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® IGCSE is the registered trademark of Cambridge International Examinations.

CAMBRIDGE INTERNATIONAL EXAMINATIONS

Cambridge Ordinary Level

MARK SCHEME for the October/November 2015 series

5070 CHEMISTRY

5070/11 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 O Level – October/November 2015 5070 11

© Cambridge International Examinations 2015

Question Number

Key Question Number

Key

1 B 21 B

2 B 22 A

3 B 23 C

4 D 24 B

5 C 25 A

6 D 26 B

7 C 27 C

8 D 28 B

9 D 29 D

10 B 30 B

11 D 31 C

12 C 32 A

13 C 33 C

14 B 34 D

15 A 35 D

16 A 36 C

17 A 37 D

18 A 38 A

19 D 39 C

20 B 40 C b





5070 CHEMISTRY

5070/12 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






Question Number

Key Question Number

Key

1 C 21 C

2 B 22 C

3 A 23 D

4 C 24 B

5 C 25 A

6 B 26 C

7 D 27 C

8 B 28 D

9 D 29 C

10 D 30 C

11 B 31 A

12 A 32 B

13 B 33 C

14 B 34 D

15 A 35 A

16 B 36 A

17 B 37 C

18 A 38 C

19 B 39 B

20 A 40 D





5070 CHEMISTRY

5070/21 Paper 2 (Theory), maximum raw mark 75

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






A1 (a) argon (1) [1]

(b) chlorine / sulfur dioxide (1) [1]

(d) ammonia (1) [1]

(c) ethene (1) [1]

(e) nitrogen(II) oxide (1) [1]

(f) oxygen (1) [1]

[Total: 6]

A2 (a) three pairs of bonding electrons between H and N (1) [2]

two non-bonding electrons on N (1)

(b) propyl ethanoate (1) [2]

(1)

(c) [2]

C H 0

mole

ratio 12

76.60 /

6.38

1

6.38 /

6.38

16

17.02 /

1.064

simplified

ratio 1.064

6.38 /

6

1.064

6.38 /

6

1.064

1.064 /

1

mole ratio line (1)

simplified ratio or empirical formula (1)

C

C

H

H

H

O

O

CC

H

H

C

H

HH

H

H




(d) (i) sulfur dioxide / SO2 (1) [2]

(sulfur dioxide) dissolves and is oxidised / reacts with (rain)water and oxygen

(1)

(ii) any suitable example e.g. reacts with mortar / reacts with limestone / erodes

buildings (made of carbonate rocks) / corrodes metalwork etc. (1) [1]

(iii) C6H12O6 + 6O2 → 6CO2 + 6H2O [2]

correct reactants and formulae (1)

correctly balanced equation (1)

[Total: 11]

A3 (a) (i) chlorofluorocarbons / CFCs (1) [1]

(ii) ozone absorbs uv (radiation) (1) [2]

too much uv increases incidence of skin cancer / cataracts etc. (1)

(b) (i) reaction catalysed by light / light involved in breakdown of chemicals (1) [1]

(ii) 2O3 → 3O2 (1) [1]

(c) 2Fe

2+ + 2H

+ + O3 → 2Fe

3+ + H2O + O2 (1) [1]

[Total: 6]

A4 (a) positive ions in regular layers with a minimum of two layers of ions (1) [2]

electrons shown interspersed between the particles shown (1)

Marks can be awarded from correct description in writing or from labelled

diagram.

(b) idea of layers of metal atoms / or ions (1) [2]

can slide over each other (when force applied) (1)

+ + + +

+ + + +

+ + + +

e

e e e ee

e e e epositive ion

electron




(c) (i) correct Mr of 128 or ( 2 × 64) as numerator of fraction [2]

OR

correct Mr (2 × 64) + 12 + (16 × 5) + (2 × 1) or 222 as denominator (1)

percentage = 57.65 / 57.7 (1)

(ii) add acid (1) [2]

gas evolved turns limewater milky (1)

(d) A is oxidation because electrons are lost (1) [2]

B is reduction because electrons are gained (1)

[Total: 10]

A5 (a) (i) ANY FOUR FROM: [4]

ammonia molecules / HBr molecules have enough energy to escape from the

HBr(aq) or NH3(aq) (1)

diffusion (1)

molecules move randomly / molecules spread out / molecules get mixed up

(1)

move from high to low concentration / move with the concentration gradient

(1)

solid formed where NH3 and HBr react (1)

