Cambridge International General Certificate of Secondary Education

Cambridge Assessment International Education
Cambridge International General Certificate of Secondary Education

*4970364461*
CHEMISTRY 0620/42
Paper 4 Theory (Extended) February/March 2019
1 hour 15 minutes
Candidates answer on the Question Paper.
No Additional Materials are required.
READ THESE INSTRUCTIONS FIRST
Write your centre number, candidate number and name on all the work you hand in.
Write in dark blue or black pen.
You may use an HB pencil for any diagrams or graphs.
Do not use staples, paper clips, glue or correction fluid.
DO NOT WRITE IN ANY BARCODES.
Answer all questions.

Electronic calculators may be used.
A copy of the Periodic Table is printed on page 16.
You may lose marks if you do not show your working or if you do not use appropriate units.
At the end of the examination, fasten all your work securely together.
The number of marks is given in brackets [ ] at the end of each question or part question.
This syllabus is regulated for use in England, Wales and Northern Ireland as a Cambridge International Level 1/Level 2 Certificate.
This document consists of 14 printed pages and 2 blank pages.
IB19 03_0620_42/4RP
© UCLES 2019 [Turn over
2
1 Period 3 of the Periodic Table is shown.
sodium magnesium aluminium silicon phosphorus sulfur chlorine argon
Answer the following questions using only these elements.

Each element may be used once, more than once or not at all.
State which element:
(a) is a gas at room temperature and pressure
.............................................................................................................................................. [1]
(b) forms a basic oxide with a formula of the form X2O
.............................................................................................................................................. [1]
(c) is made of atoms which have a full outer shell of electrons
.............................................................................................................................................. [1]
(d) forms an oxide which causes acid rain
.............................................................................................................................................. [1]
(e) is extracted from bauxite
.............................................................................................................................................. [1]
(f) forms an oxide which has a macromolecular structure
.............................................................................................................................................. [1]
(g) consists of diatomic molecules.
.............................................................................................................................................. [1]
[Total: 7]
© UCLES 2019 0620/42/F/M/19

3
2 (a) The table gives information about some atoms or ions, A, B and C.
Complete the table.
number of number of electronic

charge
protons electrons structure
A 11 10 2,8
B 18 0
C 10 2,8 –1
[4]
(b) (i) Carbon is an element.
Define the term element.
.............................................................................................................................................
....................................................................................................................................... [1]
6C, 6C and 146C are isotopes of carbon.

12 13
(ii)
Complete the table.
number of protons number of neutrons
6C
12
6C
13
6C
14
[2]
[Total: 7]
© UCLES 2019 0620/42/F/M/19 [Turn over

4
3 Fluorine is a Group VII element. Fluorine forms compounds with metals and non-metals.
(a) Predict the physical state of fluorine at room temperature and pressure.
.............................................................................................................................................. [1]
(b) Fluorine exists as diatomic molecules.
Complete the dot-and-cross diagram to show the electron arrangement in a molecule of

fluorine. Show outer shell electrons only.
F F
[2]
(c) Write a chemical equation for the reaction between sodium and fluorine.
.............................................................................................................................................. [2]
(d) Explain why chlorine does not react with aqueous sodium fluoride.
....................................................................................................................................................
.............................................................................................................................................. [1]
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5
(e) Tetrafluoromethane and lead(II) fluoride are fluorides of Group IV elements. Some properties
of tetrafluoromethane and lead(II) fluoride are shown in the table.
property tetrafluoromethane lead(II) fluoride

formula CF4
melting point / °C –184 855
boiling point / °C –127 1290
conduction of electricity when solid non-conductor non-conductor
conduction of electricity when molten non-conductor good conductor
(i) What is the formula of lead(II) fluoride?
....................................................................................................................................... [1]
(ii) What type of bonding is present between the atoms in tetrafluoromethane?
....................................................................................................................................... [1]
(iii) What type of structure does solid lead(II) fluoride have?
....................................................................................................................................... [1]
(iv) Explain, in terms of attractive forces between particles, why lead(II) fluoride has a much
higher melting point than tetrafluoromethane.
In your answer refer to the types of attractive forces between particles and their relative
strengths.
.............................................................................................................................................
.............................................................................................................................................
.............................................................................................................................................
....................................................................................................................................... [3]

6
(f) Tetrafluoroethene is an unsaturated compound with the formula C2F4.

