0620 CHEMISTRY - maxpapers.commaxpapers.com/wp-content/uploads/2012/11/0620_w15_ms_all.pdf · 0620/11 Paper 1 (Multiple Choice), maximum raw mark 40 ... Page 2 Mark Scheme Syllabus

® IGCSE is the registered trademark of Cambridge International Examinations.

CAMBRIDGE INTERNATIONAL EXAMINATIONS

Cambridge International General Certificate of Secondary Education

MARK SCHEME for the October/November 2015 series

0620 CHEMISTRY

0620/11 Paper 1 (Multiple Choice), maximum raw mark 40

Mark schemes should be read in conjunction with the question paper and the Principal Examiner Report for Teachers. Cambridge will not enter into discussions about these mark schemes. Cambridge is publishing the mark schemes for the October/November 2015 series for most Cambridge IGCSE

®, Cambridge International A and AS Level components and some

Cambridge O Level components.

Page 2 Mark Scheme Syllabus Paper

Cambridge IGCSE – October/November 2015 0620 11

© Cambridge International Examinations 2015

Question Number

Key Question Number

Key

1 B 21 B

2 A 22 D

3 C 23 C

4 C 24 A

5 D 25 A

6 D 26 A

7 A 27 C

8 B 28 C

9 A 29 D

10 C 30 C

11 A 31 C

12 A 32 B

13 D 33 B

14 C 34 A

15 D 35 B

16 D 36 D

17 A 37 A

18 C 38 A

19 D 39 C

20 C 40 A





0620 CHEMISTRY








Question Number

Key Question Number

Key

1 B 21 B

2 C 22 C

3 A 23 C

4 C 24 A

5 D 25 B

6 D 26 C

7 C 27 C

8 D 28 D

9 A 29 D

10 D 30 C

11 B 31 A

12 D 32 B

13 D 33 B

14 A 34 A

15 D 35 B

16 C 36 D

17 A 37 C

18 B 38 A

19 C 39 B

20 B 40 C





0620 CHEMISTRY








Question Number

Key Question Number

Key

1 A 21 B

2 B 22 D

3 B 23 A

4 D 24 A

5 D 25 A

6 D 26 A

7 C 27 C

8 C 28 D

9 A 29 D

10 C 30 B

11 B 31 B

12 A 32 B

13 D 33 B

14 D 34 A

15 C 35 A

16 B 36 D

17 A 37 D

18 B 38 A

19 D 39 C

20 B 40 A





0620 CHEMISTRY

0620/21 Paper 2 (Core Theory), maximum raw mark 80

This mark scheme is published as an aid to teachers and candidates, to indicate the requirements of the examination. It shows the basis on which Examiners were instructed to award marks. It does not indicate the details of the discussions that took place at an Examiners’ meeting before marking began, which would have considered the acceptability of alternative answers. Mark schemes should be read in conjunction with the question paper and the Principal Examiner Report for Teachers. Cambridge will not enter into discussions about these mark schemes. Cambridge is publishing the mark schemes for the October/November 2015 series for most Cambridge IGCSE






Abbreviations used in the Mark Scheme

• ; separates marking points

• / separates alternatives within a marking point

• () the word or phrase in brackets is not required but sets the context

• A accept (a less than ideal answer which should be marked correct)

• I ignore (mark as if this material were not present)

• R reject

• ecf credit a correct statement that follows a previous wrong response

• ora or reverse argument

• owtte or words to that effect (accept other ways of expressing the same idea)




Question Answer Marks

1(a)(i) F / barium chloride / BaCl2; 1

1(a)(ii) D / ammonium sulfate / (NH4)2SO4; 1

1(a)(iii) A / Al / Al2Cl6 / aluminium chloride; 1

1(a)(iv) E / HCl / hydrogen chloride; 1

1(a)(v) B / water / H2O; 1

1(a)(vi) C / methane / CH4; 1

1(b)(i) arrow under the aluminium foil; 1

1(b)(ii) fume cupboard; 1

1(b)(iii) 3 (Cl2); 1


2(a) make sure temperature change is the same throughout / make sure that there are no hot spots / no local heating; 1

2(b) any two from:

• same amount of solid / same mass of solid;

• same volume of water;

• same amount of stirring;

2

2(c)(i) Q 1

2(c)(ii) R; T; 2

2(d)(i) 235U; 1

2(d)(ii) 138; 1

2(d)(iii) cancer treatment / tracer / test thyroid function; 1

2(e)(i) kerosene; 1

2(e)(ii) C5H10; 1





3(a) 2 (Ni); CO2 (on right);

1 1

3(b)(i) positive electrode / anode in box on left; negative electrode / cathode in upper box on right; electrolyte / named suitable electrolyte in lower box on right; 3 correct = [2] 1 or 2 correct = [1]

1 1

3(b)(ii) cathode / negative electrode; 2

3(c)(i) the positive electrode: chlorine; the negative electrode: nickel;

1

3(c)(ii) inert / unreactive; conducts electricity;

1 1

3(d)(i) giant structure / lots of carbon atoms joined to each other / lattice of covalent bonds; strong (covalent) bonds throughout;

1 1

3(d)(ii) weak forces between layers; layers can slide (over each other);

1 1


4(a)(i) gradient / slope is greater for strontium ora; 1





4(a)(ii) 11 (cm3); 1

4(a)(iii) 64–66 (s); 1

4(a)(iv) the line was still going up / the line was still rising; 1

4(a)(v) (rate) increases; 1

4(b)(i) (volumetric) pipette; 1

4(b)(ii) to show end point of titration / to show when the solution has been neutralised; litmus goes from blue to pink (at end point);

1 1

4(c)(i) decreases slowly at first; then sudden decrease in pH; then slow decrease;

1 1 1

4(c)(ii) 26 (cm3); 1

4(c)(iii) strontium chloride; 1





5(a) melting / ice melts / ice goes from solid to liquid; any four from:

• in solid particles regularly arranged;

• in solid particles arranged in fixed position / cannot move;

• particles in solid absorb energy;

• particles (in solid) vibrate more / particles start to move when heated;

• forces between particles (in solid) broken;

• particles in liquid slide over each other / move;

• particles in liquid not regularly arranged;

1

4





5(b)(i) coolant / for making ethanol / for making specified chemicals / solvent; 1

5(b)(ii) washing / cooking / cleaning etc.; 1

5(c)(i) lithium + water → lithium hydroxide + hydrogen; 1

5(c)(ii) any two from:

• floats on surface (of water);

• bubbles of gas;

• fizzes / fizzing sound;

• decreases in size / disappears;

• moves around;