HBr has higher Mr than NH3 / molecules of HBr are heavier than molecules of

NH3 (1)

NH3 molecules move faster than HBr molecules / NH3 diffuses faster (1)

(b) higher pressure pushes molecules closer together [1] [Total: 5]

A6 (a) mol of NaOH = 0.30 (1) [2]

energy released (= 0.30 × 57.1) = 17 / 17.1(3) (kJ) (1)

(b) mol of HCl = 2.19 / 36.5 OR = 0.06 (1) [2]

volume = (0.06 / 0.2) = 0.3 dm3

/ 300 cm3 (1)

(c) add nitric acid and silver nitrate (1) [2]

white precipitate / white solid formed (1)




(d) amphoteric (1) [1]

[Total: 7]

B7 (a) weak forces between layers / (weak) van der Waals’ forces between layers (1) [2]

layers slide over each other (easily) (1)

(b) 5 protons and 6 neutrons (1) [1]

(c) giant structure / lattice (1) [2]

(all) bonds are strong / lot of energy needed to break the bonds / needs high

temperature to break the bonds (1)

(d) (i) has delocalised electrons / free electrons / electrons can move (1) [1]

(ii) inert / does not react (with the electrolyte) (1) [1] (e) (i) 4OH

– � O2 + 2H2O + 4e–

(1) [1]

(ii) 2H

+ + 2e

– → H2 (1) [1]

(iii) the mole ratio of H to O in water is 2:1 / for every 2 moles of hydrogen

produced only 1 mole of oxygen is liberated (1) [1]

[Total: 10]

B8 (a) (i) mol Mg (= 0.030 / 24) = 1.25 × 10–3

(1) [3]

mol HCl (= 0.10 × 20 / 1000) = 2 × 10–3

(1)

mol HCl required to react with 1.25 × 10–3

mol Mg is

2.5 × 10–3

so Mg in excess (1)

(ii) bubbles / effervescence / fizzing / tube gets hot / magnesium reduces on

size (1) [1]

(b) mol of gas( = 24 / 24 000) = 1.0 × 10–3

(1) [2]

mass of hydrogen (= 2 × 1.0 × 10–3

) = 2.0 × 10–3

(g)

(c) greater surface area (1) [2]

more frequent collisions (of H+ ions with Mg) (1)

(d) (i) 3Mg(s) + N2(g) → Mg3N2(s) (1) [1]




(ii) 3 – / –3 (1) [1]

[Total: 10]

B9 (a) arrangement: regularly arranged / in a set pattern / ordered / not random / fixed

position (1) [2]

motion: vibrating / do not move (from place to place) (1)

(b) (i) condensation (polymer) (1) [1]

(ii) correct structure with minimum of two units (2) [2]

e.g.

O O

║ ║

- O – □ – C ─ O – □ – C – (as minimum required)

(c) (i) moles methanal (= 1800 / 30) = 60 mol (1) [3]

mass of glycolic acid (= 60 × 76) = 4560 (g) (1)

for 45% yield (= 4560 × 45 / 100) = 2052 (g) (1)

(ii) strong acid is fully ionised / fully dissociated in solution (1) [2]

weak acid is partially ionised / incompletely dissociated in solution (1)

[Total: 10]

B10 (a) position of equilibrium moves to right / more products formed (1) [2]

goes in direction of decreasing number of moles / goes in direction of smaller

volume / fewer moles of products than reactants (1)

(b) position of equilibrium goes to the right / more products formed (1) [2]

reaction is exothermic / backward reaction is endothermic / reaction goes to the

exothermic direction (1)

(c) particles move slower / particles have less energy (1) [2]

fewer particles have activation energy / fewer successful collisions / fewer fruitful

collisions (1)

(d) (i) speeds up reaction (1) [2]

by lowering the activation energy / providing an alternative reaction pathway (1)




(ii) ANY TWO FROM: [2] form coloured compounds (1)

have variable oxidation states / form ions with different charges (1)

form complex ions (1)

[Total: 10]





5070 CHEMISTRY

5070/22 Paper 2 (Theory), maximum raw mark 75







A1 (a) iron (1) [1] (b) iodine (1) [1] (c) sulfur (1) [1] (d) lead (1) [1] (e) argon (1) [1] (f) aluminium / magnesium (1) [1] [Total: 6]