Tetrafluoroethene is the monomer used to make the polymer poly(tetrafluoroethene).
(i) What is meant by the term unsaturated ?
.............................................................................................................................................
....................................................................................................................................... [1]
(ii) Describe a test to show that tetrafluoroethene is unsaturated.
test .......................................................................................................................................
observations ........................................................................................................................
[2]
(iii) Draw the structure of a molecule of tetrafluoroethene. Show all of the atoms and all of the
bonds.
[1]
(iv) Tetrafluoroethene can be polymerised to form poly(tetrafluoroethene).
Draw one repeat unit of poly(tetrafluoroethene). Show all of the atoms and all of the bonds.
[2]
(v) Deduce the empirical formula of:
tetrafluoroethene ................................................................................................................
poly(tetrafluoroethene). ......................................................................................................
[2]
[Total: 20]
© UCLES 2019 0620/42/F/M/19

7
4 This question is about ethanoic acid, CH3COOH.
(a) Ethanoic acid is manufactured from methanol and carbon monoxide.
CH3OH(g) + CO(g) CH3COOH(g)
The process is done at 200 °C and 30 atmospheres pressure.

The forward reaction is exothermic.
Complete the table using only the words increases, decreases or no change.
effect on the rate of effect on the equilibrium

the forward reaction yield of CH3COOH(g)
adding a catalyst no change
increasing the temperature
decreasing the pressure decreases

[4]
(b) How would you show that an aqueous solution of ethanoic acid is an acid without using an
indicator or measuring the pH?
State the reagent you would use and give the expected observations. Write a chemical equation
for the reaction that you describe.
● reagent
....................................................................................................................................................
● expected observations
....................................................................................................................................................
....................................................................................................................................................
● chemical equation
....................................................................................................................................................
[3]

8
(c) Ethanoic acid is a weak acid.
(i) What is meant by the term acid ?
.............................................................................................................................................
....................................................................................................................................... [1]
(ii) Why is ethanoic acid described as weak ?
.............................................................................................................................................
....................................................................................................................................... [1]
(d) Ethanoic acid reacts with methanol to form an ester.
(i) State two conditions required for this reaction.
1 ..........................................................................................................................................
2 ..........................................................................................................................................
[2]
(ii) Draw the structure of the ester formed when ethanoic acid reacts with methanol. Show all
of the atoms and all of the bonds. Name the ester.
structure
name ...................................................................................................................................
[3]
(iii) Name an ester which is a structural isomer of the ester in (d)(ii).
....................................................................................................................................... [1]
[Total: 15]
© UCLES 2019 0620/42/F/M/19

9
5 Titanium is extracted from an ore called rutile. Rutile is an impure form of titanium(IV) oxide, TiO2.
(a) Rutile is mixed with coke and heated in a furnace through which chlorine gas is passed. The
product is gaseous titanium(IV) chloride, TiCl 4.
TiO2(s) + 2C(s) + 2Cl 2(g) TiCl 4(g) + 2CO(g)
The gaseous titanium(IV) chloride produced is condensed into the liquid state. The
titanium(IV) chloride is then separated from liquid impurities.
(i) Suggest the name of the process by which liquid titanium(IV) chloride could be separated
from the liquid impurities.
....................................................................................................................................... [1]
(ii) Carbon monoxide, CO(g), is also produced in the reaction.
Why should carbon monoxide not be released into the atmosphere?
....................................................................................................................................... [1]
(b) Calculate the volume of chlorine gas, Cl 2(g), at room temperature and pressure, that reacts
completely with 400 g of TiO2(s) using the following steps.
TiO2(s) + 2Cl 2(g) + 2C(s) TiCl 4(g) + 2CO(g)
● Calculate the relative formula mass, Mr, of TiO2.
Mr of TiO2 = ..............................
● Calculate the number of moles in 400 g of TiO2.
.............................. mol
● Determine the number of moles of Cl 2 that react with 400 g of TiO2.
moles of Cl 2 = .............................. mol
● Calculate the volume of Cl 2 that reacts with 400 g of TiO2.
volume of Cl 2 = .............................. dm3

[4]

10
(c) Titanium(IV) chloride, TiCl 4, is heated with an excess of magnesium, in an atmosphere of

argon.
(i) Balance the chemical equation for the reaction.
TiCl 4 + ..... Mg Ti + ..... MgCl 2

