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CAMBRIDGE INTERNATIONAL EXAMINATIONS

Cambridge International General Certificate of Secondary Education

MARK SCHEME for the October/November 2014 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 2014 series for most Cambridge IGCSE

®, Cambridge International A and AS Level components and some

Cambridge O Level components.

Mark Scheme Syllabus Paper

Cambridge IGCSE – October/November 2014 0620 11

© Cambridge International Examinations 2014

Question Number

Key Question Number

Key

1 D 21 B

2 A 22 B

3 D 23 B

4 A 24 B

5 B 25 A

6 A 26 D

7 C 27 D

8 C 28 D

9 D 29 A

10 D 30 B

11 D 31 C

12 A 32 B

13 C 33 D

14 C 34 A

15 B 35 A

16 B 36 D

17 B 37 A

18 D 38 C

19 B 39 B

20 A 40 B





0620 CHEMISTRY








Question Number

Key Question Number

Key

1 D 21 B

2 D 22 B

3 A 23 B

4 A 24 D

5 A 25 A

6 C 26 B

7 C 27 A

8 B 28 D

9 D 29 D

10 D 30 C

11 A 31 B

12 D 32 B

13 C 33 A

14 C 34 A

15 B 35 D

16 B 36 A

17 D 37 D

18 B 38 B

19 B 39 C

20 A 40 B





0620 CHEMISTRY








Question Number

Key Question Number

Key

1 D 21 C

2 C 22 B

3 D 23 B

4 D 24 B

5 B 25 A

6 A 26 A

7 C 27 D

8 B 28 D

9 B 29 B

10 D 30 B

11 D 31 C

12 A 32 A

13 D 33 D

14 C 34 A

15 D 35 C

16 B 36 D

17 B 37 C

18 D 38 B

19 B 39 B

20 C 40 C





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 2014 series for most Cambridge IGCSE






1 (a) (i) E [1] (ii) A and D [1] (iii) D [1] (iv) B [1] (v) D [1] (vi) A and D [1] (b) C2H4Br2 [1] (c) 4 (H2O) [1] 5 (O2) [1] note: mark dependent on 4 (H2O) [Total: 9] 2 (a) (i) sodium / Na+ [1] (ii) X is fluoride [1] Y is nitrate [1] (iii) 0.244 (mg) [1] allow: 0.24 (iv) 4th box down ticked (weakly acidic) [1] (b) (add nitric acid) add silver nitrate [1] white precipitate [1] note: mark dependent on correct reagent (c) polymer [1] monomer [1] [Total: 9]




3 (a) ring around the OH group [1] (b) bromine (water) [1] allow: bromination decolourised / turns colourless [1] note: mark dependent on correct reagent ignore: goes clear / gets discoloured allow: potassium manganate(VII) / potassium permanganate (1) turns colourless (1) ignore: incorrect colour of reagent (c) (i) to break up the cells / to extract the pigment / to separate the pigment from

the petals / idea of getting the colour out of the petals, e.g. otherwise the colour won’t come out [1]

idea that solvent dissolves the pigment / idea of making a solution [1] ignore: find out how pure the rose petals are / reference to separating

colours (ii) pigment might be absorbed onto filter paper / pigment sticks to filter paper [1] (d) (i) chromatography [1] (ii) spot near the bottom and above the solvent level [1] (iii) to keep atmosphere in jar saturated (with solvent vapour) [1] allow: to reduce / prevent (solvent) evaporation (iv) A and C [1] (e) structure of ethanol with ALL atoms and bonds shown [2] [Total: 12]




4 (a) thermometer [1] (b) Any two from: [2]

• same volume of water in can

• same height of burner (from can)

• wick same height

• same rate / amount of stirring of water

• allow: same temperature of water at start

• allow: same amount of fuels burnt / same temperature rise

• allow: same type of can (c) so same temperature throughout the water / to stop differences in temperature in

the different parts of the water / otherwise the temperature will be higher at the bottom (of the water) / so not hotter in one place [1]

ignore: to mix the water / so there are no convection currents (d) decreases / goes down [1]

idea of liquid or fuel turning to vapour / gas; [1] allow: gases formed ignore: fuels evaporate note: 2nd mark dependent on first

(e) F [1] (f) (i) mixture of metals / mixture of metal(s) + non-metals [1] do not allow: compound (ii) covers surface / idea of protective layer [1]

prevents contact with air / prevents contact with water / so air (or water) does no react with steel [1] do not allow: reference to tin being more reactive / sacrificial protection (for second marking point)

(g) 1st box down ticked (giant covalent) [1] [Total: 11]




5 (a) Any four from: [4]

• suitable named metal / metal oxide e.g. reactive metal such as Mg / Zn or

• their oxides

• suitable named acid

• metal + acid gives metal salt / named metal gives named metal salt

• metal + acid gives off hydrogen note: complete word equation for metal + acid → salt + hydrogen (2)

• metal oxide + acid gives metal salt / named metal oxide gives named metal

• salt

• water also product of reaction of metal oxide + acid

note: complete word equation for metal oxide + acid → salt + water (2) (b) exothermic [1] (c) suitable use of radioactive isotope e.g. detecting leaks in pipes / checking

thickness of paper / tracer / cancer treatment / investigating thyroid function [1] ignore: atomic bombs / explosions (d) protons 92 and 92 [1] neutrons 143 and 146 [1] electrons 92 and 92 [1] [Total: 9] 6 (a) (i) (concentration) decreases [1] then remains constant [1] allow: levels out (ii) 3.8 (hr) / 3 hr 48 min [1] (iii) 9 (hr) [1] allow: 8.8–9.2 (hr) (iv) steeper graph line from same starting point [1] levels off lower than 0.10 mol /dm3 [1] (v) increase the temperature / increase concentration of sodium hydroxide [1] allow: add a catalyst




(b) Any four from: [4]

• acid in burette

• use (volumetric) pipette to put sodium hydroxide into flask

allow: sodium hydroxide in burette / acid in flask

• idea of correct setup of apparatus, i.e.flask under burette

• indicator in flask

• run hydrochloric acid into sodium hydroxide

• until indicator changes colour

• any indication of good technique e.g. repeating experiment / add acid • slowly / shaking flask after each addition of acid

note: answers must be in the correct context, e.g. do not allow indicator in burette

(c) bonding pair of electrons between H and Cl and no additional electrons on the H

atom [1] six non-bonding electrons around the chlorine atom [1] ignore: inner shell electrons in Cl. [Total: 13] 7 (a) for better crop / for better plant growth / to replace elements (or named elements

or minerals) lost from soil when crops harvested / for more plant protein [1] allow: to give more nutrients to plants ignore: for healthy plant growth / to give plants the compounds they need to grow

/ to help plants grow (b) neutralisation acid-base (reaction) [1] (c) ammonium nitrate [1] (d) 2 NH4