A2 (a) 6CO2 + 6H2O → C6H12O6 + 6O2 (2) [3] 1 mark for correct reactants and products

1 mark for correct balancing (dependent on correct reactants and products)

conditions: chlorophyll and light (1)

(b) (i) glucose / sugars (1) [1] (ii) EITHER [2]

acid (1)

heat / reflux (1)

OR enzymes / amylase (1)

REJECT: other named enzymes which do not hydrolyse starch

at room temperature / temperature any value between 1 °C and 40 °C / pH 7 (1) (c) (i) calcium ethanoate (1) [2]

(CH3COO)2Ca / correct displayed formula (1)

(ii) CH3COOC2H5 shown as displayed formula (1) [1] or C2H5COOCH3 shown as displayed formula (1)

or HCOOC3H7 shown as displayed formula (1)

or HCOOCH(CH3)2 shown as displayed formula (1)




(iii) 1 mark for C = 37.5 / 12 H = 12.5 / 1 O = 50 / 16 [2]

or = 3.125 = 12.5 = 3.125

1 mark for

3.125

3.125

3.125

12.5

3.125

3.125

or 1 4 1

or CH4O

[Total: 11]

A3 (a) carbon for removing smells / removing odours / for removing tastes / so it tastes [2] better (1)

chlorine to kill bacteria / to kill microbes / to kill micro-organisms (1) (b) removal of salt / removal of minerals from (sea) water (1) [1] (c) nitrate and phosphate (1) [1] (d) Ba

2+(aq) + SO4

2–(aq) → BaSO4(s) (2) [2]

1 mark for correct formulae

1 mark for correct state symbols (dependent on correct formulae)

[Total: 6] A4 (a) (i) CO2 + C → 2CO (1) [1] (ii) Fe2O3 + 3CO → 2Fe + 3CO2 (1) [1] (b) to form calcium oxide / to make calcium oxide (1) [1]

(c) ( 100232

356×

×

=) 72.4 % or 72% (2) [2]

2 marks for correct percentage

OR 1 mark for 232 or ((56 × 3) + (16 × 4)) as denominator, or (56 × 3) or 168 as

numerator




(d) anode reaction is oxidation as loss of electrons (1) [2] OR anode reaction is oxidation as oxidation number of oxygen increases (1)

cathode reaction is reduction as gain of electrons (1)

OR cathode reaction is reduction as oxidation number (of iron) decreases (1)

(e) 1 mark each for any two of: [2]

• magnesium more reactive than iron / magnesium higher in the reactivity

series

• magnesium reacts instead of iron / magnesium corrodes instead of iron /

magnesium corrodes preferentially

• magnesium loses electrons instead of iron (f) Fe + 2HCl → FeCl2 + H2 (1) [1] [Total: 10]

A5 (a) (i) 1 mark each for any two of: [2]

• diffusion

• molecules move randomly / molecules spread out / molecules get mixed

up

• (bulk movement of molecules) from high to low concentration / with the

concentration gradient (ii) they have different relative molecular masses / they have different molar [1] masses (1) (b) molecules or particles move faster at higher temperature (or reverse argument) / [2] molecules or particles have more (kinetic) energy at higher temperature (1)

molecules spread out / molecules move further away from each other (on

average) / space between molecules increases (1) [Total: 5]




A6 (a) 9.60 / 32 or 0.3(0) mol S (1) [2]

(247 × 0.30) = 74.1 (kJ) or 74 (kJ) (1)

(b) SO2 + OH

– → HSO3

– (1) [1]

(c) higher concentration of H

+ ions in ethanoic acid / more crowded H

+ ions in [2]

ethanoic acid (or reverse argument) (1)

collision frequency greater in ethanoic acid (or reverse argument) (1)

(d) 3.2 g NaOH = 40

3.2 or 0.08 mol (1) [2]

(0.08 / 0.1) = 0.8 dm3 or 800 (cm

3) (1)

[Total: 7]

B7 (a) (atoms) arranged tetrahedrally / tetrahedral (structure) / (bent) hexagonal [1] (structure) / four atoms round carbon and four atoms round silicon / both giant

(structures) / both lattices / both macromolecules / each has one atoms surrounded

by four others (1) (b) giant structure / lattice (1) [2]