2

5(c)(iii) (potassium) more reactive / lithium less reactive; 1

5(d)(i) correct structure of ethene; 1

5(d)(ii) high temperature; catalyst / phosphoric acid;

1 1

5(e) cobalt → iron → cerium → calcium; one pair reversed or all reversed = [1]

2


6(a) C5H8; 1





6(b) bromine / bromine water / aqueous bromine; decolourised / goes from orange to colourless;

1 1

6(c)(i) double bond; 1

6(c)(ii) poly(ethene) / any other addition polymer; 1

6(d) it is a molecule / covalent compound; 1

6(e) any two from: carbon or soot / carbon monoxide / water; 2

6(f) alcohols / first box ticked; 1


7(a) any five from:

• 11 electrons;

• electrons – (negatively) charged;

• electrons outside nucleus in shells;

• nucleus contains protons and neutrons;

• protons – (positively) charged;

• neutrons no charge;

• 11 protons;

• 12 neutrons;

• electron arrangement 2,8,1 / 1 electron in outer shell;

5

7(b)(i) 2 (NaOH); 2 (H2O);

1 1

7(b)(ii) substance containing carbon and hydrogen only / substance containing carbon and hydrogen and no other element; 1

7(b)(iii) 70; 1





0620 CHEMISTRY














• R reject








1(a)(i) E / NO2 / nitrogen dioxide; 1

1(a) (ii) B; 1

1(a)(iii) C / NaI / sodium iodide; 1

1(a)(iv) E / NO2 / nitrogen dioxide; 1

1(a)(v) D / F2 / fluorine; 1

1(a)(vi) C / NaI / sodium iodide; 1

1(b) substance containing only one type of atom / substance which cannot be broken down further by chemical means; 1

1(c) O2; 4 (HF);

11


2(a) any two from:

• (same) volume of water;

• (same) distance of flame from beaker;

• (same) height of flame;

2

2(b) exothermic and heat released / heat given out; 1

2(c)(i) hexane; 1

2(c)(ii) hexane; 1

2(d)(i) correct structure of methane; 1

2(d)(ii) natural gas; 1

2(e)(i) both end in –ane; 1

2(e)(ii) compounds; properties; functional;

3





3(a)(i) gives off bubbles rapidly / fast / many bubbles; disappears quickly;

11

3(a)(ii) zinc; 1

3(a)(iii) too reactive / high in the electrochemical / reactivity series; 1

3(b) oxygen removed from barium oxide / it loses oxygen; 1

3(c)(i) use pH meter and pH above 7 / (red) litmus turns blue; 1

3(c)(ii) barium chloride; water;

11

3(d)(i) burette; 1

3(d)(ii) any two from:

• starts off at high / alkaline pH / pH above 7;

• pH decreases / gets more acidic / less alkaline / becomes neutral;

• ends up at acidic pH / pH below 7;

2

3(e) two electrodes dipping into the electrolyte; electrodes correctly connected to battery / power supply; correct labels for electrodes and power supply battery;

111


4(a)(i) measure volume of gas / measure amount of gas; gas collected in the measuring cylinder; at different times / use of stopclock to measure time;

111

4(a)(ii) faster reaction / rate increases; 1

4(b)(i) same concentration of acid; same mass of iron; same size of iron pieces;

111





4(b)(ii) rate increases with increase in temperature rate increases with temperature = [1]

2

4(c) any three from:

• filter (off the iron);

• evaporate water / heat gently;

• to crystallisation point / leave to cool (after heating);

• filter off / pick out crystals;

• dry crystal between filter papers;

3


5(a) any four from:

• in solid particles regularly arranged;

• in solid particles arranged in fixed position / cannot move or vibrate;

• particles close together in solid;

• particles in liquid slide over each other / move;

• particles in liquid not regularly arranged;

• particles close together in liquid;

4

5(b)(i) any two from:

• fossil fuels contain sulfur / named fossil fuel contains sulfur;

• burning fossil fuel;

• sulfur reacts with oxygen / sulfur reacts with air;

• sulfur dioxide is a gas (so escapes into air);

2

5(b)(ii) acidic / acid; 1

5(b)(iii) calcium oxide / calcium carbonate; reacts with (moist) sulfur dioxide / reacts with acidic gas / forms calcium sulfite;

11

5(b)(iv) 2 (H2O) on right; 2 (H2SO4) on left;

11





5(c) any two from:

• conducts heat / conducts electricity;

• malleable;

• ductile;

• lustrous / shiny surface;

2

5(d)(i) aluminium is good conductor; steel is strong / core is strong;

11

5(d)(ii) copper is cheap(er) (than silver) / silver is (more) expensive; 1


6(a)(i) ring around OH group; 1

6(a)(ii) unsaturated and has double bonds; 1

6(b)(i) condenser; 1

6(b)(ii) any characteristic of a mixture, e.g. can be separated by physical means / has variable composition / properties are the average of those of the components;

1

6(b)(iii) geraniol floats on top of the water; 1

6(c)(i) structure of ethanol drawn correctly with all atoms and bonds; 1

6(c)(ii) carbon dioxide; water;

11

6(d) 21%; 1





7(a) any five from:

• four electrons;

• electrons negatively charged;

• electrons outside nucleus in shells;

• nucleus contains protons and neutrons;

• protons positively charged;

• neutrons no charge;

• four protons;

• five neutrons;

• electron arrangement [2,2] / two electrons in outer shell;

5

7(b) BeCl 2; 1

7(c)(i) 43 correct atomic masses only = [1]

2

7(c)(ii) global warming / greenhouse effect / effect of global warming, e.g. rise in sea level / desertification / more extreme weather / climate change;

1





0620 CHEMISTRY














• R reject








1(a)(i) B / Cl2 / chlorine; 1

1(a)(ii) C / N2 / nitrogen; 1

1(a)(iii) E / Ar / argon; 1

1(a)(iv) A / ethene / C2H4; 1

1(a)(v) A / ethene / C2H4; 1

1(a)(vi) F / CO2 / carbon dioxide; 1

1(b) substance containing (two or more) different atoms bonded / substance containing (two or more) different atoms combined; 1

1(c) in light bulbs / as an inert atmosphere / welding; 1

1(d) 3 (Mg) and N2; 1


2(a)(i) plastics; 1

2(b) third box ticked / exothermic; 1

2(c) 4; 1

2(d)(i) speed up the reaction / increase reaction rate; 1

2(d)(ii) carbon dioxide; water;

11

2(e) any two from: • sulfur (oxidises / burns) to form sulfur dioxide; • acid rain / acidic gas formed; • effect of acid rain, e.g. kills animals in ponds (or lakes) / kills plants / soil demineralisation / erodes limestone buildings / iron

structures corroded;