[1]
(ii) Titanium(IV) chloride can be reacted with sodium instead of magnesium.
The reaction between titanium(IV) chloride and sodium is similar to the reaction between
titanium(IV) chloride and magnesium.
Write a chemical equation for the reaction between titanium(IV) chloride and sodium.
....................................................................................................................................... [1]
(iii) Suggest why the reaction between titanium(IV) chloride and magnesium is done in an
atmosphere of argon and not in air.
.............................................................................................................................................
....................................................................................................................................... [1]
(d) After titanium(IV) chloride is heated with magnesium, the unreacted magnesium is removed
by adding an excess of dilute hydrochloric acid to the mixture.
The dilute hydrochloric acid also dissolves the magnesium chloride.

The dilute hydrochloric acid does not react with the titanium or dissolve it.
(i) Give two observations and write a chemical equation for the reaction that occurs when
dilute hydrochloric acid reacts with magnesium.
1 ..........................................................................................................................................
2 ..........................................................................................................................................
chemical equation ...............................................................................................................

[3]
(ii) Name the process that is used to separate the titanium from the mixture after all the
magnesium has been removed.
....................................................................................................................................... [1]
(iii) Titanium does not react with the dilute hydrochloric acid or dissolve in it.
Suggest why titanium does not react with dilute hydrochloric acid.
....................................................................................................................................... [1]
© UCLES 2019 0620/42/F/M/19

11
(e) Magnesium cannot be produced by electrolysis of aqueous magnesium chloride using inert
electrodes.
(i) Name the product formed at the negative electrode (cathode) during the electrolysis of
aqueous magnesium chloride.
....................................................................................................................................... [1]
(ii) Suggest how magnesium can be produced from magnesium chloride by electrolysis.
....................................................................................................................................... [1]
[Total: 16]

12
6 This question is about transition elements.
(a) Transition elements are harder and stronger than Group I elements.
Describe two other differences in physical properties between transition elements and Group I
elements.
1 .................................................................................................................................................
2 .................................................................................................................................................
[2]
(b) State one physical property of transition elements that is similar to Group I elements.
.............................................................................................................................................. [1]
(c) State two chemical properties of transition elements.
1 .................................................................................................................................................
2 .................................................................................................................................................
[2]
(d) Cobalt is a transition element. Anhydrous cobalt(II) chloride is used to test for water.
State the colour change that occurs when water is added to anhydrous cobalt(II) chloride.
from ................................................................... to ..................................................................

[2]
(e) Iron is a transition element.
(i) Which two substances react with iron to form rust?
1 ..........................................................................................................................................
2 ..........................................................................................................................................
[2]
(ii) Which metal is used to galvanise iron?
....................................................................................................................................... [1]
© UCLES 2019 0620/42/F/M/19

13
(f) The hull of a ship is made from steel (mainly iron). Metal blocks are placed on the ship’s hull to
prevent rusting.
water water
ship’s hull metal

block
Use your knowledge of the reactivity series to explain why:
● magnesium is suitable to use as the metal blocks

● copper is not suitable to use as the metal blocks.
....................................................................................................................................................
....................................................................................................................................................
.............................................................................................................................................. [2]
(g) Rust contains iron(III) oxide.
Phosphoric acid, H3PO4, can be used to remove rust from an iron object and prevent further
rusting.
(i) Write a chemical equation for the reaction between iron(III) oxide and phosphoric acid to
form iron(III) phosphate and water.
....................................................................................................................................... [2]
(ii) Iron(III) phosphate is an insoluble salt.
Suggest how the formation of iron(III) phosphate prevents further rusting.
.............................................................................................................................................
....................................................................................................................................... [1]
[Total: 15]

14
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© UCLES 2019 0620/42/F/M/19

15
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To avoid the issue of disclosure of answer-related information to candidates, all copyright acknowledgements are reproduced online in the Cambridge
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Cambridge Assessment International Education is part of the Cambridge Assessment Group. Cambridge Assessment is the brand name of the University of
Cambridge Local Examinations Syndicate (UCLES), which itself is a department of the University of Cambridge.
© UCLES 2019 0620/42/F/M/19

