per second Rate same/rate decreases = 0/3 If no mention of particles/molecules max 1 for explanation atoms 9 (c) recycled / put back into reactor Used again 9 (d) (i) oxidation / redox/ accept exothermic (ii) platinum / rhodium/ Pt/ Rh (iii) 2NO + O 2 2NO 2 all formulae correct balancing 27

28 9 (e) NH 4 NO 3 9 (f) phosphorus potassium Phosphate Total 15 marks 10 (a) brick red/ orange - red Red / orange 10 (b) water / H 2 O 28

29 10 (c) (i) M r = 74 n Ca(OH) 2 = = 0.2 (ECF) (ii) n HNO 3 = = 0.4 (ECF) V = = 0.25 (dm 3 ) = 250 cm 3 (iii) M r = 164 m = = 8.2 g Penalise 1 sf in (iii) 10 (d) Ca(NO 3 ) 2 + Na 2 CO 3 CaCO 3 + 2NaNO 3 all formulae correct balancing white precipitate/solid/ suspension accept ionic equation Total 12 marks 11 (a) (i) (on diagram) in left and + in right (ii) H + gain of electrons (iii) (on diagram) horizontal line in right-hand tube about halfway between given line and top of tube (explanation) for same number of electrons in I and II 2 moles/molecules of hydrogen formed for 1 mole/molecule of oxygen oh - = 0/2 If wrong level 0/3 29

30 11 (b) (i) 0.2(0) (ii) = 4.8 (dm 3 ) 11 (c) (i) 0.2(0) (ii) = 6.4 (g) Penalise 1 sf in ii Total 12 marks Paper total 120 marks 30

31 Paper 03 1 Acceptable Answers Variable to be measured Apparatus used time stop watch s mass balance Units of variable g / grams accept kg length rule cm / centimetres / mm volume burette cm3 / ml / centimetres cubed / cubic centimetres / millilitres temperature thermometer centigrade / Celsius / o C Mark (8) Total 8 marks 2 (a) amount metal carbonate / allow mass form/ surface oven/particle of size metal carbonate volume limewater / amount limewater size Bunsen flame / distance of tube from Bunsen/ temp or type of flame Max 2 (2) 2 (b) Repeated 31

32 2 (c) y scale labelled. Time (for limewater to turn cloudy) in seconds 4 bars of correct height indication of which bar is for which substance 2 (d) magnesium (carbonate) 2 (e) (i) measuring cylinder not vertical (ii) lower volume / reduces (iii) gas syringe 2 (f) (i) 15 (cm 3 ) 44 (cm 3 ) 29 (cm 3 ) (cq) (ii) 29 / 30 = 0.97 dividing answer to (i) by 30 correct to 2 sf (iii) middle box ticked Total 16 marks 32

33 3 (a) (i) directly proportional. Allow 1 mark for qualitative link (e.g. increasing volume, increasing time) (2) (ii) quantative link, such as twice as big means twice as much air/oxygen = 2 (2) qualitative bigger means more air/oxygen = 1 (iii) stop more air getting in 3 (b) fill with water and pour into measuring cylinder 3 (c) B / second one results closest together / repeats most similar 3 (d) 94 Anything else 33

34 3 (e) (i) suitable scales used (>half grid in both directions) points plotted correctly (-1 mark per error) straight line drawn; may go through origin or hit x- axis (2) (ii) point at 700 circled (cq on points) (iii) must correctly explain why time longer. e.g. spout not sealed air got in OR smaller flame/wick used up oxygen more slowly OR smaller candle more air in beaker OR bigger beaker more air (iv) more points below (f) (i) contains 5 x as much oxygen / air only 20% oxygen (must be quantitative) (ii) read correct value from graph correct multiplication by 5 Total 20 marks 34

35 4 (a) BOTH being sodium one carbonate one hydrogen carbonate 4 (b) (i) both Li and Sr give red flames both carbonate and hydroxide turn UI blue (ii) add (nitric) acid does NOT fizz Total 6 marks Paper total 50 marks 35

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