(all) bonds are strong / takes a lot of energy to break bonds / needs high

temperature to break the bonds (1) (c) SiO3

2– (1)

[1] (d) no mobile electrons / does not have delocalised electrons / does not have free [1] electrons / all electrons are used in bonding (1) (e) breakdown / decomposition of substance using electric current (1) [1]

(f) (i) 2O2–

→ O2 + 4e– (1) [1]

(ii) Al

3+ + 3e

– → Al (1) [1]

(g) protons 14 and neutrons 15 (1) [1] (h) (weighted) mass of atom on scale where carbon-12 atom weighs 12 units / idea of [1] mass of an atom comparison with C-12 atom (1) [Total: 10]




B8 (a) 6 × 10–3

mol Cl2 (1) [3]

9.5 × 10–3

mol NaOH (1)

mol NaOH required to react with all chlorine = 12 × 10–3

or mol Cl needed to

react with NaOH = 4.7(5) × 10–3

AND Cl2 in excess (1)

(b) (i) Cl2 + 2KBr → Br2 + 2KCl (2) [2]

1 mark for correct formulae

1 mark for balancing (dependent on correct formulae) (ii) chlorine more reactive than bromine / chlorine above bromine in reactivity [1] series (or reverse argument) (iii) –1 or Cl

– or – (1) [2]

2,8,8 (1)

(c) in solid, the ions are in fixed positions / ions do not move (1) [2]

when molten, the ions can move (1) [Total: 10]

B9 (a) bromine water / aqueous bromine / bromine (1) [2] decolourises / goes colourless (1)

(b) arrangement: not ordered / disordered / no fixed arrangement / no fixed position / [2] random / irregular (shape) (1)

motion: slide over each other / move over each other (1) (c) correct molar masses of isoprene and methylsulfolene: 68 AND 132 or 68 + 64 (1) [3]

100/68 or 1.47 mol isoprene (1)

(× 132) = 194.1 g methylsulfolene (1)

(d) (i) double bond / C=C (bond) (1) [1]

(ii) CO2CH3 [2] |

CH2 = C (2)

|

CH3

1 mark for CH2=C correct; 1 mark for rest of molecule correct [Total: 10]




B10 (a) position of equilibrium moves to the right / moves in forward direction / moves to [2] the product side / moves to make more PCl3 / moves to make more Cl2 (1)

(if pressure decreases) reaction goes in direction of increasing number of moles

(in stoichiometric) equation) / goes in direction of more moles of products /

products have larger (gas) volume than reactants (1) (b) position of equilibrium moves to left moves in backward direction (1) [2]

to reduce the concentration of added substance / to reduce the concentration of

chlorine (1) (c) (i) increasing temperature increases the % of PCl3 (or reverse argument) (1) [1] (ii) reaction is endothermic (because as temperature increases the amount of product [1] increases) (1) (d) no effect / position of equilibrium remains the same (1) [1] (e) molecules move faster / molecules have more energy (1) [2]

more molecules have energy greater than activation energy (1) (f) PCl5 + 4H2O → H3PO4 + 5HCl [1] [Total: 10]





5070 CHEMISTRY

5070/31 Paper 3 (Practical Test), maximum raw mark 40







1 (a) Titration

Accuracy 8 marks

For the two best titres give:

4 marks for a value within 0.2 cm3 of supervisor


1 mark for a value within 0.4 cm3 of supervisor

Concordance 3 marks

Give:

3 marks if all the ticked values are within 0.2 cm3


1 mark if all the ticked values are within 0.4 cm

Average 1 mark

Give 1 mark if the candidate calculates a correct average (error not greater than 0.05)

of all his/her ticked values.

[12]

Assuming a 25.0 cm3 pipette and a titre of 20.2 cm

3.