The Periodic Table of Elements
Group
© UCLES 2019
I II III IV V VI VII VIII
1 2
H He
hydrogen helium
Key 1 4
3 4 atomic number 5 6 7 8 9 10
Li Be atomic symbol B C N O F Ne
lithium beryllium name boron carbon nitrogen oxygen fluorine neon
7 9 relative atomic mass 11 12 14 16 19 20
11 12 13 14 15 16 17 18
Na Mg Al Si P S Cl Ar
sodium magnesium aluminium silicon phosphorus sulfur chlorine argon
23 24 27 28 31 32 35.5 40
19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36
K Ca Sc Ti V Cr Mn Fe Co Ni Cu Zn Ga Ge As Se Br Kr
potassium calcium scandium titanium vanadium chromium manganese iron cobalt nickel copper zinc gallium germanium arsenic selenium bromine krypton
39 40 45 48 51 52 55 56 59 59 64 65 70 73 75 79 80 84
37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54
Rb Sr Y Zr Nb Mo Tc Ru Rh Pd Ag Cd In Sn Sb Te I Xe
rubidium strontium yttrium zirconium niobium molybdenum technetium ruthenium rhodium palladium silver cadmium indium tin antimony tellurium iodine xenon
16
85 88 89 91 93 96 – 101 103 106 108 112 115 119 122 128 127 131
55 56 57–71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86
0620/42/F/M/19
lanthanoids
Cs Ba Hf Ta W Re Os Ir Pt Au Hg Tl Pb Bi Po At Rn
caesium barium hafnium tantalum tungsten rhenium osmium iridium platinum gold mercury thallium lead bismuth polonium astatine radon
133 137 178 181 184 186 190 192 195 197 201 204 207 209 – – –
87 88 89–103 104 105 106 107 108 109 110 111 112 114 116
actinoids
Fr Ra Rf Db Sg Bh Hs Mt Ds Rg Cn Fl Lv
francium radium rutherfordium dubnium seaborgium bohrium hassium meitnerium darmstadtium roentgenium copernicium flerovium livermorium
– – – – – – – – – – – – –
57 58 59 60 61 62 63 64 65 66 67 68 69 70 71
lanthanoids La Ce Pr Nd Pm Sm Eu Gd Tb Dy Ho Er Tm Yb Lu
lanthanum cerium praseodymium neodymium promethium samarium europium gadolinium terbium dysprosium holmium erbium thulium ytterbium lutetium
139 140 141 144 – 150 152 157 159 163 165 167 169 173 175
89 90 91 92 93 94 95 96 97 98 99 100 101 102 103
actinoids Ac Th Pa U Np Pu Am Cm Bk Cf Es Fm Md No Lr
actinium thorium protactinium uranium neptunium plutonium americium curium berkelium californium einsteinium fermium mendelevium nobelium lawrencium
– 232 231 238 – – – – – – – – – – –
The volume of one mole of any gas is 24 dm3 at room temperature and pressure (r.t.p.).
Cambridge Assessment International Education
Cambridge International General Certificate of Secondary Education
CHEMISTRY 0620/42
Paper 4 Theory (Extended) March 2019
MARK SCHEME
Maximum Mark: 80
Published
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 International will not enter into discussions about these mark schemes.
Cambridge International is publishing the mark schemes for the March 2019 series for most Cambridge
IGCSE™, Cambridge International A and AS Level components and some Cambridge O Level components.
This syllabus is regulated for use in England, Wales and Northern Ireland as a Cambridge International Level 1/Level 2 Certificate.
This document consists of 9 printed pages.
© UCLES 2019 [Turn over

0620/42 Cambridge IGCSE – Mark Scheme March 2019
PUBLISHED
Generic Marking Principles
These general marking principles must be applied by all examiners when marking candidate answers. They should be applied alongside the
specific content of the mark scheme or generic level descriptors for a question. Each question paper and mark scheme will also comply with these
marking principles.
GENERIC MARKING PRINCIPLE 1:
Marks must be awarded in line with:
• the specific content of the mark scheme or the generic level descriptors for the question
• the specific skills defined in the mark scheme or in the generic level descriptors for the question
• the standard of response required by a candidate as exemplified by the standardisation scripts.
Marks awarded are always whole marks (not half marks, or other fractions).
Marks must be awarded positively:
• marks are awarded for correct/valid answers, as defined in the mark scheme. However, credit is given for valid answers which go beyond the
scope of the syllabus and mark scheme, referring to your Team Leader as appropriate
• marks are awarded when candidates clearly demonstrate what they know and can do
• marks are not deducted for errors
• marks are not deducted for omissions
• answers should only be judged on the quality of spelling, punctuation and grammar when these features are specifically assessed by the
question as indicated by the mark scheme. The meaning, however, should be unambiguous.
Rules must be applied consistently e.g. in situations where candidates have not followed instructions or in the application of generic level
descriptors.
© UCLES 2019 Page 2 of 9