+ to 1 SO4

2– / 2 ammonium to 1 sulfate [1] allow: 2:1 or 1:2 ratio unqualified allow: (NH4)2SO4 (e) Any two from: [2]

• slaked lime can form an alkaline solution with water / slaked lime is calcium

• hydroxide / slaked lime is a hydroxide / slaked lime is basic

• slaked lime reacts with ammonium (salts) allow:: slaked lime reacts with fertiliser

• ammonia escapes from soil / gas escapes from soil




(f) positive: anode and negative cathode [1] at + electrode → chlorine [1] at – electrode → potassium [1] [Total: 9] 8 (a) Any four from: [4]

• dissolving

• diffusion

• in iodine solid the particles are close together

• in iodine solid the particles only vibrate ALLOW: particles do not move

• in solution the iodine molecules are further / far apart

• in solution the particles are randomly arranged/ no particular arrangement

• in solution, particles move (fairly) freely / in solution particles slide over solvent molecules

allow: in solution particles move slowly (from place to place)

• in solution there is bulk movement of particles from higher to lower concentration / particles spread out in solution / move everywhere / mix up

allow: particles move from higher to lower concentration

• ideas of explanation of dissolving in terms of solvent molecules getting between the iodine particles

• ideas about forces between particles of iodine being weakened on dissolving (b) (i) solid [1] (ii) heat causes astatine to melt / energy causes astatine to melt [1] allow:: the astatine has melted / radioactivity melts the astatine (iii) At2 on right [1] 2 (NaAt) on left [1] note: 2nd mark dependent on At2 or 2At on right [Total: 8]





0620 CHEMISTRY








1 (a) (i) A [1] (ii) B [1] (iii) C [1] (iv) E [1] (v) E [1] (vi) D [1] (b) 1 mark for each correct word: atoms; protons; neutrons. [3] [Total: 9] 2 (a) (i) chloride / Cl

– [1] (ii) sulfate [1] (iii) MgCl

2 [1] (iv) 26 g [1] (b) bromine water / bromine / aqueous bromine [1]

saturated → no colour change or remains orange / yellow / brown [1] note: mark dependent on correct reagent unsaturated → decolourised / goes colourless [1] ignore: goes clear / discoloured note: mark dependent on correct reagent allow: (acidified) potassium manganate(VII) (1) remains purple / remains pink / no colour change with saturated hydrocarbon (1) decolourised with unsaturated hydrocarbon (1)

(c) (i) pH 5 [1] (ii) one or both carboxylic acid groups ringed [1] [Total: 9] 3 (a) sulfuric acid + sodium chloride → sodium sulfate + hydrogen chloride [1]




(b) (i) bonding electron pairs on both overlap areas between hydrogen and oxygen atoms [1] do not allow: additional electrons on the hydrogen atom 4 non-bonding electrons on outer shell of oxygen [1] note: these electrons do not have to be paired up

(ii) white [1]

precipitate [1] (c) (i) 10.8 [1] (ii) 1.5 (cm3) [1] (iii) 13 (cm3) [1] (d) it loses oxygen / MnO2 loses oxygen / hydrogen gains oxygen [1]

allow: oxidation number of manganese decreases / manganese gains electrons (e) C

because: forms different ions / ions with different charges / forms 2 types of ions [1] note: dependent on C

has coloured oxide / has coloured compound [1] ignore: has high boiling point / has high density

[Total: 11] 4 (a) H2O on right [1]

2 (HCl ) on left [1] note: mark dependent on H2O on right

(b) (i) A = flask / Erlenmeyer [1]

B = (top pan) balance [1] (ii) carbon dioxide is a gas / gas escapes / carbon dioxide escapes / carbon

dioxide given off / gas given off [1] (c) (i) allow: 420–440 (s) [1] (ii) 0.175 g [1] (iii) increases / gets faster [1]

decreases / gets slower [1]




decreases / gets slower [1]

(d) 2nd and 3rd boxes down ticked (decomposition and endothermic) [2] (e) (i) Any two from: [2]

• calcium oxide is basic

• reacts with acidic gases / reacts with acidic vapours / reacts with sulfur dioxide / removes acidic gases / removes sulfur dioxide allow: reacts with acids

• idea of neutralisation ignore: prevents gases escaping unless qualified ignore: reacts with sulfur

(ii) any suitable use e.g. neutralising (or reducing acidity of) acidic

soils / neutralising (or reducing acidity of) acidic industrial waste / making mortar / steelmaking [1]

[Total: 15] 5 (a) Any four from: [4]

• both giant structures

• both have layered structures

• graphite covalent

• sodium chloride ionic

• graphite macromolecule / giant covalent structure

• graphite has layers which are separated / further apart (than C-C bonds)

• sodium chloride has ions touching

• graphite has only one type of particle / graphite is an element / only has C atoms

• sodium chloride has two types of particles / sodium chloride is a compound

• graphite has hexagonal arrangement (of atoms)

• sodium chloride has cubic arrangement allow: square arrangement

• graphite has atoms all of one size

• sodium chloride has different sized particles / ions ignore: properties / weak or strong bonding

(b) (i) substance containing only one type of atom [1]

allow: substance that cannot be split up (by chemical means) (ii) C + O2 → CO2 [2]




(c) (i) A [1] (ii) C [1] (iii) B [1] (iv) D [1] [Total: 11] 6 (a) (i) Any two from: [2]

• have same functional group

• group of similar compounds / have similar chemical properties

• (molecular) formula increases by CH2 unit

• physical properties show a trend / density shows a trend / boiling points show a trend

• they have a general formula (ii) C5H12 [1] (iii) increases [1] (iv) allow: between 0.50 and 0.58 [1] (b) any suitable solid fuel e.g. coal / wood / coke / peat [1]

ignore: bitumen / petroleum

any suitable liquid fuel e.g. paraffin / fuel oil / diesel / petrol etc. [1] (c) (i) X in top compartment; [1]

allow: X in top pipe F outside or in bottom right pipe; [1] M outside or in bottom left pipe; [1]

(ii) C2H4 [1]

H2 [1] (iii) high temperature [1]

allow: heat / stated temperatures between 200–1000 °C catalyst [1] ignore: names of incorrect catalysts

[Total: 14]




7 (a) Any four from: [4]

• melting / solid changes to liquid ignore: dissolving

• in solid gallium the particles are close together

• in solid gallium the particles only vibrate allow: particles do not move

• when gallium melts particles become random / move randomly

• when gallium melts, the particles start sliding over each other / bumping into each other / particles move ignore: particles further apart in liquid

• idea of energy (of the hot tea causing the particles to slide / move)

• ideas about forces between particles being weakened (on melting) note: there must be some reference to particles / atoms / ions to score these marking points

(b) 2 (Ga2O3) [1]

4 (Ga) [1] note: 2nd mark dependent on first being correct

(c) Any two from: [2]

• aluminium does not corrode / does not react;