2

2(f)(i) alkane(s); 1

2(f)(ii) colourless / liquid at room temperature / low melting point; 1





2(f)(iii) O ║ C – O – H; 1


3(a) flask; Bunsen burner / Bunsen / burner;

11

3(b) sodium sulfate; 1

3(c)(i) 3 correctly labelled = [2] 1 or 2 correctly labelled = [1];

2

3(c)(ii) X = chlorine / Cl2; Y = hydrogen / H2;

11

3(c)(iii) calcium chloride; carbon dioxide; water; 3

3(d)(i) 1.6; 1

3(d)(ii) idea that pH increases slowly at first ; idea of sudden increase at around 18 cm3 ; idea of pH increasing at a slower rate in the more alkaline region;

111





4(a) measure the volume of gas; in a (measuring) cylinder; at different times;

111

4(b)(i) increases then decreases; comment on the curve, e.g. rate not constant at first / peak (or maximum) at 60 hours / rate of decrease less than rate of increase (around the maximum);

11

4(b)(ii) 0.29 (cm3 CO2 per hour); 1

4(b)(iii) any two from: • higher temperature (R: temperatures above 40 °C); • increase concentration of glucose; • increase amount of yeast;

2

4(c) M1 correct method, e.g. add litmus / add sodium hydroxide / add sodium carbonate / measure pH; M2 correct outcome, e.g. litmus turns red with acid / no change of litmus with ethanol / pH below 7 with acid / pH 7 with ethanol / acid reacts with sodium hydroxide or sodium carbonate / ethanol does not react with sodium hydroxide or sodium carbonate;

11


5(a) any four from: • particles in the liquid slide over each other / move slowly / restricted movement; • particles in the liquid not regularly arranged / randomly arranged; • particles close together in liquid; • in the gas particles arranged randomly / are anywhere; • in the gas particles move from place to place / move freely / move fast; • particles far apart in the gas;

4

5(b)(i) liquid; temperature above melting point but below boiling point;

11

5(b)(ii) copper and iron; both have high melting points ;

11





5(b)(iii) resistant to corrosion; 1

5(c)(i) oxygen / air; water;

11

5(c)(ii) idea of layer stopping air or water getting to the surface / idea of blocking reaction with the surface of the iron, e.g. stops air or oxygen getting to surface / blocks water or moisture getting to the iron;

1

5(d)(i) iron chloride / iron(II) chloride; hydrogen;

11

5(d)(ii) M1 (aqueous) sodium hydroxide / (aqueous) ammonia; M2 green precipitate / grey-green precipitate;

11

5(e) any suitable use, e.g. cutlery / chemical plant / surgical instruments / saucepans; 1


6(a) fractional distillation / fractionation / fractionating; differences in boiling point(s);

11

6(b)(i) refinery gas; 1

6(b)(ii) kerosene / paraffin; 1

6(c)(i) B and C / ethene and propene; 1

6(c)(ii) H2; C3H6;

11

6(d)(i) copper; 1

6(d)(ii) it is cooler / temperature lower; 1





7(a) any five from: • 17 protons; • 18 neutrons; • 17 electrons; • protons positively charged; • neutrons no charge • electrons negatively charged; • electrons outside the nucleus in shells; • nucleus contains protons and neutrons; • electron arrangement 2, 8, 7 / 7 electrons in the outer shell;

5

7(b) sodium atoms each lose an electron / sodium has one more proton than electrons; chlorine atoms each gain an electron / chlorine has one more electron than protons;

11

7(c)(i) iodine formed; 1

7(c)(ii) chlorine is more reactive than iodine / chlorine is higher in the reactivity series than iodine; 1

7(d)(i) C2ClF5; 1





0620 CHEMISTRY

0620/31 Paper 3 (Extended Theory), maximum raw mark 80













• R reject








1(a)(i) Na+ / sodium and O2–

/ oxide; 1

1(a)(ii) Ca2+ / calcium; 1

1(a)(iii) P / phosphorus; 1

1(a)(iv) Si / silicon; 1

1(b)(i) • number of protons = 29;

• number of neutrons = 35;

• number of electrons = 27;

three correct = [2]; two correct = [1]

2

1(b)(iii) number of nucleons = 45; number of charged particles = 42;

11

1(c)(i) have same proton number / same element / same atomic number; different number of neutrons / nucleons / mass number;

11

1(c)(ii) magnesium / Mg; 1

1(c)(iii) any two from:

• treating cancer or radiotherapy;

• biological tracer;

• thickness (of paper or foil);

• (checking for) leaks / cracks (in pipes);

• (carbon) dating;

• (generating) energy / electricity;

• smoke detectors;

• fill levels in packages;

• sterilising surgical instruments;

2





2(a) add a (dilute) acid; filter; copper does not react or dissolve / zinc reacts or dissolves or forms a salt;

111

2(b) diffusion (through a membrane); nitrogen diffuses faster; because it has the smaller Mr; or (turn into) liquid; (fractional) distillation; different boiling points; or burn a named substance to make non-gaseous product; oxygen reacts / nitrogen does not react; name of product of combustion;

3

2(c) chromatography; use a locating agent / the two acids move at different rates / alanine travels faster / alanine higher up paper / travels further;

11

2(d) add sodium hydroxide solution; filter; zinc hydroxide (is amphoteric it) will react or will dissolve / magnesium hydroxide does not react or does not dissolve;

111





3(a) fast(er) reaction; large(r) surface area;

11

3(b) 4.76 (dm3); 1

3(c) moves equilibrium to right; increases yield (of sulfur trioxide) / uses up more sulfur dioxide;

11

3(d)(i) moves equilibrium to left; (forward reaction) exothermic;

11

3(d)(ii) decrease rate; molecules have less energy / move slower; fewer collisions (per second) / fewer particles have the activation energy / fewer collisions have the activation energy;

111

3(e)(i) moves to right; 1

3(e)(ii) high yield at 2 atm; 1

3(f) vanadium(V) oxide / vanadium pentoxide; 1

3(g) M1 dissolve / react sulfur trioxide in (concentrated) sulfuric acid; add water to product of M1;

11


4(a)(i) any two from:

• shortage of sites / landfill sites fill up;

• visual pollution / litter;

• danger to wild life;

2

4(a)(ii) (produce) toxic gases or CO or HCl or HF / carbon dioxide / greenhouse gases; 1

4(b) any two from: bags / clothing or specified clothing / packaging / bowls / cups / plates / flooring / carpets / pipes / insulation / non-stick coatings / ropes;

