Đề thi Cambridge IGCSE™ chính thức môn Hoá tháng 062023 (Đề tự luận_Số 31_ Cơ bản_Có đáp án)

Cambridge IGCSE™

*7173648614*

CHEMISTRY0620/31
May/June 2023

Paper 3 Theory (Core)

1 hour 15 minutes


You must answer on the question paper.
No additional materials are needed.

INSTRUCTIONS
● Answer all questions.
● Use a black or dark blue pen. You may use an HB pencil for any diagrams or graphs.
● Write your name, centre number and candidate number in the boxes at the top of the page.
● Write your answer to each question in the space provided.
● Do not use an erasable pen or correction fluid.
● Do not write on any bar codes.
● You may use a calculator.
● You should show all your working and use appropriate units.

INFORMATION
● The total mark for this paper is 80.
● The number of marks for each question or part question is shown in brackets [ ].
● The Periodic Table is printed in the question paper.

This document has 16 pages.

IB23 06_0620_31/2RP
© UCLES 2023

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2
1Fig. 1.1 shows part of the Periodic Table.
I

II

III IV

V

VI VII VIII

H

He
C

Na Mg
K Ca

N

O

Al
Fe

Cu

Cl
Br
I

Fig. 1.1
Answer the following questions using only the elements in Fig. 1.1.
Each symbol of the element may be used once, more than once or not at all.
Give the symbol of the element that:












(a)forms 78% by volume of clean, dry air
............................................................................................................................................... [1]
(b)has an atom with a complete outer electron shell
............................................................................................................................................... [1]
(c) has an atom with five occupied electron shells

............................................................................................................................................... [1]
(d)forms an ion with a charge of 2–
............................................................................................................................................... [1]
(e)forms an ion that gives a green precipitate on addition of aqueous sodium hydroxide
............................................................................................................................................... [1]
(f)is used in food containers because of its resistance to corrosion.



............................................................................................................................................... [1]



[Total: 6]

© UCLES 2023

0620/31/M/J/23


3
2

(a)Table 2.1 shows some properties of the halogens.
Table 2.1

halogen

melting point
in °C

boiling point
in °C

density at room
temperature and
pressure in g / cm3

fluorine

–220

–188

0.0016

chlorine

–101

–35

0.0032

+59

3.1

bromine
iodine

+114

+184

Use the information in Table 2.1 to predict:


(i)the melting point of bromine




��������������������������������������������������������������������������������������������������������������������������������������� [1]
(ii)the density of iodine at room temperature and pressure




��������������������������������������������������������������������������������������������������������������������������������������� [1]
(iii)the physical state of chlorine at –10 °C. Give a reason for your answer.



physical state .......................................................................................................................

reason ..................................................................................................................................

..............................................................................................................................................
[2]

(b)The equation for the reaction of aqueous chlorine with aqueous potassium iodide is shown.
Cl 2 + 2KI → I2 + 2KCl


(i)Choose the word which best describes this type of chemical reaction.
Draw a circle around your chosen answer.
addition




displacement

neutralisation

polymerisation[1]

(ii)Explain why aqueous iodine does not react with aqueous potassium chloride.



© UCLES 2023

........................................................................................................................................ [1]

0620/31/M/J/23

[Turn over

4


(c) Complete the diagram in Fig. 2.1 to show the electronic configuration of a chlorine atom.

Cl

Fig. 2.1
[1]


(d)Describe a test for chlorine.

test ..............................................................................................................................................
observations ...............................................................................................................................
[2]


© UCLES 2023

[Total: 9]

0620/31/M/J/23


5
3

(a)Water from natural sources contains dissolved gases.

Choose from the list, the gas that is essential for aquatic life.
Draw a circle around your chosen answer.
argon





oxygen[1]

(i)Name one other harmful substance which is present in polluted water.
........................................................................................................................................ [1]
(ii)State why nitrates are harmful to aquatic life.




nitrogen

(b)Polluted water may contain harmful substances such as metal compounds, plastics, nitrates
and phosphates.




hydrogen

........................................................................................................................................ [1]

(c)Table 3.1 shows the masses of ions, in mg, present in a 1000 cm3 sample of polluted water.
Table 3.1
formula
of ion

mass of ion present
in mg / 1000 cm3
of polluted water

NH4+

0.5

calcium

Ca2+

2.2

chloride

Cl –

2.5

HCO3–

12.0

magnesium

Mg2+

0.8

nitrate

NO3–

0.4

K+

8.3

silicate

SiO32–

8.0

sodium

Na+

10.2

sulfate

SO42–

0.2

tin(II)

Sn2+

0.4

name of ion

hydrogencarbonate

potassium

Answer these questions using information from Table 3.1.


(i)Name the negative ion present in the highest concentration.




........................................................................................................................................ [1]
(ii)State the name of the NH4+ ion.



© UCLES 2023

........................................................................................................................................ [1]

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6


(iii)Calculate the mass of calcium ions present in 200 cm3 of polluted water.




mass = .............................. mg [1]
(d)Copper(II) sulfate can be used to test for the presence of water.
CuSO4(s) + 5H2O(l)

CuSO4•5H2O(s)


anhydroushydrated
copper(II) sulfate
copper(II) sulfate


(i)State the meaning of the term hydrated.