• aluminium has an (unreactive) oxide layer

• low density / lightweight

• malleable

• allow: not toxic note: unreactive oxide layer is 2 marks ignore: does not rust

(d) (i) arrow under Al foil [1] (ii) Al2Cl6 [1]

ignore: AlCl3 (iii) aluminium has lower density (than silver) [1]

allow: aluminium is less expensive ignore: reference to melting point

[Total: 11]





0620 CHEMISTRY








1 (a) (i) B and D [2] (ii) A [1] (iii) C [1] (iv) A [1] (v) D [1] (b) KBr [1] allow: K+Br–

(c) 146 [2] allow: 1 mark for correct atomic masses 19 and 32 [Total: 9] 2 (a) Any four from: [4] solids: particles close together / no space between particles / particles arranged

regularly / particles touching solids: particles only vibrate allow: particles cannot move / particles in fixed positions liquids particles can slide over each other / particles have limited movement ignore: particles can move unqualified liquids: particles close together / particles not arranged regularly / particles

arranged randomly / particles not in fixed positions ignore: particles further apart than in solids gases: particles far apart / particles arranged randomly gases: particles can move everywhere / particles move anywhere / particles move

randomly note: It must be clear which state is being referred to note: there must be reference to particles (or atoms / molecules / ions) in the

answer to gain marks (b) (i) A [1] (ii) E and F [2] allow: B (iii) C and E [2] (iv) B and F [2]




(c) (i) 4th box down (last box) ticked [1] (ii) argon is unreactive / inert [1] air (or oxygen) may oxidise metals / air (or oxygen) may react with the (hot)

metals / to prevent the air (or oxygen) reacting with the metals [1] [Total: 14] 3 (a) (i) mortar [1] allow: mortar and pestle (ii) any suitable solvent other than water e.g. ethanol [1] allow: ethanoic acid / aqueous ammonia ignore: hydrochloric / sulfuric / nitric acids / strong alkalis / aqueous solutions

of salts (iii) evaporate some of the solvent [1] allow: evaporate / heat allow: add more rhubarb (b) (i) it would dissolve / it would mix with the solvent / solvent would wash it off / so

that the spot / Y didn’t dissolve in the solvent / Z would dissolve in the solvent [1] (ii) any two from: [2] dip paper into the solvent put lid on jar let solvent run up paper / let solvent separate spots ignore: wait for spots to appear / spots start to spread (unqualified) take paper out before solvent reaches the top / record solvent front ignore: reference to Rf values / locating agents (c) (i) ring around one or both carboxylic acid groups; [1] do not allow: ring around whole structure (ii) C2H2O4 [1] ignore: (COOH)2




(d) (i) H2O [1] (ii) CO and CO2 are gases / CO and CO2 are given off / the products are gases

(and water) [1] ignore: other substances evaporated (iii) any suitable source e.g. respiration / burning fuels / burning named carbon-

containing fuel / from limekilns or other suitable decomposition reaction [1] ignore: from burning (unqualified) / exhaled air / animals (unqualified) allow: from car exhausts (iv) any two of: [2] it is a greenhouse gas / absorbs infrared radiation allow: warms the atmosphere / traps heat in the atmosphere causes global warming / increase temperature of the atmosphere allow: warms the atmosphere / traps heat in the atmosphere reject: absorbs heat from the Sun effects of global warming e.g. desertification / rise in sea level / more extreme

weather / climate change ignore: references to ozone layer [Total: 13] 4 (a) filter funnel with filter paper + container to collect filtrate [1] correct labels for two of: (filter) funnel, filter paper, baker or flask [1] ignore: incorrect labels ignore: filtrate / water / sand (b) (i) potassium nitrate [1] (ii) Na+ and CO3

2– (both required) [1] (iii) sodium chloride [1] (iv) total mass = 20 g [1] % by mass = 14% [1] allow: error carried forward from incorrect total mass (c) (i) CO2 [1] (ii) pH 12 [1] [Total: 9]




5 (a) alcohol(s) / alkanol [1] (b) O–H [1] allow: OH (c) (i) 3 (H2) [1] (ii) (hydrogen is) flammable / explosive [1] allow: fire hazard (CO is) poisonous / toxic [1] ignore: CO harmful (d) (i) decreases [1] then remains constant [1] (ii) 0.28 (mol / dm3) [1] (iii) allow: values between 44–46 (hours) [1] (iv) curve steeper at start; [1] curve levels out at same level and before 45 hrs [1] (e) bonding pair of electrons between H and Cl [1] do not allow: if extra electrons on the H atom Six non-bonding electrons around the Cl [1]

ignore: inner shell electrons in Cl [Total: 13] 6 (a) (i) acidic oxide because oxide of non-metal [1] (ii) Any three from: [3] sulfur dioxide reacts with water in air / reacts with water on surface of

building / forms acid rain allow: sulfur dioxide is acidic / it is acidic limestone is a carbonate idea of reaction of acid with limestone / carbonate carbon dioxide (+ salt + water) formed




(b) (i) carry out in fume cupboard [1] (ii) speeds up reaction [1] (iii) O2 (on left) [1] correct balance (2 on right) [1] note: second mark dependent on O2 or 2O on left (iv) to prevent it turning into liquid / vapour [1] allow: so temperature is below melting point / so that it can form crystals (v) 200 g [1] (c) (i) 4th box down ticked (pipette) [1] (ii) indication that indicator changes colour [1] allow: any stated colour change (d) water absorbed [1] [Total: 13] 7 (a) Any four from: [4] colour gets darker down the Group correct colours of two of the halogens (chlorine green / yellow green + bromine

brown / reddish-brown + iodine grey / grey-black / black) note: all three halogen colours correct is 2 marks correct state of two of the halogens (chlorine gas, bromine liquid, iodine solid) note: all three states correct is 2 marks reactivity decreases down the Group allow: any two differences in reactivity correctly compared e.g. chlorine is more

reactive than bromine (1 mark maximum) do not allow: mention of incorrect difference in reactivity example of reactivity of pair of halogens / halides e.g. chlorine reacts with

potassium bromide allow: density increases down Group allow: boiling points / melting points get higher down the Group (b) diatomic [1] (c) 7 electrons in the outer shell [1] 2 electrons in inner shell [1] note: this mark cannot be obtained if other inner shells are drawn (d) bromine + potassium iodide → iodine + potassium bromide [2] [Total: 9]