1





4(c)(i) CH2=CHCH3 double bond is shown; rest of structure correct;

2

4(c)(ii) ester; 1

4(c)(iii) (carboxylic) acid; alcohol;

11

4(d) addition – polymer only product / only one product; condensation – (polymer and) simple molecule / water / hydrogen chloride made; polymer A is an addition polymer and polymer B is a condensation polymer;

111


5(a)(i) adds up to 100%; 1

5(a)(ii) M1 55.85/12 and 6.97(/1) and 37.2/16; or evaluation 4.650 6.970 2.325; M2 C2H3O; correct answer with no working = [2]

1

1

5(a)(iii) M1 (86/)43; M2 C4H6O2; correct answer with no working = [2]

11

5(b)(i) unsaturated / C=C double bond / alkene; 1

5(b)(ii) (organic / carboxylic) acid / contains or releases H+ ions; 1

5(b)(iii) CH3CH=CHCOOH / CH2=CHCH2COOH / CH2=CH(CH3)COOH; 1





6(a)(i) any three from:

• each oxygen is joined to two silicons / atoms;

• each silicon is joined to four oxygens / atoms;

• tetrahedral (around silicon) / similar to diamond;

• linear around oxygen;

3

6(a)(ii) any three from:

• high melting point / boiling point;

• hard;

• strong;

• (colourless) crystalline (solid);

• brittle / not malleable;

• poor / non-conductor (of electricity) / insulator;

• insoluble (in water);

3

6(a)(iii) SiO2 does not react with or dissolves in or neutralise an acid or acidic oxide; SiO2 does react with or dissolve in or neutralise an alkali or base or basic oxide;

11

6(b) carbon dioxide has a simple molecular structure; 1





7(a)(i) step 2 and it is electron gain / oxidation state decreases; 1

7(a)(ii) silver (ion) and it accepts electrons / gets reduced / oxidation state decreases; 1

7(b) prediction: the ‘not covered’ section will be black; the ‘covered in thick card’ section will be white / cream; the ‘covered in thin card’ section will be grey; explanation: the more light, the more silver ions are reduced;

111

1

7(c)(i) carbon dioxide + water → glucose + oxygen reactants correct; products correct;

11

7(c)(ii) chlorophyll; 1

7(c)(iii)

one correct –O– link between rectangles; two correct glucose units with continuation bonds;

11

7(c)(iv) the reaction of glucose with oxygen to release (carbon dioxide and water and) energy; or the reaction of glucose in a biological system to release energy;

1





0620 CHEMISTRY














• R reject








1(a)(i) NF3; 1

1(a)(ii) P2S3; 1

1(b)(i) Se2–; 1

1(b)(ii) Ga3+; 1

1(c)(i) Cr2(SO4)3; 1

1(c)(ii) Ba(OH)2; 1


2(a)(i) combustion / burning of a motor vehicle fuel or a named fuel which can act as a motor vehicle fuel; incomplete combustion would produce CO; complete combustion would produce CO2;

3

2(a)(ii) carbon dioxide: climate change / global warming / greenhouse effect; carbon monoxide: poisonous / toxic;

2

2(a)(iii) nitrogen and oxygen react or combine; at high temperatures or in presence of spark;

2

2(a)(iv) it reacts or combines with oxygen / NO + ½O2 → NO2; 1

2(b) any two from:

• acid rain is formed;

• lowers pH or acidifies lakes / rivers or kills fish / aquatic animals;

• changes composition of soils or reduces fertility of soil or reduces crop yields / deforestation or kills crops or trees or plants or leaves / lowers pH of soil or increases acidity of soil;

• attacks (limestone) buildings or statues; attacks metal (structures) / bridges;

2





2(c) use of a catalytic converter; 2NO + 2CO → 2CO2 + N2 species; balancing;

3


3(a) zinc blende is burnt / roasted / heated in air; zinc sulfide + oxygen → zinc oxide + sulfur dioxide;

2

3(b) zinc oxide + carbon → zinc + carbon dioxide / monoxide; 1

3(c) zinc sulfate; pure zinc;

Zn2+ + 2e– → Zn;

Zn → Zn2+ + 2e–; zinc ions are removed (from solution) and replaced (into solution); at the same rate / speed;

6

3(d)(i) copper; 1

3(d)(ii) any two from:

• hard(er) / less malleable;

• strong(er);

• (better) appearance;

• (more) resistant to corrosion;

2

3(e)(i) steel (or iron) is exposed to oxygen and water; 1

3(e)(ii) Zn more reactive than Fe (allow steel); Zn loses / transfers electrons (more readily) and forms (+ve) ions (in preference to Fe); Fe (allow steel) is more reactive than Cu; Fe loses / transfers electrons (more readily) and forms (+ve) ions (in preference to Cu);

4





4(a)(i) a reaction whose rate is influenced by light / reaction which occurs in presence of light; 1

4(a)(ii) CH3CHClCH3; 1

4(a)(iii) (both have) same molecular formula; different structural formula or structure;

2

4(b) M1 bonds breaking = (8 × 412) + (2 × 348) + 242 = 4234;

M2 bonds forming = (7 × 412) + (2 × 348) + 338 + 431 = 4349; M3 4234 – 4349 = –115 and exothermic;

3

4(c)(i) CH3CH2CH2Cl + NaOH → CH3CH2CH2Cl + NaCl NaCl as product; rest of equation;

2

4(c)(ii) propene; CH2=CHCH3;

2

4(c)(iii) propanoic acid; 1

4(d)(i) 46; 1

4(d)(ii) 60; 1

4(d)(iii) moles of CH3CH2CH2OH = 0.1; moles of HCOOH = 0.087 (0.09) and limiting reagent is methanoic acid;

2

4(d)(iv) 88 × (mol of limiting reagent in 4(d)(iii));

expected answer: 88 × 0.087 = 7.65 g;

1





5(a) as a reducing agent; source of heat / energy;

2

5(b) Fe2O3 + 3CO → 2Fe + 3CO2

species; balancing;

2

5(c) silica reacts with limestone or calcium oxide; to form a slag or calcium silicate or CaSiO3; (liquid) slag floats (above molten iron);

3

5(d) blow or pass oxygen through (molten) iron; C + O2 → CO2; carbon dioxide escapes or carbon dioxide is a gas;

3


6(a) the number of e– gained or lost = numerical value of oxidation state; any two from:

• Na to Al (Si) lose e–;

• (Si) P to Cl gain e–;

• Si gains and loses e– / Ar neither gains nor loses e–;

1

2

6(b) M1 positive ions / cations / metallic ions; the (correct) particles named in M1 are arranged in a lattice / rows / layers; sea of electrons / delocalised electrons;