........................................................................................................................................ [1]
(ii)Describe how hydrated copper(II) sulfate is changed to anhydrous copper(II) sulfate.




........................................................................................................................................ [1]
(e)Complete the symbol equation for the reaction of sodium with water.



2Na + .....H2O → 2NaOH + ............



© UCLES 2023

[2]
[Total: 10]

0620/31/M/J/23


7
4This question is about sulfur and compounds of sulfur.


(a)Sulfur has several isotopes.

Define the term isotopes.



.....................................................................................................................................................



............................................................................................................................................... [2]



(b) Deduce the number of protons, neutrons and electrons in the sulfide ion shown.
36 2–
16S



number of protons ......................................................................................................................



number of neutrons ....................................................................................................................


number of electrons ....................................................................................................................
[3]

(c)Sulfur burns in oxygen to produce sulfur dioxide.

Fig. 4.1 shows an incomplete reaction pathway diagram for this reaction.

energy

progress of reaction
Fig. 4.1


(i)Complete Fig. 4.1 by writing these formulae on the diagram:
● S + O2
● SO2.[1]



(ii)Explain how Fig. 4.1 shows that the reaction is exothermic.



..............................................................................................................................................



........................................................................................................................................ [1]

(iii)Complete this sentence about an exothermic reaction using a word from the list.
products

reactants

sulfur

surroundings

An exothermic reaction transfers thermal energy to the ............................. .
© UCLES 2023

0620/31/M/J/23

[1]
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8


(d)Fig. 4.2 shows the apparatus used for the electrolysis of dilute sulfuric acid using graphite
electrodes.

power
+ supply –
Fig. 4.2

(i)Label Fig. 4.2 to show:
● the cathode
● the electrolyte.

[2]

(ii)Name the products and state the observations at the positive and negative electrodes.



product at the positive electrode



..............................................................................................................................................



observations at the positive electrode



..............................................................................................................................................



product at the negative electrode

..............................................................................................................................................



observations at the negative electrode


..............................................................................................................................................
[4]


(e)Complete the word equation for the reaction of dilute sulfuric acid with sodium carbonate.
sulfuric
acid

+

sodium
carbonate

........................
........................

+

........................

+

........................

........................

[3]


(f)A few drops of thymolphthalein indicator are added to dilute sulfuric acid.

State the colour of the solution.


............................................................................................................................................... [1]



[Total: 18]

© UCLES 2023

0620/31/M/J/23


9
5
This question is about metals.
(a)Iron is a transition element. Potassium is an element in Group I of the Periodic Table.
State two differences in the physical properties of iron compared to potassium.
1 ..................................................................................................................................................
2 ..................................................................................................................................................

[2]


(b)Carbon is used to extract iron from iron ore in a blast furnace.

State two uses of carbon in the extraction process.
1 ..................................................................................................................................................
2 ..................................................................................................................................................
[2]



(c)Steel is an alloy of iron.
(i)State the meaning of the term alloy.



..............................................................................................................................................



........................................................................................................................................ [1]



(ii)State why alloys are more useful than pure metals.



........................................................................................................................................ [1]

(d) T
 able 5.1 shows the observations made when four different metals react with dilute hydrochloric
acid of the same concentration.
Table 5.1
metal

observations

iron

bubbles form slowly

lead

no bubbles formed

magnesium

bubbles form rapidly

nickel

bubbles form very slowly

Put the four metals in order of their reactivity.

Put the least reactive metal first.

least reactive

most reactive

[2]

© UCLES 2023

[Total: 8]
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10
6(a)A student investigates the reaction of small pieces of zinc of the same mass and size with three
different concentrations of dilute hydrochloric acid in the presence of a catalyst.
The three concentrations of dilute hydrochloric acid are:
● 1.0 mol / dm3
● 1.5 mol / dm3
● 2.0 mol / dm3.
All other conditions stay the same.


Table 6.1 shows the time taken for each reaction to finish.
Table 6.1
concentration of hydrochloric acid
in mol / dm3

time taken for the reaction to finish

in s
200
100
150



(i) C
 omplete Table 6.1 by writing the concentrations of hydrochloric acid in the first column.
[1]



(ii) D
 escribe the effect on the time taken for the zinc to finish reacting with 2.0 mol / dm3
hydrochloric acid with no catalyst present.

All other conditions stay the same.


........................................................................................................................................ [1]



(iii) D
 escribe the effect on the time taken for the zinc to finish reacting with 2.0 mol / dm3
hydrochloric acid when the surface area of the zinc is increased.

All other conditions stay the same.

........................................................................................................................................ [1]



(b)Crystals of zinc chloride can be prepared by reacting excess zinc with dilute hydrochloric acid.

Choose from the list, the method used to separate the unreacted zinc from the reaction mixture.
Draw a circle around your chosen answer.


© UCLES 2023

chromatography

crystallisation

0620/31/M/J/23

evaporation

filtration[1]


11


(c)Zinc chloride is soluble in water.