0620 CHEMISTRY

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







1 (a) Match the following pH values to the solutions given below. 1 3 7 10 13 The solutions all have the same concentration. solution pH aqueous ammonia, weak base 10 dilute hydrochloric acid, a strong acid 1 aqueous sodium hydroxide, a strong base 13 aqueous sodium chloride, a salt 7 dilute ethanoic acid, a weak acid 3 [5] (b) Hydrochloric acid strong acid or ethanoic acid weak acid [1] OR: hydrochloric acid completely ionised or ethanoic acid partially ionised hydrochloric acid greater concentration of/more H+ ions (than ethanoic acid) [1] (c) Rate of reaction with Ca, Mg, Zn, Fe [1] Strong (hydrochloric) acid bubbles faster or more bubbles or dissolves faster [1] OR: rate of reaction with (metal) carbonate [1] strong (hydrochloric) acid faster or more bubbles or dissolves faster (only if

carbonate insoluble) [1] OR: electrical conductivity [1] strong (hydrochloric) acid better conductor [1] [Total: 9] 2 (a) soft because weak forces between layers/sheets/rows [1] layers can slip/slide [1] good conductor because electrons can move/mobile [1] (b) it is soft: pencils or lubricant or polish [1] good conductor: electrodes or brushes (in electric motors) [1] (c) (i) every silicon atom is bonded/attached to 4 oxygen atoms or every oxygen

bonded/attached to two silicon atoms [1] (ii) Any two from: high melting point/boiling point hard colourless crystals/shiny poor/non-conductor of electricity/insulator insoluble in water [2] [Total: 8]




3 (a) Any two from: bleach/making wood pulp/making paper food/fruit juice/wine preservative fumigant/sterilising/insecticide [2] (b) heating/roasting/burning (zinc sulfides) [1] in air/oxygen COND on M1 [1] (c) (i) V2O5 [1] (ii) position of equilibrium shifts right/yield increases [1] to save energy [1] (iii) faster reaction/rate [1] more collisions per second/higher collision frequency [1] fewer moles/molecules (of gas) on right [1] (so) position of equilibrium shifts right/yield increases [1] (d) (the reaction is) too violent/too exothermic or produces mist/fumes (of acid) [1] [Total: 12] 4 (a) (i) insufficient/limited oxygen [1] or 2C + O2 → 2CO coke/carbon reacts with carbon dioxide [1] or C + CO2 → 2CO (ii) Fe2O3 + 3CO → 2Fe + 3CO2 species (1) balancing (1) [2] (b) (i) carbon dioxide [1] (ii) CaO + SiO2 → CaSiO3 [2] [1] each side correct (iii) (molten) iron higher density (than slag) [2] (iv) No oxygen in contact with iron or layer of slag prevents hot iron reacting with

oxygen/air or (all) oxygen reacts with carbon (so no oxygen left to react with iron) [1]

(c) (i) air/oxygen and water (need both) [1]




(ii) aluminium oxide layer is impervious or non-porous or passive or unreactive or will not allow water/air to pass through it (rust allows passage of water or air or it flakes off) [1]

(d) (i) zinc more reactive (than iron/steel) [1] loses electrons [1] electrons move (from zinc) to iron [1] Zinc reacts (with air and water) or zinc corrodes or zinc is oxidised or zinc is

anodic or zinc forms positive ions or zinc forms Zn2+ or iron and steel don’t react with air/water or iron and steel are not oxidised or iron and steel do not form ions or iron and steel do not lose electrons or iron and steel are cathodic [1]

(ii) R to L in wire [1] (iii) 2H+ + 2e– → H2 species (1) balancing (1) [Total: 19] 5 (a) nitrogen and oxygen react [1] at high temperatures (in engine) [1] (b) M1 carbon monoxide (converted to) carbon dioxide or 2CO + O2 → 2CO2 [1] M2 (by) oxides of nitrogen (which are reduced to) nitrogen or 2NO → N2 + O2 or 2NO2 → N2 + 2O2 [1] M3 hydrocarbons (burn) making water [1] M4 products: any two from: carbon dioxide, water, nitrogen [1] (c) lead compounds are toxic or brain damage or reduce IQ or nausea or kidney

failure or anaemia [1] [Total: 7] 6 (a) (i) butanoic acid [1] methanol [1] (ii) number of moles of ethanoic acid = 0.1 [1] number of moles of ethanol = 0.12(0) [1] the limiting reagent is ethanoic acid [1] number of moles of ethyl ethanoate formed = 0.1 [1] maximum yield of ethyl ethanoate is 8.8 g [1]




(b) correct ester linkage [1] two ester linkages (COND on M1) [1] continuation (COND on M2) [1] (c) (i) add bromine water/bromine [1] turns colourless [1] remains brown/orange/reddish brown/yellow [1] ALLOW: potassium manganate(VII) (acidic or alkaline) [1] correct colour colourless/green or brown ppt [1] stays pink/purple [1] (ii) ester 1 [1] COND alkyl group is CnH2n+1 which is NOT C17H33 or C17H35 is CnH2n+1 or less hydrogen [1] (iii) soap or (sodium) salt (of a carboxylic acid) or carboxylate [1] alcohol [1] [Total: 17] 7 (a) (i) 6Li + N2 = 2Li3N species (1) balancing (1) (ii) N3– ion drawn correctly [1]

Charges correct (minimum 1 × Li ion and 1 nitride ion) [1]

(b) (i) 3 × shared pairs between N and 3 × F [1] only 2 non-bonding electrons on N, 6 non-bonding electrons on each F

(COND on first point) [1]

(ii) Strong attractive forces/strong ionic bonds in lithium nitride [1] weak (attractive) forces between molecules in NF3 [1] [Total: 8]





0620 CHEMISTRY








1 (a) foodstuffs or drugs [1] (b) (i) simple distillation fractional distillation or diffusion fractional distillation filtration or evaporation chromatography [5] (ii) M1 dissolving M2 filtration M3 evaporation or heat (to crystallisation point) M4 crystallisation or allow leave to cool [4] or M3 crystallisation M4 filtration OR: Adding to H2SO4 method M1 Add excess mixture to acid (or until no more dissolves) M2 Filtration or M1 Add excess acid to mixture M2 With heat M3 evaporation or heat (to crystallisation point) Stop marking if heated to dryness. M4 crystallisation or allow leave to cool or M3 crystallisation M4 filtration [Total: 10]

2 (a) Al3+ + 3e– → Al [2]

species (1) balancing (1)

(b) (i) AlCl3 + 3Na → 3NaCl + Al [2] species (1) balancing (1) (ii) M1 electrolysis [1] M2 molten sodium chloride [1] or M1 Add named more reactive metal (e.g. K) M2 Molten sodium chloride (c) (i) bauxite [1] (ii) M1 aluminium oxide / amphoteric oxide dissolves OR iron(III) oxide / basic oxide does

not [1] M2 Filter COND on M1 [1]