3

6(c) they have mobile electrons; 1

6(d) chlorine; 1

6(e) strong covalent bonds ; in a giant lattice / macromolecule / giant (structure);

2





6(f) any two from:

• sodium chloride is ionic and PCl 3 is covalent;

• ionic bonds are strong and intermolecular forces are weak;

• PCl 3 reacts with water and NaCl does not;

2

6(g) MgO will react with / dissolve in / neutralise hydrochloric acid / acid / acid oxide; if amphoteric, MgO will react with or dissolve in or neutralise hydrochloric acid or acid or acid oxide and MgO will react with dissolve in or neutralise sodium hydroxide or alkali or base or basic oxide; MgO will not react with or dissolve in or neutralise sodium hydroxide or alkali or base or basic oxide = [2]

2

6(h)

Mg

x

x

x

2+

x

x x

x

x O

2-

x

x

magnesium with 8 or 0 outer shell electrons; oxygen with 8 outer shell electrons and 2 indicated differently from the other 6 and these 2 electrons must match the Mg electrons if these have been shown; correct charges;

3





0620 CHEMISTRY














• R reject








1(a) cobalt chloride (paper) / anhydrous cobalt chloride / CoCl 2;

from blue; to pink;

or copper sulfate / anhydrous copper sulfate / CuSO4; from white; to blue;

3

1(b) boils at 100 °C / boiling point 100 °C / freezes at 0 °C / freezing point 0 °C / melts at 0 °C / melting point 0

oC; 1

1(c) any two from:

• filtration / sedimentation / sieving / screening / (pass through) gravel (beds) / flocculation / decantation / clarification / coagulation / flotation / settling tank / add aluminium sulfate;

• (add) carbon;

• chlorination / (add) chlorine / add Cl 2;

• fluoridation / add fluoride;

• ozone dosing;

• desalination;

• aeration;

• distillation;

2

1(d) any two from: making steel; making paper; textiles; generating electricity / energy / power / turbines; HEP; water mills; steam power (e.g. steam engines); geothermal power; agriculture; livestock; irrigation; hydration of alkenes / manufacture of ethanol / alcohols; manufacture of sulfuric acid / Contact process; manufacture of hydrogen; solvent / dissolving; coolant / cooling; cleaning / washing; (supply of) drinking (water); central heating; production of slaked lime; cooking;

2





2(a) sulfur dioxide / SO2; 1

2(b) hydrogen / H2; 1

2(c) ethene / C2H4; 1

2(d) argon / Ar; 1

2(e) carbon monoxide / CO; 1

2(f) methane / CH4; 1


3(a)(i) vibrate (about fixed position) / vibration; 1

3(a)(ii) electrostatic force of) attraction; (between) positive ions and negative ions / oppositely charged ions / unlike charged ions / cations and anions;

1

1

3(a)(iii) regular / repeated / pattern / framework / ordered / alternating / organised (arrangement of); positive and negative ions / oppositely charged ions / cations and anions / unlike charged ions;

1

1

3(b)(i) correct direction (going towards negative electrode); 1

3(b)(ii) Li+ + e– → Li / Li+ → Li – e–; 1

3(b)(iii) 2Br– → Br2 + 2e– / 2Br– – 2e– → Br2

formulae; balancing;

2

3(b)(iv) Br– / bromide (ion);

electron lost / donated electrons / increased oxidation state / increased oxidation number / oxidation numbers changed from –1 to 0 / increased valency;

1

1





3(c) M1 (gas) hydrogen (given off at cathode) / H2; M2 hydroxide ions / lithium hydroxide / OH–

/ LiOH are alkali(ne);

M3 2LiBr + 2H2O → 2LiOH + H2 + Br2; or

2H+ + 2e– → H2 / 2H+ → H2 – 2e–; or

2Br– → Br2 + 2e– / 2Br– – 2e– → Br2;

or

2H+ + 2Br– → H2 + Br2;

3


4(a)(i) any three from:

• (same) general (molecular) formula;

• (consecutive members) differ by CH2;

• same functional group;

• common (allow similar) methods of preparation;

• same / similar chemical properties / (chemical) reactions;

3

4(a)(ii) CnH2n alkene; CnH2n+2 alkane;

1

1

4(a)(iii) alkanes all or only (C–C) single bonds / no double bonds / no multiple bonds; alkenes (at least one) C=C / double bond / multiple bond;

1

1

4(b)(i) heat / high temperature / temperature between 450 °C and 800 °C; catalyst / named catalyst, e.g. zeolites or alumina or aluminium oxide or aluminosilicates or silica or oxides of chromium; or high pressure / pressure in range of 2–70 atm; or steam; absence of air / oxygen;

2

4(b)(ii) any correct equation producing an alkane and an alkene adding up to seven carbon atoms in the products; 1





4(b)(iii) any correct equation producing two alkenes and hydrogen, e.g. → C2H4 + C5H10 + H2 / C3H6 + C4H8 + H2; 1

4(b)(iv) alkenes: more useful than alkanes / used to make polymers or plastics / used to make chemicals / petrochemicals; or alkanes: (balance the demand for different) fuels / increase petrol (fraction) or hydrogen / produce lighter fractions from heavier fractions or suitable example, e.g. naphtha to gasoline / more useful smaller molecules or more demand for smaller molecules or more demand for smaller fractions / used as fuel / used to make ammonia / used in Haber process / used in hydrogenation of vegetable oils / used to make HCl ;

1

1

4(c)(i) 150 (cm3); 1

4(c)(ii) 100 (cm3); 1

4(c)(iii) This question was discounted. 1


5(a)(i) proton donor / H+ donor / hydrogen ion donor; 1

5(a)(ii) strong acid completely or fully ionises / completely or fully dissociates / completely or fully splits into ions; weak acid partially or incompletely ionises or dissociates or splits into ions / does not ionise fully;

1

1

5(b)(i) barium sulphite / barium sulfate(IV) / BaSO3; 1

5(b)(ii) barium sulfate / BaSO4; 1

5(b)(iii) Br2 + 2e– → 2Br– / Br2 → 2Br– – 2e–; 1

5(b)(iv) sulfuric acid; 1

5(c)(i) (→) magnesium sulfate + water; 1

5(c)(ii) (→) zinc sulfate + hydrogen; 1

5(c)(iii) (→) copper(II) sulfate / copper sulfate + carbon dioxide + water; 1

5(d)(i) 2NH3 + H2SO4 → (NH4)2SO4 / NH3 + H2SO4 → (NH4)HSO4; 1





5(d)(ii) 2NaOH + H2SO4 → Na2SO4 + 2H2O Na2SO4; rest of equation correct; or H+ + OH– → H2O H2O as the only product on the right hand side; rest of equation correct; or NaOH + H2SO4 → NaHSO4 + H2O NaHSO4; rest of equation correct; or OH– + H2SO4 → HSO4