(b) moles of sodium hydroxide in 25 cm3 of Q

= 1000

0.33625×

= 0.0084 [1]

(c) moles of hydrochloric acid reacting with 25 cm3 of Q

= 0.0084 [1]

(d) moles of hydrochloric acid in 250 cm3 of P

= 20.2

2500.0084×

= 0.104 [1]

(e) moles of hydrochloric acid in 250 cm3 0.500 mol / dm

3 acid

= 1000

0.5250×

= 0.125 [1]




(f) moles of hydrochloric acid that reacted with calcium carbonate = 0.125 – 0.104

= 0.021 [1]

(g) mass of calcium carbonate in one tablet = 22

1000.021

×

×

= 0.525 g

If the answer from (f) undergoes any one of the following processes, score 1 mark

If answer from (f) undergoes all of the following processes, score 2 marks

(f) / 2 mole of calcium carbonate

(f) × 100 mass of calcium carbonate

(f) / 2 moles in 1 tablet

[2]

[Total: 19]




2 R is dilute hydrochloric acid; S is manganese(IV) oxide

Test Notes

General points For precipitate/ppt

Allow solid, suspension, powder

For gases

Name of gas requires test to be at least partially correct.

Effervesces = bubbles = gas vigorously evolved but not gas evolved.

Solutions

Colourless not equivalent to clear, clear not equivalent to colourless.

Solution R

Test 1

white ppt (1)

Test 2

insoluble in acid (1)

Test 3

ppt dissolves (1)

colourless solution (1)

Test 4

(a) effervescence (1)

turns limewater milky (1)

carbon dioxide (1)

solid disappears (1)

(b) white ppt (1)

ppt dissolves (1)

colourless solution (1)

To score carbon dioxide mark there must be

some indication of a test e.g. ‘tested with

lime water’

Test 5

(a) white ppt (1)

(b) ppt disappears (1)




Test 6

(a) bubbles (1)

relights a glowing splint (1)

oxygen (1)

to score oxygen mark there must be some

indication of a test e.g. ‘tested with a

glowing splint’, ‘relights a (burning) splint’

Test 7

(a) yellow/brown filtrate (1)

(b) liquid turns blue/black (1)

Test 8

litmus turns white/bleached (1)

chlorine (1)

to score chlorine mark there must be some

indication of the gas e.g. ‘smell of chlorine’

Any 19 out of 20 points to score. [19]

R contains hydrochloric acid/hydrogen chloride / HCl (dependent on white ppt in test 1;

insoluble in acid in test 2 or chlorine identified in test 8; and bubbling / gas in test 4) (1)

S is an oxidising agent/oxidant (dependent on indication of iodine in test 7 or chlorine in

test 8) (1)

[2]

[Total: 21]





5070 CHEMISTRY

5070/32 Paper 3 (Practical Test), maximum raw mark 40







1 (a) Titration

Accuracy 8 marks

For the two best titres give:



1 mark for a value within 0.4 cm3 of supervisor

Concordance 3 marks

Give:



1 mark if all the ticked values are within 0.4 cm3

Average 1 mark

Give 1 mark if the candidate calculates a correct average (error not greater than 0.05)

of all his / her ticked values. [12]

Assuming a 25.0 cm3 pipette and a titre of 20.2 cm

3.

(b) moles of sodium hydroxide in 25 cm3 of Q

= 1000

0.527 25 ×

= 0.0132 [1]

(c) moles of hydrochloric acid reacting with 25 cm3 of Q

= 0.0132 [1]

(d) moles of hydrochloric acid in 110 cm3 of P

= 20.2

110 0.0132 ×

= 0.0719 [1]

(e) moles of hydrochloric acid in 100 cm3 1 mol / dm

3 acid

= 1000

1 100 ×

= 0.1 [1]




(f) moles of hydrochloric acid that reacted with magnesium hydroxide = 0.1 – 0.0719

= 0.0281 [1]

(g) concentration in g / dm3 of magnesium hydroxide =

2

0.0281 × 58 ×

10

1000 g

= 78.7 g

If the answer from (f) undergoes any one of the following processes, score 1 mark

If answer from (f) undergoes all of the following processes, score 2 marks

(f) / 2 mole of magnesium hydroxide reacting

(f) × 58 mass of magnesium hydroxide

(f) × 1000 / 10 mole in 1 dm3

[2]

[Total: 19]




2 R is dilute sulfuric acid; S is copper(II) oxide

Test Notes

General points For precipitate/ppt

allow solid, suspension, powder

For gases

Name of gas requires test to be at least partially correct

Effervesces = bubbles = gas vigorously evolved but not gas evolved

Solutions

Colourless not equivalent to clear, clear not equivalent to colourless

Solution R

Test 1

(a) white ppt (1)

(b) ppt remains (1)

Test 2

(a) bubbles (1)