(iii) Any two from: Lowers (working) temperature or lowers mpt (of mixture) increases conductivity reduces cost OR energy need [2] (iv) M1 = Any one correct equation. M2 Oxygen mark Oxygen comes from oxide ions

or 2O2– � O2 + 4e M3 Carbon dioxide mark Anode reacts with oxygen / burns to form CO2 or C + O2 � CO2 M4 Carbon monoxide mark Anode reacts with limited oxygen / incompletely burns to form carbon monoxide

or 2C + O2 � 2CO or CO2 reacts with the anode to form carbon monoxide

or CO2 + C � 2CO M5 Fluorine mark Fluorine comes from cryolite or fluoride ions

or 2F– � F2 + 2e– [5] (d) (i) Has an impervious or non-porous or passive or unreactive or protective oxide layer [1] (ii) Any two from: good conductor of heat high melting point Unreactive towards foods [2] 3 (a) (i) C4H8 only CH2 (Allow C1H2) [2] (ii) Any unambiguous structural formula of methyl cyclopropane or but-1-ene or but-2-ene or

methyl propene [1] (iii) M1 same molecular formula [1] M2 different structural formulae or different structures or different arrangement of atoms [1] (iv) If ‘No’: one an alkane, the other an alkene or one is saturated / has single bonds, the other is unsaturated / has a double bond ignore: references to the ‘functional group’ If ‘yes’ both alkanes or both saturated ignore: references to the ‘functional group’ [1]




(b) (i) M1 Action of heat or catalyst or thermal decomposition (on an alkane) [1] Ignore steam. Ignore pressure. M2 Long-chained molecules or alkanes form smaller molecules (not smaller fraction) or

forms smaller alkenes (or alkanes) [1] (ii) C10H22 [1] (c) (i) M1 Correct structure of one repeat unit [1] M2 Continuation bonds COND on M1 [1] M3 use of brackets and subscript ‘n’ COND on M1 and M2 [1] (ii) dibromoethane or 1,2-dibromoethane [1] 4 (a) M1 brass [1] M2 copper COND on M1 [1]

(b) (i) 2ZnS + 3O2 � 2ZnO + 2SO2 [2] species (1) balancing (1) (ii) Manufacture of sulfuric acid or bleach or making wood pulp or making paper or food or fruit juice or wine preservative or fumigant or sterilising [1] (c) (i) sulfuric acid [1]




4 (c) (ii) Zn2+ + 2e � Zn [1] oxygen or water Allow O2 and H2O if no name seen [1] sulfuric acid [1] Allow: H2SO4 if no name seen 4 (d) (i) from zinc to carbon (clockwise direction on or near the wire) [1] (ii) to allow ions to flow [1] (iii) oxidation and loss of electron(s) or increase in oxidation number/state [1] reduction and decrease in oxidation number/state or gain of electron(s) [1] [Total: 13] 5 (a) (i) M1 Contain carbon, hydrogen and oxygen (only) [1] M2 hydrogen and oxygen is in a 2:1 ratio (or in the same ratio as water) [1] (ii) M1 -O- linkage [1] M2 3 monomer units with 3 blocks and 3 Oxygen atoms Cond [1] 5 (b) catalyst [1] biological or protein [1] 5 (c) (i) C A B [2] ABC = 1 ACB = 1 BCA = 1 CBA = 1 BAC = 0 Allow 70 for C, 40 for B and 20 for A (ii) M1 Energy mark: at higher temperature particles/molecules more have more energy or

move faster [1] M2 Collision frequency mark: collide more frequently/often or more collisions per unit

time or higher rate of collisions. [1] Ignore: ‘more collisions’ M3 Collision energy mark: more molecules have enough energy to react or more

collisions are above activation energy or successful [1]




(iii) C rate zero or enzymes denatured [1] [Total: 12] 6 (a) making fertilisers or pickling metals or making fibres or making phosphoric acid/phosphates

making dyes or making paints/pigments/dyes or making paper making plastics or making detergents or tanning leather or battery acid. [1]

(b) (i) add water (to yellow solid or to (anhydrous) iron(II) sulfate or to FeSO4 or to products [1] goes green [1] (ii) M1 Sulfur trioxide reacts with water to make sulfuric acid or equation [1] M2 sulfur dioxide reacts with oxygen to form sulfur trioxide or equation [1] (iii) M1 = 2.07 Allow 2.1 or 2.0666…7 M2 = 62.8.g M3 =( M2/152 =) 0.41(3)

M4 (=M1/M3) rounded to the nearest whole number × = 5 [4] 6 (c) (i) nitric acid or nitric(V) acid or HNO3 [1]

(ii) 2KNO3 = 2KNO2 + O2 [2] Species (1) Balance (1) [Total: 12]





0620 CHEMISTRY








1 (a) Bromine Physical: reddish-brown liquid or brown liquid or volatile liquid/low boiling point

liquid or poor/non-conductor (of electricity) or soluble in water or soluble in organic/non-polar solvents [1]

Chemical: Reacts with water or reacts with iodides (in solution) or displaces

iodine or reacts with alkenes/named alkene/unsaturated hydrocarbons or reacts with alkane in UV/named alkane in UV or valency/oxidation state(–)1 or forms Br– or gains or shares 1 electron or combines or reacts with metals/named metal or combines or reacts with non-metals/named non-metal or oxidising agent or bleaches litmus paper/indicator paper or corrosive or forms acidic oxides [1]

(b) Graphite Physical: (good) conductor (of electricity) or soft or lubricant or high melting

point/high boiling point or grey black or black solid or slippery or greasy (to touch) or brittle/breaks when subjected to stress or insoluble in water [1]

Chemical: reducing agent or reduces metal oxides/named metal oxide or reacts

with/burns in air/oxygen or forms an acidic oxide (CO2) or valency/oxidation state of 2 or 4 [1]

(c) Manganese Physical: (good) conductor (of heat/electricity) or high melting point/high boiling

point or forms coloured compounds/coloured ions or hard or strong or high density or malleable or ductile or sonorous or shiny [1]

Chemical: Variable or different valency/oxidation state/oxidation number or

catalytic activity or forms coloured compounds/coloured ions or forms complex ions/complexes or reacts with acids or reducing agent or reacts with non-metals [1]

[Total: 6]

2 (a) (i) (X(s) ↔) X(l) [1] (ii) melting point/freezing point (of X) [1] (iii) gas/gaseous or vapour [1] (iv) not horizontal or line slopes or line is lower [1]




(b) (i) 14.3 [1]

(ii) 85.7 ÷ 12 and 14.3 ÷ 1 or 7.14 and 14.3 [1] ratio 1:2 [1] CH2 [1] note: Award all 3 marks for correct answer allow: alternative working e.g.