– + H2O HSO4

–; rest of equation correct;

2

5(d)(iii) Fe + H2SO4 → FeSO4 + H2; FeSO4; rest of equation correct; or Fe + 2H+ → Fe2+ + H2; Fe2+; rest of equation correct; or 2Fe + 3H2SO4 → Fe2(SO4)3 + 3H2; Fe2(SO4)3; rest of equation correct; or 2Fe + 6H+ → 2Fe3+ + 3H2; Fe3+; rest of equation correct;

2





6(a) Na / sodium and Li / lithium; 1

6(b) Cu / copper and Rh / rhodium; 1

6(c) Fe2(SO4)3; 1

6(d) Mg2+; 1

6(e) copper sulfate (solution); add manganese / Mn to solution; copper displaced or forms / blue colour changes; or (a solution of) an iron salt or a zinc salt; add copper and manganese to each; only manganese reacts / displaces; or (a solution of a) manganese salt and a copper salt; add, e.g. iron / zinc; copper (displaced) and manganese not; or to a (dilute) acid / any named acid / water / steam; add Mn and Cu / both metals to the liquid; rate faster or shorter time or more bubbles or more hydrogen or more gas with Mn or with the more reactive metal / reaction only with Mn or with the more reactive metal; or copper oxide; add manganese and heat; evidence of reaction; or burn manganese and copper / both elements; in air / oxygen; Mn or more reactive metal burns brighter / only Mn or more reactive metal burns / evidence that manganese reacts faster; or add carbon; to both metal oxides and heat; evidence that reaction occurs with copper oxide more readily / least reactive metal oxide;

3





or both metal nitrates or carbonates; heat; evidence that manganese compound is most stable / most reactive compound is most stable; or (electrochemical) cell / use of voltmeter / electrolyte; copper and manganese (as electrodes); manganese is the negative terminal;

6(f) physical properties any three from: hard; strong; high density; malleable; ductile; sonorous; shiny; high melting point / high boiling point; (good) conductor (of heat/electricity); forms coloured compounds / coloured ions / coloured salts; chemical properties any two: catalytic behaviour; more than one or different or variable oxidation state or oxidation number or valency / variable charges / many differently charged ions; forms complex (ions); forms coloured compounds / coloured ions / coloured salts; amphoteric oxide / amphoteric / basic oxide / alkaline oxides / acidic oxide; (other metallic reactions) with acids / water / steam; reducing agent / electron donor / reacts with non-metal to form ionic compound / forms positive ions;

5





7(a) moles of KOH used ( = 0.025 × 2.53 =) 0.06325 / 0.063; number of moles of H2SO4 needed to neutralise the KOH = 0.031625 / 0.032; concentration of dilute sulfuric acid = 1.121/1.1 (mol / dm3);

3

7(b)(i) repeat experiment using same volume / amount of (same) H2SO4; and same volume / amount of (same) KOH; or (add activated) charcoal / carbon; filter out the charcoal; or mix volumes / amounts of H2SO4 and KOH in the ratio 1:2; of the same concentration;

2

7(b)(ii) make solution of potassium sulfate as above; add same volume / amount of acid again; or same volume / amount of KOH; add double the volume / amount of H2SO4; 25 cm3 KOH + 56.4 cm3 H2SO4 = [2] or same volume / amount of H2SO4; add half the volume / amount of KOH; 12.5 cm3 KOH + 28.2 cm3 H2SO4 = [2] or mix equal volumes / amounts of H2SO4 and KOH ; of the same concentration; mix solutions containing equal numbers moles of KOH and H2SO4 = [2]

2





7(c) test: reactive metal / name or formula of suitable metal, e.g. Mg / Fe / Zn; result: bubbles or gas or hydrogen or H2 evolved / dissolves; test: insoluble carbonate or name / formula of suitable insoluble carbonate, e.g. CaCO3; result: bubbles or gas or carbon dioxide or CO2 evolved / dissolves provided that carbonate is insoluble; test: alkali or name / formula of suitable alkali, e.g. NaOH / KOH; result: temperature change; test: alkali or name / formula of suitable alkali, e.g. NaOH / KOH and indicator; result: colour change; test: insoluble base or name / formula of suitable insoluble base; result: dissolves; test: indicator, e.g. blue litmus; result: colour change (colour need not be specified); test: measure pH / pH paper / UI paper / pH meter; result: pH 0–3 or indicator red / orange or pH lower than pH of K2SO4;

2


CAMBRIDGE INTERNATIONAL EXAMINATIONS Cambridge International General Certificate of Secondary Education MARK SCHEME for the October/November 2015 series

0620 CHEMISTRY

0620/51 Paper 5 (Practical), maximum raw mark 40

This mark scheme is published as an aid to teachers and candidates, to indicate the requirements of the examination. It shows the basis on which Examiners were instructed to award marks. It does not indicate the details of the discussions that took place at an Examiners’ meeting before marking began, which would have considered the acceptability of alternative answers. Mark schemes should be read in conjunction with the question paper and the Principal Examiner Report for Teachers. Cambridge will not enter into discussions about these mark schemes. Cambridge is publishing the mark schemes for the October/November 2015 series for most Cambridge IGCSE®, Cambridge International A and AS Level components and some Cambridge O Level components.

Page 2 Mark Scheme Syllabus Paper Cambridge IGCSE – October/November 2015 0620 51


Abbreviations used in the Mark Scheme • ; separates marking points • / separates alternatives within a marking point • () the word or phrase in brackets is not required but sets the context • A accept (a less than ideal answer which should be marked correct) • I ignore (mark as if this material were not present) • R reject • ecf credit a correct statement that follows a previous wrong response • ora or reverse argument • owtte or words to that effect (accept other ways of expressing the same idea)




1(d) time boxes correctly completed, ascending in magnitude; in seconds;

3 1

1(e) any two from: • effervescence / bubbles; • lighted splint pops; • temperature increased;

2

1(f) points correctly plotted: 4 correct = 2 3 correct = 1 2 or fewer correct = 0 smooth line graph;

2

1 1(g)(i) value from the graph quoted;

clearly shown on the graph; 1 1

1(g)(ii) value from the graph quoted; extrapolation shown clearly;

1 1

1(h) idea of fair test / comparability; 1 1(i)(i) exothermic / redox / displacement; 1 1(i)(ii) hydrogen; 1 1(i)(iii) values halved; 1

