Mark Scheme (Results) November 2009

Transcription

1 Scheme (Results) November 2009 IGCSE IGCSE Chemistry (4335) Paper 2H Edexcel Limited. Registered in England and Wales No Registered Office: One90 High Holborn, London WCV 7BH 4335_F Nov 2009 i

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3 S E C T I O N A Question a M (electron) /836 / negligible Accept value in range /2000 to /800 and to Ignore zero M2 (neutron) 0 M3 (proton) M4 (proton) + b i M (number of) protons and neutrons M2 35 ii M 8 c i M 5 ii M isotopes TOTAL 9 Question 2 a M white M2 blue b i M fractional M2 distillation ii M different boiling points / boiling point of propanone lower than that of water iii M heat / boil M2 propanone boils/collects (first) M3 stop collecting liquid above 56 C Accept wording that indicates that water collected separately or not at all c M cross in column box 4 M2 cross in column 2 box 2 TOTAL 0

4 3 a M loses an electron/electrons M2 Na + b M gains two electrons M2 O 2 c M sodium oxide M2 Na 2 O TOTAL 6 Question 4 a M (bromine) liquid M2 grey / black b i M any indication of chlorine in left hand tube ii M hydrogen / H 2 iii M brine / sodium chloride solution / NaCl(aq) Accept concentrated/saturated NaCl Ignore sea water c i M chlorine + sodium bromide M reagents 2 M2 bromine + sodium chloride M2 products ii M displacement / redox Accept reduction / oxidation Ignore substitution iii M (chlorine) more reactive (than bromine) TOTAL _2H Nov

5 5 a M double bond / C=C / not all bonds are single b M contains bromine / another element/atom does not contain only carbon and hydrogen c M B and E d M A and B / A and E / C and F e M alkane(s) M2 C n H 2n+2 Accept other symbols such as x f M yellow / orange / brown M2 colourless / decolorised Ignore clear If only colourless stated, assume it is final colour g i M F ii M poly(ethene) / polyethene / polythene iii M addition TOTAL SECTION A TOTAL: 45 MARKS 4335_2H Nov

6 S E C T I O N B Question 6 a i M red Reject orange-red and brick red ii M Li + b M yellow M2 OH c i M melts / becomes a ball M2 moves (on surface) M2 Accept other words M3 fizzes / bubbles / effervescence indicating movement such as darts / whizzes / skids / skates / shoots M4 disappears / dissolves / becomes smaller M5 white trail Reject white precipitate Any two for each Ignore flames/fires ii M M all formulae correct 2Na + 2H M2 2 O 2NaOH + H 2 M2 balancing d i M flame / explosion Accept any more extreme observation from ci, eg moves more quickly, faster bubbling, but not just reacts faster/more violently ii M 0-4 / value within this range Reject range outside this, eg 9-2 TOTAL _2H Nov

7 7 a i M reagents wrong way round / in wrong places / calcium carbonate is solid and hydrochloric acid is liquid or solution ii M carbon dioxide denser/heavier than air M2 over water / in gas syringe / by downward delivery / upward displacement of air / have gas jar other way round iii M M2 M3 CaCO 3 (s) + 2HCl(aq) CaCl 2 (aq) + H 2 O(l) + CO 2 (g) b M bright/brilliant/dazzling/white flame/light M2 white solid Accept any wording that clearly suggests that calcium carbonate should be in the conical flask and hydrochloric acid in the funnel Do not penalise wrong terms for funnel, eg pipette/burette M correct formulae M2 balancing M3 state symbols M Accept burn instead of flame/light Do not accept glow/spark/flash M2 Accept other words in place of solid, eg smoke/ash/residue/d eposit/compound but not fumes/precipitate Accept in either order 4335_2H Nov

8 7 c i M strong (electrostatic) M Accept attractions/ionic bonds attractions/bonds hard to M2 between ions overcome/need much energy to overcome If atoms instead of ions, M can still score No marks if mention of molecules / covalent / sharing electrons / intermolecular ii M ions have greater/double charge(s) M Accept correct M2 stronger (electrostatic) comparison of either attractions/(ionic) bonds / cation or anion, eg attractions/bonds harder to Mg 2+ and Na + or O 2 overcome/need more energy to and Cl overcome No marks if mention of molecules / covalent / sharing electrons / intermolecular TOTAL _2H Nov