PUBLISHED
Marks should be awarded using the full range of marks defined in the mark scheme for the question (however; the use of the full mark range may
be limited according to the quality of the candidate responses seen).
Marks awarded are based solely on the requirements as defined in the mark scheme. Marks should not be awarded with grade thresholds or
grade descriptors in mind.

PUBLISHED
Question Answer Marks
1(a) chlorine / argon 1
1(b) sodium 1
1(c) argon 1
1(d) sulfur 1
1(e) aluminium 1
1(f) silicon 1
1(g) chlorine 1
2(a) 4
number of electrons electronic charge on
protons structure particle
11 10 2,8 M4 1+ / +1(1)
M1 18(1) 18 M3 2,8,8(1) 0
M2 9(1) 10 2,8 1-
2(b)(i) element 1
EITHER (substance) made of atoms with the same atomic number / number of protons / proton number
OR a substance that cannot be split up / broken down into two or more simple(r) substances by chemical means
2(b)(ii) M1 6 protons in all three rows(1) 2

M2 6,7 and 8 neutrons(1)

PUBLISHED
3(a) gas / gaseous 1
3(b) M1 1 shared pair of electrons(1) 2

M2 6 non-bonding electrons on each atom to complete an octet(1)
3(c) 2Na + F2 → 2NaF 2

M1 NaF anywhere(1) M2 equation fully correct(1)
3(d) chlorine less reactive than fluorine ORA 1
3(e)(i) PbF2 1
3(e)(ii) covalent 1
3(e)(iii) giant ionic lattice 1
3(e)(iv) M1(It or lead(II) fluoride) forces of attraction between ions / ionic bonds(1) 3
M2(tetrafluoromethane) forces of attraction between molecules(1)
M3 ionic bonds stronger than attractive forces between molecules / ionic bonds need more energy to break than attractive
forces between molecules(1)
3(f)(i) not all the bonds are single bonds 1
3(f)(ii) M1 bromine / bromine water(1) 2

M2 turns colourless / decolourises(1)
3(f)(iii) 1

PUBLISHED
3(f)(iv) 2
M1 C-C(1)
M2 each C bonded to 2 F and no other atoms + extension bonds(1)
3(f)(v) M1 CF2(1) 2
M2 CF2(1)
4(a) 4
M1 increases(1) No change
M2 increases(1) M3 decreases(1)
decreases M4 decreases(1)
4(b) M1 Suitable metal e.g. magnesium / any carbonate / any base(1) 3
M2 suitable observation e.g. insoluble base / insoluble carbonate / metal dissolve or disappear or metal / carbonate bubbles(1)
M3 balanced equation fully correct(1)
4(c)(i) proton donor 1
4(c)(ii) ionises / dissociates partially or incompletely 1
4(d)(i) M1 heat(1) 2
M2 catalyst / concentrated sulfuric acid(1)

PUBLISHED
4(d)(ii) M1 Correct ester linkage(1) 3
M1 and M2 whole molecule fully correct(2)
M3 methyl ethanoate (1)
4(d)(iii) ethyl methanoate 1
5(a)(i) fractional distillation 1
5(a)(ii) carbon monoxide is toxic/poisonous 1
5(b) • 80 4
• 5
• 10
• 240
5(c)(i) TiCl4 + 2Mg → Ti + 2MgCl2 1

PUBLISHED
5(c)(ii) TiCl4 + 4Na → Ti + 4NaCl 1
5(c)(iii) magnesium burns in air or oxygen OR reacts with air or oxygen / argon is unreactive or inert 1
5(d)(i) M1 / 2 3
bubbles / fizzing / effervescence(1)
M1 / 2 (magnesium or solid) dissolves / disappears / forms solution(1)
M3
Mg + 2HCl → MgCl2 + H2(1)
5(d)(ii) filtration 1
5(d)(iii) titanium is below hydrogen in the reactivity series ORA 1