85.7 × 84 ÷ 100 and 14.3 × 84 ÷ 100 or 71.988/72 and 12/12.012 [1] 6:12 or ratio 1:2 [1] CH2 [1] (iii) C6H12 [1] [Total: 9] 3 (a) (i) 3 [1] (ii) 70 [1] (b) Add octane (or other liquid hydrocarbon) (to soot) [1] COND(on addition of any solvent) filter (to remove insoluble forms of carbon) [1] (allow to) evaporate or heat or warm or leave in sun(to get crystals of fullerene) [1] (c) (i) graphite [1] (ii) delocalised electrons/free electrons/sea of electrons [1] COND (on electrons) move/mobile/electrons flow [1] (iii) Any two from: [2] potassium oxide potassium hydroxide potassium carbonate potassium hydrogencarbonate (bicarbonate) [Total: 10] 4 (a) carbon dioxide/CO2 [1] (b) 2H2 + O2 → 2H2O [1] (c) (i) anode/negative electrode and electrons lost(by hydrogen/H/H2)/electrons

move from this electrode [1] (ii) H2 → 2H+ + 2e(–) / H2 – 2e(–) → 2H+ / H2 + 2OH– → 2H2O + 2e(–) / H2 + 2OH– – 2e(–) → 2H2O [2] Species (1) Balancing (1)




(d) Any two from: CELL: lightweight quieter fewer working parts/less maintenance more efficient or less energy wasted or more energy

produced SUSTAINABILITY: conserves a limited resource/petroleum/fossil fuels unlimited supplies of renewable resource(of hydrogen

from water) POLLUTION: No or less greenhouse effect No or less acid rain No or less toxic gases No or less smog POLLUTANTS: No or less C/soot No or less CO2 No or less CO No or less SO2 No or less oxides of nitrogen/NO/NO2/N2O4/NOx No or less (unburnt) hydrocarbons No or less low level ozone H2O is the only product [2] [Total: 7] 5 (a) (i) rate decreases [1] concentration of sodium chlorate ((I))/reactant decreases [1] (ii) (initial) gradient greater/steeper (must start at origin) [1] same final volume of oxygen [1] (iii) (to prevent)photochemical reaction/(to prevent)reaction catalysed by

light/light breaks down or decomposes sodium chlorate((I)) [1] (iv) particles have more energy/particles move faster/ [1] more collisions [1] collisions more frequent or more often/greater chance of collision/collision

rate increases/more particles have energy to react/more collisions are successful or effective [1]

(b) (i) 2Cl

– → Cl2 + 2e(–) / 2Cl– – 2e(–) → Cl2 [1]

2H+ + 2e(–) → H2 / 2H+ → H2 – 2e(–) [1] hydrogen formed at cathode/– and chlorine at anode/+ [1] Na+ and OH– or sodium ions and hydroxide ions left in solution/form/become

sodium hydroxide [1] (ii) Cl2 + 2NaOH → NaClO/NaOCl + NaCl + H2O [2] Species (1) Balancing (1) [Total: 14]




6 (a) Rb loses 1 electron/1 electron in outer shell/1 valency or valence electron [1] Sr loses 2 electrons/2 electrons in outer shell/2 valency or valence electrons [1] (b) (i) (mix solutions of) rubidium carbonate/Rb2CO3 [1]

strontium chloride/SrCl2 or strontium nitrate/Sr(NO3)2 or strontium

sulfate/SrSO4 or strontium hydroxide/Sr(OH)2 [1] COND (on two correct reactants) filter or centrifuge or decant (the residue) [1] wash with water and dry/press between filter paper/put in (low) oven/put on a

(sunny) windowsill/put in sun/heat [1] (ii) SrCO3 → SrO + CO2 [1] (c) (i) rubidium nitrite or nitrate(III) [1] (ii) 2Sr(NO3)2 → 2SrO + 4NO2 + O2 [2] Species (1) Balancing (1) [Total: 10] 7 (a) (i) butanoic acid/butyric acid [1] displayed formula below [2]

(ii) any three from: same or similar chemical properties (same) general (molecular) formula (consecutive members) differ by CH2 same functional group common methods of preparation physical properties vary in predictable manner/show trends/gradually change or example of a physical property variation i.e. melting point/boiling

point/volatility [3] (iii) dissociates/ionises/splits up (into ions) [1] partially/incompletely/slightly/not fully [1] (donates) protons/(forms) H+/H3O

+(as the only positive ion) [1]

(1) (1)




(b) (i) methyl propanoate [1] CH3CH2COOCH3/CH3CH2CO2CH3/C2H5COOCH3/C2H5CO2CH3 [1] (ii) methyl ethanoate [1]

(c) (i) 3C4H10 + 5 ½ O2 → 4C2H5COOH + 3 H2O [1] (ii) propanol or propan-1-ol or propanal [1] [Total: 14] 8 (a) (changes from) blue (1) to pink (1) [2] (b) no more (solid) dissolves or no more cobalt(II) carbonate dissolves or no more effervescence or bubbling or fizzing [1] filter(residue)/centrifuge/decant [1] evaporate/heat/warm/boil/leave in sun AND until most of the water has

gone/some water is left/until it is concentrated/saturation (point)/crystallisation point/crystals form on glass rod or microscope slide/crystals start to form [1]

Leave/allow to cool/allow to crystallise/filter (off crystals)/wash(with distilled

water)/dry crystals with filter paper/dry crystals in warm place or dry in oven or dry on windowsill [1]

(c) number of moles of HCl in 50 cm3 of acid, concentration 2.2 mol/dm3 = 0.11 [1] maximum number of moles of CoCl2.6H2O which could be formed = 0.055 [1] mass of 1 mole of CoCl2.6H2O = 238 g maximum yield of CoCl2.6H2O = 13.09 g [1]

percentage yield = 48.2% or ecf mass of CoCl2.6H2O above/13.09 × 100% to 1 dp [1]

[Total: 10]





0620 CHEMISTRY

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







1 (a) Table of results for Experiment 1

initial and final volumes and difference completed correctly (1)

to 1 decimal place (1)

comparable to supervisors (1) ±2 cm3 [3]

(b) Table of results for Experiment 2

Initial and final volumes completed correctly (1)

and difference (1)


(c) (i) yellow, not orange to pink / orange (1) not red [1]

(ii) as an indicator / to show end point (1)

ignore to see colour change [1]

(iii) neutralisation (1) [1]

(d) (i) experiment 1 (1) [1]

allow: ecf from tables

(ii) quantitative comparison

experiment 1 4X volume experiment 2/x cm3 more than (1) [1]

(iii) solution B more concentrated/stronger (1) or converse

explanation e.g. 4X as concentrated/less volume used (1) [2]

(e) half value / half value from table result for experiment 2 (1) cm3 (1) [2]

(f) advantage

easy to use / quick / convenient (1)

disadvantage

not accurate (1) [2]

(g) same volume of each solution (1) add suitable named reactant (1)

expected observation (1) comparison (1)

e.g. 10 cm3 of each acid (1) add strip of magnesium/named carbonate (1)

effervescence (1) more rapid bubbles means stronger acid (1) [4]




2 (a) (i) purple / black / violet (1) crystals (1) [2]

(ii) drops / condensation at top of tube (1) colour change to green/grey (1)

green on cooling (1) max [2]

(b) (i) green / grey (1) not white

precipitate (1) [2]

dissolves / clears (1) [1]

(ii) green / grey not white precipitate (1) insoluble (1) [2]

(c) blue / green (1) glowing splint (1) relights / glows brighter (1)

effervescence / bubbles (1) max [3]