‘pops’ with a lighted splint (1)

hydrogen (1)

solid disappears (1)

(b) white ppt (1)

insoluble in excess (1)

to score hydrogen mark there must be

some indication of a test e.g. ‘gas pops’

(with a splint), ‘test with lighted splint’

Test 3

blue solution (1)

Test 4

blue ppt (1)

soluble in excess (1)

dark / deep blue solution (1)




Test 5 (a) (solution / liquid) turns yellow / brown (1)

ppt (1)

(b) decolourised (1)

solid (remains) (1)

Test 6

(a) no reaction / few bubbles / solid insoluble (1)

(b) bubbles (1)

relights a glowing splint (1)

oxygen (1)

to score oxygen mark there must be some

indication of a test e.g. ‘tested with a

glowing splint’, ‘relights a (burning) splint’

Any 19 out of 20 points to score. [19]

R contains sulfuric acid / hydrogen sulfate / H2SO4 (dependent on white ppt insoluble in acid in

test 1 and bubbling in test 2) (1)

Cation in S is copper(II) / Cu2+

(dependent on blue in test 3 or blue ppt / deep blue solution in

test 4) (1)

[2]

[Total: 21]





5070 CHEMISTRY

5070/41 Paper 4 (Alternative to Practical), maximum raw mark 60







1 (a) (i) propanol (1) [1]

(ii) catalyst / speeds up reaction (1) [1]

(iii) displayed formula of propene (1) [1]

(b) (aqueous) bromine (1)

(turns) colourless / decolourises (1) [2]

(c) (i) carbon dioxide (1)

limewater turns milky / limewater forms a white precipitate (1) [2]

(ii) 2C3H6 + 9O2 → 6CO2 + 6H2O

species (1) balancing (1) [2]

[Total: 9]

2 (a) hydrogen (1)

lighted splint pops / pops in a flame (1) [2]

(b) (i) chlorine (1) [1]

(ii) 2Cl

– → Cl2 + 2e

– or 2Cl

– – 2e

– → Cl2 (1) [1]

(c) (i) oxygen (1)

glowing splint relights (1) [2]

(ii) 4OH– → 2H2O + O2 + 4e

– or 4OH

– – 4e

– → 2H2O + O2 (1) [1]

[Total: 7]

3 (b) [Total: 1]

4 (b) [Total: 1]

5 (d) [Total: 1]




6 (a) 3.43 (g) (1) [1]

(b) volumetric flask / standard flask / graduated flask (1) [1]

(c) (i) pipette (1) [1]

(ii) purple / pink (1) [1]

(d) 27.3 37.9 42.7 one mark for each correct row or column

0.0 10.0 15.6 to the benefit of the candidate (3)

27.3 27.9 27.1

average volume = 27.2 (cm3) (1) [4]

(e) 0.000544 (mol) (1) [1]

(f) 0.00136 (mol) (1) [1]

(g) 0.0272 (mol) (1) [1]

(h) 126 (1) [1]

(i) Mr of H2C2O4 = 90

126 – 90 = 36 (1)

36 / 126 × 100 = 28.6 (%) (1) [2]

[Total: 14]

7 (a) transition metal present / transition element present /

Z is a compound of a transition metal / Z is a compound of a transition element (1) [1]

(b) (i) blue precipitate (1)

(ii) insoluble in excess (1) [2]

(c) (i) blue precipitate (1)

(ii) deep/dark blue solution formed (1) [2]

(d) (dilute / aqueous) nitric acid (1)

(aqueous) silver nitrate (1)

white precipitate (1) [3]




(e) CuCl2 (1) [1]

[Total: 9]

8 (a) to reach room temperature / steady temperature (1) [1]

(b) exothermic (1) [1]

(c) all sodium hydroxide has reacted / reaction is complete (1) [1]

(d) all points plotted correctly (1)

one mark each for two intersecting straight lines (2) [3]

(e) (i) 26.0 (cm3) (1) [1]

(ii) 31.8 (°C) (1) [1]

(f) (i) 2NaOH + H2SO4 → Na2SO4 + 2H2O (1) [1]

(ii) 0.05 moles of NaOH react with 0.025 moles of H2SO4 (1)

concentration of H2SO4 = 0.96 (mol / dm³) (1) [2]

(g) (i) 7.6 (°C) (1) [1]