OR titanium less reactive than hydrogen ORA
OR titanium coated with an oxide layer
5(e)(i) hydrogen 1
5(e)(ii) Heat until magnesium chloride is molten and electrolyse 1
6(a) M1 Transition element has higher melting point / high boiling point ORA(1) 2
M2 Transition element has higher density ORA(1)
6(b) good conduction of heat or electricity OR malleability OR ductility 1
6(c) 1 mark each for any two of: 2
• catalyst
• more than one or different or variable oxidation state / oxidation number / valency
• coloured compounds / coloured ions

PUBLISHED
6(d) from blue(1) to pink(1) 2
6(e)(i) M1 oxygen(1) 2
M2 water(1)
6(e)(ii) zinc / Zn 1
6(f) M1 magnesium above iron / steel in the reactivity series ORA / magnesium more reactive than iron / steel ORA(1) 2
M2 copper below iron / steel in the reactivity series ORA / copper less reactive than iron ORA(1)
6(g)(i) Fe2O3 + 2H3PO4 → 2FePO4 + 3H2O 2

M1 FePO4 anywhere(1) M2 The whole equation correct(1)
6(g)(ii) iron(III) phosphate acts as a barrier which prevents contact between iron and water or air / oxygen 1

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Cambridge Assessment International Education

Cambridge International General Certificate of Secondary Education

READ THESE INSTRUCTIONS FIRST

Answer all questions.

This document consists of 14 printed pages and 2 blank pages.

1 Period 3 of the Periodic Table is shown.

sodium magnesium aluminium silicon phosphorus sulfur chlorine argon

Answer the following questions using only these elements.

State which element:

(a) is a gas at room temperature and pressure

(b) forms a basic oxide with a formula of the form X2O

(c) is made of atoms which have a full outer shell of electrons

(d) forms an oxide which causes acid rain

(e) is extracted from bauxite

(f) forms an oxide which has a macromolecular structure

(g) consists of diatomic molecules.

© UCLES 2019 0620/42/F/M/19

Complete the table.

number of number of electronic

(b) (i) Carbon is an element.

Define the term element.

6C, 6C and 146C are isotopes of carbon.

Complete the table.

number of protons number of neutrons

© UCLES 2019 0620/42/F/M/19 [Turn over

(b) Fluorine exists as diatomic molecules.

Complete the dot-and-cross diagram to show the electron arrangement in a molecule of

© UCLES 2019 0620/42/F/M/19

property tetrafluoromethane lead(II) fluoride

(i) What is the formula of lead(II) fluoride?

(ii) What type of bonding is present between the atoms in tetrafluoromethane?

(iii) What type of structure does solid lead(II) fluoride have?

© UCLES 2019 0620/42/F/M/19 [Turn over

(f) Tetrafluoroethene is an unsaturated compound with the formula C2F4.

(i) What is meant by the term unsaturated ?

(ii) Describe a test to show that tetrafluoroethene is unsaturated.

(iv) Tetrafluoroethene can be polymerised to form poly(tetrafluoroethene).

(v) Deduce the empirical formula of:

© UCLES 2019 0620/42/F/M/19

4 This question is about ethanoic acid, CH3COOH.

(a) Ethanoic acid is manufactured from methanol and carbon monoxide.

CH3OH(g) + CO(g) CH3COOH(g)

The process is done at 200 °C and 30 atmospheres pressure.

effect on the rate of effect on the equilibrium

adding a catalyst no change

increasing the temperature

decreasing the pressure decreases

© UCLES 2019 0620/42/F/M/19 [Turn over

(c) Ethanoic acid is a weak acid.

(i) What is meant by the term acid ?

(ii) Why is ethanoic acid described as weak ?

(d) Ethanoic acid reacts with methanol to form an ester.

(i) State two conditions required for this reaction.

(iii) Name an ester which is a structural isomer of the ester in (d)(ii).

© UCLES 2019 0620/42/F/M/19

TiO2(s) + 2C(s) + 2Cl 2(g) TiCl 4(g) + 2CO(g)

(ii) Carbon monoxide, CO(g), is also produced in the reaction.

Why should carbon monoxide not be released into the atmosphere?

TiO2(s) + 2Cl 2(g) + 2C(s) TiCl 4(g) + 2CO(g)