(d) no reaction / no precipitate / no change / colourless solution (1) [1]

(e) white (1) precipitate (1) [2]

(f) hydrated/water (1)

allow transition metal [1]

(g) not halide / chloride / iodide (1) sulfate (1)

transition metal / iron / chromium / catalyst (1) [3]





0620 CHEMISTRY








1 (a) Table of results for Experiment 1

initial and final volumes and difference completed correctly (1)

to 1 decimal place (1)


(b) Table of results for Experiment 2

Initial and final volumes completed correctly (1)

and difference (1)


(c) (i) yellow, not orange to pink / orange (1) not red [1]

(ii) as an indicator / to show end point (1)

ignore to see colour change [1]

(iii) neutralisation (1) [1]

(d) (i) experiment 1 (1) [1]

allow: ecf from tables

(ii) quantitative comparison

experiment 1 4X volume experiment 2/x cm3 more than (1) [1]

(iii) solution B more concentrated/stronger (1) or converse

explanation e.g. 4X as concentrated/less volume used (1) [2]

(e) half value / half value from table result for experiment 2 (1) cm3 (1) [2]

(f) advantage

easy to use / quick / convenient (1)

disadvantage

not accurate (1) [2]

(g) same volume of each solution (1) add suitable named reactant (1)

expected observation (1) comparison (1)

e.g. 10 cm3 of each acid (1) add strip of magnesium/named carbonate (1)

effervescence (1) more rapid bubbles means stronger acid (1) [4]




2 (a) (i) purple / black / violet (1) crystals (1) [2]

(ii) drops / condensation at top of tube (1) colour change to green/grey (1)

green on cooling (1) max [2]

(b) (i) green / grey (1) not white

precipitate (1) [2]

dissolves / clears (1) [1]

(ii) green / grey not white precipitate (1) insoluble (1) [2]

(c) blue / green (1) glowing splint (1) relights / glows brighter (1)

effervescence / bubbles (1) max [3]

(d) no reaction / no precipitate / no change / colourless solution (1) [1]

(e) white (1) precipitate (1) [2]

(f) hydrated/water (1)

allow transition metal [1]

(g) not halide / chloride / iodide (1) sulfate (1)

transition metal / iron / chromium / catalyst (1) [3]





0620 CHEMISTRY








1 (d) table of results

initial temperature boxes completed correctly (1)

final temperature boxes correctly completed (1)

differences correct (1) include minus signs

comparable to supervisors (1) [4]

(e) bubbles / fizzing / effervescence (1)

blue precipitate (1) [2]

(f) all bars at correct levels (2),

suitable scale (1)

labels (1) [4]

(g) (i) experiment 2 (1) [1]

(ii) experiments 2 and 3 (1) temperature decreased (1) [2]

(h) (i) half temperature change / half value in table (1) [1]

(ii) half temperature change / half value in table (1) [1]

(iii) half amount of solid used (1) [1]

(i) room temperature / value from table (1)

finished dissolving / reacting (1) [2]

(j) carbonate (1) carbon dioxide (1) acid (1)

Cu2+

(1) max [2]




2 tests on solution M (a) colourless see test (e) ignore clear

pH 1–3 (1) [1]

(b) bubbles (1) lighted splint goes out (1) [2]

(c) fizz / bubbles etc. (1)

lighted splint (1) pops (1) [3]

(d) white (1) precipitate (1) [2]

(e) appearance colourless (1) must have (a) correct as well [1]

pH 11–14 (1) [1]

(f) colourless / no change (1)

with excess white (1) precipitate (1) [3]

(g) litmus paper turns blue (1) pungent smell (1) [2]

do not allow: strong

(h) (i) hydrogen (1) [1]

(ii) ammonia (1) [1]

(i) hydrochloric acid (2) [2]

note: acid / chloride only (1)

(j) (sodium / potassium) hydroxide (1) [1]





0620 CHEMISTRY

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

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 2014 series for most Cambridge IGCSE




Cambridge IGCSE – October / November 2014 0620 61


1 (a) boxes completed to show stirrer / glass rod (1)

watchglass / evaporating dish (1) [2]

(b) to speed up the reaction (1) [1]

(c) correct answer 4.2 g (2)

if incorrect, evidence of 17.8 – 13.6 (1) [2]

(d) (i) solid / lead oxide visible / remaining (1) [1] do not allow: mention of precipitate

(ii) filtration (1) [1]

(iii) excess (1) [1]

allow: residue

(e) Any two from:

evaporation / steam (1)

solid / crystals formed (1)

breakdown / decomposition of solid (1) [2]

2 (a) smooth curve missing anomalous point (1) [1]

(b) composition of mixture double volume / 100 cm

3 of hydrogen peroxide (1)

more than 1 g of manganese(IV) oxide / powdered (1) [2]

ignore: references to water

note: double the concentration is valid for (2)

explanation double volume of gas (1)

faster reaction (1) [2]

(c) catalyst / increase the rate of the reaction (1) [1]

(d) sketch graph less steep than original for Experiment 1 (1)

to same level (1) [2]

3 (a) (i) chromatography (1) [1]

(ii) to prevent loss / evaporation of solvent (1) [1]

(b) when the solvent is near the top of the paper / before the solvent reaches the top of the

paper (1) [1]




(c) (i) 4 (1) [1]

(ii) yes, one artificial dye (1)

at same height / matches (1) [2]

4 (a) table of results for Experiment 1

initial volume completed correctly (1)

0 or 24.4

all readings to 1 decimal place (1) [2]

(b) table of results for Experiment 2

final volume completed correctly (1)

6.1

difference correct (1) [2]

(c) (i) neutralisation (1) [1]

allow: acid-base

(ii) as an indicator / to show end point (1) [1]

(d) water to remove the solution A of acid (1)

acid B to remove traces of water (1) [2]

(e) (i) Experiment 1

ecf from readings (1) [1]

(ii) any correct comparison (1) [1]

(iii) solution B more concentrated / stronger (1) or converse

less volume was needed (1) [2]

(f) half value from table result for experiment 2 (1)

cm3 (1) [2]

(g) advantage: easy to use / quick / convenient (1)

disadvantage: not accurate owtte (1) [2]

(h) same volume of each solution (1)

add suitable reactant (1)

expected observation (1)

comparison (1) [4]

note: e.g. 10 cm3 of each acid (1), add strip of magnesium / named carbonate (1)

effervescence (1), more rapid bubbles means stronger acid (1)




5 (c) no reaction / no change / no precipitate (1) [1]

(d) white (1)

precipitate (1) [2]

(e) transition metal present (1)

allow: iron

water / hydrated (1) [2]

(f) hydrated (1) iron (1) (II) (1) (sulfate) [3]

6 (a) (i) gas syringe / inverted measuring cylinder in trough of water (1)

labelled (1) [2]

(ii) limewater (1)

milky (1) [2]