1(j) apparatus gas syringe / measuring cylinder over water / thermometer; measurements volume of gas / temperature of reaction; over time;

1

1 1




2(a) yellow / green; 1 2(b) white;

precipitate; 1 1

2(c) green precipitate; brown colour on sides / top of tube;

1 1

2(d) green precipitate; 1 2(e) (pink to) colourless;

brown; precipitate;

1 1 1

2(f) white precipitate; 1 2(g) brown precipitate;

bubbles; litmus paper turns blue / pH 10–12;

1 1 1

2(h) yellow; precipitate;

1 1

2(i) iron; (II); chloride;

1 1 1

2(j) silver / lead; nitrate;

1 1



0620 CHEMISTRY









1(d) time boxes correctly completed, ascending in magnitude; in seconds;

3 1

1(e) any two from: • effervescence / bubbles; • lighted splint pops; • temperature increased;

2

1(f) points correctly plotted: 4 correct = 2 3 correct = 1 2 or fewer correct = 0 smooth line graph;

2

1 1(g)(i) value from the graph quoted;

clearly shown on the graph; 1 1

1(g)(ii) value from the graph quoted; extrapolation shown clearly;

1 1

1(h) idea of fair test / comparability; 1 1(i)(i) exothermic / redox / displacement; 1 1(i)(ii) hydrogen; 1 1(i)(iii) values halved; 1

1(j) apparatus gas syringe / measuring cylinder over water / thermometer; measurements volume of gas / temperature of reaction; over time;

1

1 1




2(a) yellow / green; 1 2(b) white;

precipitate; 1 1

2(c) green precipitate; brown colour on sides / top of tube;

1 1

2(d) green precipitate; 1 2(e) (pink to) colourless;

brown; precipitate;

1 1 1

2(f) white precipitate; 1 2(g) brown precipitate;

bubbles; litmus paper turns blue / pH 10–12;

1 1 1

2(h) yellow; precipitate;

1 1

2(i) iron; (II); chloride;

1 1 1

2(j) silver / lead; nitrate;

1 1



0620 CHEMISTRY









1(a) initial and final volumes completed correctly; to 1 d.p.; comparable to Supervisor’s result (±0.3 cm3);

1 1 1

1(b) initial and final volumes completed correctly; to 1 d.p.; comparable to Supervisor’s result (±0.3 cm3);

1 1 1

1(c)(i) to remove M / residue / impurities / to clean it; 1 1(c)(ii) to remove water / so N is not diluted; 1 1(d)(i) colourless / pale green to pink; 1 1(d)(ii) there is already a colour change / self-indicating / it goes pink / owtte; 1 1(e)(i) Experiment 1 / solution M 1 1(e)(ii) volume for Experiment 1 is twice volume for Experiment 2 / volume for Experiment 2 is half volume for

Experiment 1; 1

1(e)(iii) solution N is twice as concentrated / strong ora; 2 1(f) half value from result in table for Experiment 2;

half volume (of L) used; 1 1

1(g) advantage: easy to use / quick / convenient; disadvantage: not accurate owtte;

1 1




2(a) white / colourless (solid / crystals); 2(b) any two from:

• melts / turns into a liquid; • condensation at top of tube; • solid turns brown; • gas (pH 4) formed;

2

2(c) pH 1–6 1 2(d) initial temperature recorded;

final temperature recorded, less than initial temperature; effervescence / fizz / bubbles;

1 1 1

2(e) blue solution; 1 2(f) effervescence / bubbles / heat produced;

lighted splint; pops;

1 1 1

2(g) white / grey / light blue (solid); 1 2(h) initial temperature;

final temperature higher than initial; turns blue;

1 1 1

2(i) blue; precipitate;

1 1

2(j) blue precipitate; dissolves / soluble / solution; deep / dark / royal blue (solution);

1 1 1

2(k) any two from: • hydrated / water; • acid; • organic;

2

2(l) copper (ions present); 1



0620 CHEMISTRY

0620/61 Paper 6 (Alternative to Practical), maximum raw mark 60





• ; separates marking points • / separates alternatives within a marking point • () the word or phrase in brackets is not required but sets the context • A accept (a less than ideal answer which should be marked correct) • I ignore (mark as if this material were not present) • R reject • ecf credit a correct statement that follows a previous wrong response • ora or reverse argument • owtte or words to that effect (accept other ways of expressing the same idea)




1(a) (teat) pipette; evaporating dish / basin;

1 1

1(b)(i) wire; (metal) with high melting point;

1 1

1(b)(ii) open; 1 1(c)(i) pH > 7 / purple / blue / dark green; 1 1(c)(ii) milky / white / white precipitate / cloudy; 1


2(a) straight line, drawn with a ruler, missing the point at n = 3; 1 2(b) 2 from:

• measuring / recording error / anomalous result; • equal amounts not burnt; • heat losses; • incomplete combustion;

2

2(c) reading from the graph / expected answer 4100 ± 50; indication of extrapolation from the graph;

1 1

2(d) for butane n = 4, ethane n = 2; value for ethane = 1550; butane = 2800 / about twice value or not exactly twice value;

1 1 1




3(a) electrolysis; 1 3(b) bulb lights / bubbles; 1 3(c) platinum; 1 3(d) glowing splint;

relights; 1 1

3(e) hydrogen (ions) positive / opposites attract 1 3(f) chlorine produced;

poisonous / toxic; 1 1


4(d) all time readings correctly recorded: 48, 68, 96, 132 4 correct = 3 3 correct = 2 2 correct = 1 0 or 1 correct = 0 in seconds;

3

1 4(e) all points correctly plotted: 48, 68, 96, 132

4 correct = 2 3 correct = 1 2 or fewer correct = 0 smooth line graph;

2

1 4(f)(i) value from the graph, 0.7;

shown clearly on the graph; 1 1




4(f)(ii) value from the graph, e.g. 34 s; extrapolation shown clearly;

1 1

4(g) idea of fair test / comparability; 1 4(h) 21 (°C);

49 (°C); 1 1

4(i)(i) exothermic / redox / displacement; 1 4(i)(ii) hydrogen; 1 4(i)(iii) values halved; 2

4(j) apparatus gas syringe / thermometer; measurements volume of gas / temperature of reaction; over time;

1

1 1


5(a) yellow / green; 1 5(b) white precipitate; 1 5(c) green;

precipitate; 1 1

5(d) green precipitate; 1 5(e) brown;

precipitate; 1 1

5(i) silver / lead; nitrate;