9 8 a M (J) coke / coal Ignore carbon / iron ore / iron oxide M2 (K) limestone Ignore chalk / marble / calcium carbonate Reject lime M3 (L) air Ignore oxygen b i M produces heat/energy / exothermic / raises the temperature ii M reducing agent / removes oxygen from Do not penalise iron oxide / converts iron oxide to iron reference to correct name or formula of any oxide of iron, eg iron(ii) oxide, Fe 3 O 4 iii M M reactants CaO + SiO 2 CaSiO 3 M2 M2 products Max if unbalanced c M calcium silicate / slag M2 less dense / lighter d M strong / hard / durable / malleable / ductile M2 catalyst / speeds up the reaction e i M (hydrated) iron (III) oxide Not any other oxide, and not just iron oxide ii M zinc more reactive (than iron) / higher in reactivity series / better reducing agent / better at losing electrons / transfers electron(s) to iron Ignore very reactive M2 reacts/corrodes/oxidises instead Ignore rusts of/before iron TOTAL _2H Nov

10 9 a i M M correct M2 Fe + 2HCl FeCl 2 + H 2 formulae M2 balancing ii M iron loses electrons and chlorine gains Accept correct electrons statement and M2 oxidation is loss and reduction is gain of definition for either electrons iron or chlorine for mark, eg iron loses electrons and is oxidised, or chlorine gains electrons and is reduced b M green precipitate/solid/suspension Ignore grey / dirty / bubbles M2 brown/rust precipitate/solid/suspension Accept orange / foxy red Ignore red Award mark for two correct colours with no mention of precipitate c i M Reject green / dark / (pale) blue deep Ignore bright ii M solution forms / precipitate dissolves Accept disappears Ignore liquid M2 colour darkens / goes dark/deep blue Accept royal blue iii M complex iv M silver nitrate / AgNO 3 (solution) M2 (dilute) nitric acid / HNO 3 M3 white precipitate/solid/suspension Do not award M3 if no mention of silver nitrate TOTAL _2H Nov

11 0 a M colourless If only one colour M2 pink / red given, assume it is the final colour If both colours correct but wrong way round, award mark b i M Correct final answer M scores 2 marks Ignore units Award for 4.2 Accept answers to 2 or more sf ii M CQ on bi M2 0.68(4) Correct final answer scores 2 marks Ignore units Accept answers to 2 or more sf c i M 85 Ignore units ii M CQ on bi and ci M (g) Accept answers to 2 or more sf Penalise incorrect units d M heat/boil/evaporate the solution M2 to crystallisation/saturation point / to If clear statement that remove some water all the water is M3 cool and filter / leave solution to evaporated by evaporate/dry heating, then M2 and M3 cannot be awarded OR M leave in warm place/on window ledge M2 for stated time M3 to allow water to evaporate / filter TOTAL _2H Nov 2009

12 a i M vapour/hydrocarbons/molecules/fractions /compounds / substances rise(s) / collect at different heights M2 condense/turn back to liquid (at different heights/temperatures) ii M heavier / bigger / greater M r M2 (fuel oil molecules) boil/condense at higher temperature iii M formula of type C x H y where x =5 to 2 and y = 2x or 2x + 2 iv M bitumen b i M C 4 H 30 ii M carbon-to-carbon/c C / C H bonds break Do not accept C=C bonds break M2 C=C bonds form If neither mark scored as shown, award mark for single bonds break and double bonds form c i M phosphoric acid / H 3 PO 4 ii M M Reactants C 2 H 4 + H 2 O CH 3 CH 2 OH / C 2 H 5 OH M2 M2 Product Max if unbalanced d i M redox / oxidation / reduction ii M ethanoic acid / ethanal TOTAL 4 SECTION B TOTAL: 75 MARKS PAPER TOTAL: 20 MARKS 4335_2H Nov

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