(ii) 76 (cm3) (1) [1]

(iii) moles of NaOH = 0.05 (1)

∆H = 48.5 (kJ / mol) (1) [2]

(h) heat or evaporate / warm or boil / leave in sun (1)

to crystallisation point / saturation point / leave some of water / leave (solution) to

cool / leave (solution) to crystallise / leave a concentrated solution (1)

wash and dry crystals (1) [3]

[Total: 18]





5070 CHEMISTRY

5070/42 Paper 4 (Alternative to Practical), maximum raw mark 60







1 (a) (gas) syringe (1) [1]

(b) (i) hydrogen (1) [2]

burning splint pops or pops in a flame (1)

(ii) Zn + H2SO4 → ZnSO4 + H2 (1) [1]

(c) (i) 0.004 (mol) (1) [1]

(ii) 0.26 (g) (1) [1]

(iii) 0.94 (g) (1) [1]

(d) (copper) wet / not dried / some solution remaining (1) [1]

[Total: 8]

2 (a) (i) cracking (1) [1]

(ii) catalyst / speeds up reaction (1) [1]

(iii) C8H18 (1) [1]

(iv) C2H4 with any one other viable product in a balanced equation (1)

e.g. C8H18 → C2H4 + C6H14 or 2C2H4 + C4H10

or 3C2H4 + C2H6 or 4C2H4 + H2 [1]

(b) (i) (turns) colourless / decolourises (1) [1]

(ii) addition (1) [1]

(iii) C2H4 + Br2 → C2H4Br2 / correct structural formula (1) [1]

(c) carbon dioxide (1)

limewater turns milky or forms a white ppt. (1) [2]

[Total: 9]

3 (d) (1) [Total: 1]

4 (b) (1) [Total: 1]

5 (c) (1) [Total: 1]

6 (a) (1) [Total: 1]




7 (a) 1.82 (g) (1) [1]

(b) volumetric flask / standard flask / graduated flask (1) [1]

(c) (before) yellow to (after) orange or red or pink or a combination e.g. orange / red (1) [1]

(d) 19.8 29.1 46.7 one mark for each correct row or column

0.0 10.0 27.4 to the benefit of the candidate (3)

19.8 19.1 19.3

mean titre 19.2 (cm3) (1) [4]

(e) 0.00192 (mol) (1) [1]

(f) Na2CO3 + 2HCl → 2NaCl + CO2 + H2O (1) [1]

(g) 0.00096 (mol) (1) [1]

(h) 0.0096 (mol) (1) [1]

(i) 1.018 or 1.02 (g) (1) [1]

(j) 0.8(0) (g) (1) [1]

(k) 44(.0) % (1) [1]

[Total: 14]

8 (a) L does not contain a transition metal / transition element / transition metal

compound / transition metal ions (1) [1]

(b) (i) white ppt (1)

(ii) soluble in excess / forms a solution (1) [2]

(c) (i) white ppt (1)

(ii) insoluble in excess (1) [2]

(d) (dilute / aqueous) nitric / hydrochloric acid (1)

(aqueous) barium nitrate / chloride / hydroxide (1)

white ppt (1) [3]




(e) Al2

(SO4)3 (1) [1]

[Total: 9]

9 (a) 2Cu + O2 → 2CuO (1) [1]

(b) nitrogen (1) [1]

(c) (i) all points plotted correctly (1)

ruled straight line of best fit (1)

passing through the origin (1) [3]

(ii) point at 50, 45 circled (1) [1]

(iii) value in range 39–41 cm3 only (1) [1]

(iv) gas not been passed until all oxygen is used up / copper has not been heated

long enough / there is not enough copper / oxygen in excess / gas is not

allowed to cool (1) [1]

(d) (i) 20(.0)(cm3) allow correctly read value from candidate’s graph (1) [1]

(ii) 44(.0)(cm3) allow correctly read value from candidate’s graph (1) [1]

[Total: 10]

10 (a) sulfuric acid (1) [1]

(b) CuO + H2SO4 → CuSO4 + H2O (1) [1]

(c) blue (1) [1]

(d) heat / evaporate / warm / boil / leave in sun (1) [1]

to crystallisation point / saturation point / leave some of water / leave solution to

cool / leave solution to crystallise / leave a concentrated solution (1) [1]

wash and dry crystals (1) [1]

[Total: 6]

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