1 1




6 7 from: • weighed amount / x g of toothpaste; • add water; • stir / heat; • filter (to obtain calcium carbonate); • wash; • dry; • weigh residue; • calculate percentage calcium carbonate;

7



0620 CHEMISTRY










1(a) pipette; burette;

1 1

1(b) named indicator; 1 1(c) all volumes correct: 16.3, 16.9, 16.2, 16.1

4 correct = 2 3 correct = 1 2 or fewer correct = 0

2

1(d)(i) neutralisation / acid-base reaction / exothermic; 1 1(d)(ii) (indicator) changed colour; 1 1(e)(i) Experiment 2 / the second one / 16.9; 1 1(e)(ii) measuring or recording error /

overshot end-point / manual error with burette;

1

1(e)(iii) 16.2; cm3;

1 1

1(f) hydrochloric acid; less volume used than sodium hydroxide;

1 1




2(a) chromatography; 1 2(b) (teat) pipette / capillary tube; 1 2(c) water / organic solvent; 1 2(d) compound Q is insoluble; 1 2(e) between (4.7 and 5.1) divided by (6.2 or 6.3);

answer: between 0.74 and 0.82; 1 1


3(a) all temperatures correctly recorded: 23, 36, 47, 58, 70, 79

6 correct = 3 5 correct = 2 4 correct = 1 3 or fewer correct = 0

3

3(b) all points correctly plotted: 23, 36, 47, 58, 70, 79 6 correct = 2 5 correct = 1 4 correct = 0 smooth curve;

2

1 3(c) third point / at 47 °C or 99 s;

not on smooth line / curve; 1 1

3(d) 118; seconds / sec / s; indication on the graph;

1 1 1

3(e)(i) (it) increases / higher the temperature faster reaction; 1




3(e)(ii) particles have more energy / move faster; more (chance of / successful) collisions;

1 1

3(f)(i) slower reaction / longer time; smaller surface area;

1 1

3(f)(ii) sketch above the curve not touching the original at any point; 1 3(g) to prevent escape of / splash of acid;

to allow carbon dioxide / gas to escape; 1 1


4 tests on ethene bromine (water); turns colourless;

ammonia red litmus / pH paper; turns blue / pH > 7; oxygen glowing splint; relights;

1 1

1 1

1 1




5(c) copper; chloride;

1 1

5(d) colourless; 1 5(e)(i) white;

precipitate ; insoluble / no change / no reaction ;

1 1 1

5(e)(ii) no precipitate / slight white precipitate; no change / no reaction;

1 1

5(e)(iii) yellow; precipitate;

1 1




6 Method 1: Monitoring the reaction of the metal with acid 6 from:

• named acid; • same or stated volume of (same concentration of) acid; • fair test idea, i.e. same surface area / size / mass / amount metal; • measure volume of gas / count bubbles / temperature change / observe complete reaction; • suitable reference to time; • conclusion / comparison, e.g. most effervescence = most reactive;

Method 2: Displacement reaction 6 from:

• react each metal; • with named acid; • to prepare salt solution of each; • react each metal with each solution of salt; • observe if displacement occurs; • conclusion / comparison;

6



0620 CHEMISTRY










1(a) spatula; evaporating dish / basin;

1 1

1(b)(i) crush / powder / grind / pound zinc carbonate; add to acid and stir / mix; (until) no more bubbles / excess carbonate / solid remains;

1 1 1

1(b)(ii) filter / filtration etc.; 1 1(b)(iii) 2 from:

• evaporate; • until crystallisation point / crystals (start to) form / saturated; • leave to cool;

1


2(a) electroplating; 1 2(b) prevent rusting / corrosion / attractive appearance / shiny; 1 2(c) the negative / cathode; 1 2(d) M1 chromium (salt) / chromium + any named anion;

M2 nitrate / sulfate / chloride / ethanoate / suitable named anion; 1 1

2(e) coating will not stick / be even / dirt or grease will be trapped; 1 2(f) spoon not completely immersed in electrolyte / only half of spoon will be plated; 1




3(a) all temperatures correctly recorded: 30, 35, 33, 29 4 correct = 2 3 correct = 1 2 or fewer correct = 0 temperature rises: 5, 10, 8, 4;

2

1 3(b) idea of fair test / comparability of results / only one variable / control (variable); 1 3(c) 4 points plotted correctly, ± half a small square;

two intersecting straight lines drawn with a ruler; through points 1 and 2 and 3 and 4, extrapolated to intersect;

1 1 1

3(d)(i) 11 °C; 1 3(d)(ii) C = 28 and D = 22;

cm3; 1 1

3(e) 22 (°C) / 2 × value from (d)(i); 1




4(a) green; precipitate;

1 1

4(b) correct table of results for Experiment 1: final volumes, initial volumes and difference: 10.8 0.0 10.8; all readings in both tables to 1 decimal place;

1

1 4(c) correct table of results for Experiment 2: final volumes and initial volumes: 12.3 6.9;

difference correct: 5.4;

1

1 4(d)(i) to remove M / residue / impurities / to clean it; 1 4(d)(ii) to remove water / so N is not diluted; 1

4(e) there is already a colour change / self-indicating / it goes pink / owtte; M and N change colour or show when the reaction is complete;

1

1 4(f)(i) Experiment 2 / solution M / the first titration; 1 4(f)(ii) Experiment 2 uses 2 × volume of Experiment 3 ora; 1

4(f)(iii) twice as concentrated / strong ora; 2 4(g) half value from table result for Experiment 3 / 2.7;

half volume (of L) used; 1 1

4(h) advantage easy to use / quick / convenient; disadvantage not accurate owtte;

1 1




5(f) hydrogen / H2; 1 5(g) hydrated / water;

acid; 1 1

5(h) (grey / ) white (solid); 1 5(i) temperature increase / rise;

blue (solution); 1

5(j) blue; precipitate;

1 1

5(k) blue precipitate; dissolves / soluble / solution; deep / dark / royal blue (solution);

1 1 1




6 6 from:

• uses different (at least two) concentrations of sulfuric acid; • made by diluting with water; • same total volume of (diluted) sulfuric acid; • same mass / amount / size / length / surface area of magnesium (ribbon); • measure time (or run at the same time); • for magnesium to dissolve or react or disappear / y cm3 gas to collect / volume collected (set time) / bubbles

to stop / mass to decrease by x g / mass to stop decreasing; • compare times of reaction / results;

6

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0620 CHEMISTRY - maxpapers.commaxpapers.com/wp-content/uploads/2012/11/0620_w15_ms_all.pdf · 0620/11 Paper 1 (Multiple Choice), maximum raw mark 40 ... Page 2 Mark Scheme Syllabus