(b) measured volume of water (1)

in named weighed container (1)

evaporate to dryness (1)

reweigh / measure mass of solid (1)

conclusion: e.g. double the mass of residue if 500 cm3 water used to check mass in

1000 cm3 (1) max [4]





0620 CHEMISTRY








1 (a) (i) U-tube (1)

gas jar (1) [2]

not: measuring cylinder

(ii) arrow inserted under shaded solid mixture (1) [1]

(b) less dense / lighter than air (1)

reacts / dissolves in water (1) [2]

(c) reaction occurs (1)

ammonia is alkaline / neutralisation / hydrogen chloride (1)

ammonium chloride formed (1) [3]

note: correct equation scores (3)

(d) red litmus (1)

turns blue (1) [2]

allow: pH / Universal Indicator (1)

turns blue / purple (1)

2 a solution of chlorine in water named indicator (1)

bleaches / turns white (1) [2]

do not allow: halide test

sulfuric acid named indicator (1)

result (1)

or add barium nitrate (1)

white precipitate (1)

or carbonate (1)

fizzes (1) [2]

allow: other valid alternatives

hexene bromine (water) (1)

decolourises (1) [2]

allow: lighted splint (1)

ignites (1)

limewater pass carbon dioxide (1)

milky / cloudy (1) [2]

allow: named indicator (1)

correct result (1)




3 (a) spatula (1) [1]

do not allow: spoon

(b) (i) sulfuric (1) [1]

(ii) reacts quickly at room temperature (1) [1]

allow: heat not needed / reacts anyway

(c) (i) sulfuric acid / the acid (1) [1]

(ii) solution will be acidic / not neutral / impure salt (1) [1]

(d) (i) crystals appear / description of using glass rod (1) [1]

not: precipitate / evaporate to dryness

(ii) lose water / dehydrate (1) [1]

allow: reference to anhydrous

ignore: break down of crystals / powder forms

4 (a) Table of results

temperature boxes completed correctly (3)

all 7 correct (3)

6 correct (2)

5 correct (1)

4 or fewer correct (0)

26 35 45 54 56 52 48 [3]

(b) all points correctly plotted (3)

all 7 correct (3)

6 correct (2)

5 correct (1)


two intersecting straight line graphs drawn with a ruler (1) [4]

(c) (i) value from graph, 50 (°C) (1) ± 1

shown clearly (1) [2]

(ii) value from graph, 34 ± 1 (1)

unit cm3 (1)

shown clearly (1) [3]

note: if tie-line not to peak of graph, max 1, for unit.

(d) sodium hydroxide (1)

less volume used than acid / volume of acid used was greater (1) [2]




(e) exothermic (1) [1]

(f) room / initial temperature / 26 °C (1)

ignore: 20 °C

reaction finished owtte (1) [2]

(g) repeat (1)

compare results (1) [2]

allow: take mean / average (1)

ignore: references to insulation

5 tests on solution A

(a) yellow / brown / orange (1) [1]

allow: combination of above colours

do not allow: red, but allow: red-brown

(b) (orange / red) brown (1)

allow: rusty precipitate (1) [2]

(c) (orange / red) brown precipitate (1) [1]

(d) white precipitate (1) [1]

(i) aluminium (1)

sulfate (1) [2]

list principle applies here

6 (a) filter solution (1)

wash with water (1)

dry (1) [3]

do not allow: evaporate to dryness

(b) known volume of oven cleaner (1)

add named acid (1)

with named apparatus (1)

indicator (1)

observe colour change (1)

note volume added (1)

repeat with other sample (1)

valid comparison (1) max [6]





0620 CHEMISTRY








1 (a) suitable collection vessel, e.g. syringe / measuring cylinder, burette, test tube or gas jar in

trough of water or by downward delivery (1) label (1) [2]

(b) tap / separating / dropping funnel (1) [1]

(c) reaction is fast at room temperature (1) [1]

allow: heat not needed / reacts anyway (d) limewater (1)

turns milky / cloudy / white (1) [2]

2 (a) mass of beaker + contents column completed correctly

all 11 correct (2)

10 correct (1)


total loss column correct (1) [3]

note: if all readings are not to 1dp, max 2

time / min mass / g total loss / g 0 95.0 0.0

1 93.0 2.0

2 92.0 3.0

3 91.3 3.7

4 91.2 3.8

5 90.5 4.5

6 90.3 4.7

7 90.1 4.9

8 90.0 5.0

9 90.0 5.0

10 90.0 5.0

(b) points plotted correctly including origin (2)

smooth curve missing anomalous point (1) [3]

(c) gas / carbon dioxide evolved / formed / escapes / given off (1) [1]

(d) (i) result at 4 minutes / fifth point / 91.2 / 3.8 g [1]

(ii) 4.2 (g) ± 0.1 (1) [1]

(e) sketch with steeper graph than original (1)

starting at origin levelling at same height (1) [2]




3 (a) carbon / graphite (1) [1]

(b) bulb lights / fizzing / bubbles (1) [1]

ignore: names of electrodes

allow: solution gets paler / changes colour / green colour fades

(c) copper (1)

negative electrode / cathode (1) [2]

(d) electrolysis (1) [1] 4 (c) table of results

initial temperature boxes completed correctly (1)

21, 22, 22, 19

final temperature boxes correctly completed (1)

41, 16, 11, 32

differences correct (1)

20, –6, –11, 13 [3]

(e) suitable scale – 2 cm is 5 or 10 °C (1)

all 4 bars at correct levels (2),

3 correct (1)


clear unambiguous labels, HJKL or 1, 2, 3, 4 (1) [4]

(f) to remove impurities / clean (1) [1]

(g) (i) Experiment 2 / J (1) [1]

(ii) Experiments 2 / J and 3 / K (1)

temperature decreased / energy or heat is absorbed (1) [2]

(h) (i) (–)5.5 (°C) (1) [1]

(ii) (+)6.5 (°C) (1) [1]

(iii) half amount of solid used (1) [1]

(i) room temperature / initial temperature / 22 °C (1)

reaction finished / all dissolved (1) [2]




(j) carbonate (1)

carbon dioxide (1)

acid (1) max [2]

(k) repeat (1)

compare results / average results / mean (1) [2]

5 tests on solution N

(e) appearance colourless (1) [1]

pH 11–14 (1) [1]

(f) colourless / no change (1)

white (1)

precipitate (1) [3]

(g) litmus paper turns blue (1)

pungent smell (1) [2]

(h) (i) hydrogen / H2 (1) [1]

(ii) ammonia (1) [1]

(i) hydrochloric acid (2) [2]

acid or chloride only, 1 mark.

6 (a) add water (1)

allow: named organic solvent

crush / grind stir / mix / heat plant material / description of (1)

filter (1)

extract each plant material separately / named apparatus (1) [4]

(b) add extract to acid (1)

add extract to alkali (1)

different colours shows suitable indicator (1) [3]

allow: named colours

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