Choose one other compound that is soluble in water.

Tick (✓) one box.


calcium carbonate

lead(II) chloride


silver chloride


sodium nitrate
[1]


© UCLES 2023

[Total: 5]

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[Turn over


12
7(a)Fig. 7.1 shows the displayed formula of mesaconic acid.
H
C

H

C

H
H

O

O

C

C

C

O

H

H

O
Fig. 7.1


(i)On Fig. 7.1 draw a circle around one carboxylic acid functional group.

(ii)Deduce the molecular formula of mesaconic acid.




[1]

........................................................................................................................................ [1]
(iii)Mesaconic acid is a colourless compound.

Describe the colour change when excess mesaconic acid is added to aqueous bromine.



from ............................................................ to ������������������������������������������������������������� [2]
(b)Ethanoic acid belongs to the homologous series of carboxylic acids.



Define the term homologous series.



.....................................................................................................................................................



............................................................................................................................................... [2]

(c)Complete the word equation for the reaction of ethanoic acid with magnesium.
ethanoic
acid

+

magnesium

........................

+

........................

........................

[2]

© UCLES 2023

0620/31/M/J/23


13

(d)Ethanoic acid reacts with ethanol.
The organic product has the molecular formula C4H8O2.
Complete Table 7.1 to calculate the relative molecular mass of C4H8O2.
Table 7.1




atom

number of atoms

relative
atomic mass

carbon

4

12

hydrogen

1

oxygen

16

4 × 12 = 48

relative molecular mass = .............................. [2]
(e)Ethanol can be manufactured by fermentation.

Complete the word equation for one other method of manufacturing ethanol.


................................ + ................................ → ethanol



© UCLES 2023

[2]
[Total: 12]

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14
8This question is about nitrogen and compounds of nitrogen.


(a)Nitrogen is a non-metal. Nitrogen is a poor electrical conductor.

Describe two other physical properties which are typical of non-metals.
1 ..................................................................................................................................................
2 ..................................................................................................................................................
[2]

(b)Oxides of nitrogen are air pollutants which contribute to acid rain.
(i)State one source of oxides of nitrogen in the air.




........................................................................................................................................ [1]
(ii)State one other adverse effect of oxides of nitrogen.





........................................................................................................................................ [1]
(c)Ammonia is a simple molecule with covalent bonds.
(i)Describe a covalent bond.



..............................................................................................................................................



........................................................................................................................................ [2]



(ii)Complete Fig. 8.1 to show the dot-and-cross diagram for a molecule of ammonia.

Show outer shell electrons only.

H

N

H

H

Fig. 8.1
[2]

© UCLES 2023

0620/31/M/J/23


15


(iii)Aqueous ammonia is alkaline.

Choose from the list, the pH value that is alkaline.
Draw a circle around your chosen answer.
pH 1




pH 5

pH 7

pH 10[1]

(iv)Aqueous ammonia releases ammonia gas.

Ammonia gas turns damp red litmus paper blue.
A long glass tube is set up as shown in Fig. 8.2.
long glass tube

cotton wool soaked
in aqueous ammonia

damp red
litmus paper
Fig. 8.2


At first, the litmus paper does not turn blue.
After a short time, the litmus paper turns blue.
Explain these results in terms of the kinetic particle theory.


..............................................................................................................................................



..............................................................................................................................................

..............................................................................................................................................



..............................................................................................................................................



........................................................................................................................................ [3]



[Total: 12]

Permission to reproduce items where third-party owned material protected by copyright is included has been sought and cleared where possible. Every
reasonable effort has been made by the publisher (UCLES) to trace copyright holders, but if any items requiring clearance have unwittingly been included, the
publisher will be pleased to make amends at the earliest possible opportunity.
To avoid the issue of disclosure of answer-related information to candidates, all copyright acknowledgements are reproduced online in the Cambridge
Assessment International Education Copyright Acknowledgements Booklet. This is produced for each series of examinations and is freely available to download
at www.cambridgeinternational.org after the live examination series.
Cambridge Assessment International Education is part of Cambridge Assessment. Cambridge Assessment is the brand name of the University of Cambridge
Local Examinations Syndicate (UCLES), which is a department of the University of Cambridge.

© UCLES 2023

0620/31/M/J/23

© UCLES 2023

12

V

Cr

Mn

Co

27

Ni

28

Cu

29

Zn

30

Fe

57–71

56

55

0620/31/M/J/23

104

88

–

90

89

232

thorium

actinium

–

Th

Ac

140

cerium

139

lanthanum

59

231

protactinium

Pa

91

141

praseodymium

Pr

–

58

Ce

–

Db

dubnium

Rf

rutherfordium

La

57

actinoids

105

181

tantalum

Ta

73

93

niobium

Nb

41

51

vanadium

238

uranium

U

92

144

neodymium

60

Nd

–

Sg
seaborgium

106

184

tungsten

W

74

96

molybdenum

Mo

42

52

chromium

–

neptunium

Np

93

–

promethium

61

Pm

–

Bh
bohrium

107

186

rhenium

Re

75

–

technetium

Tc

43

55

manganese

–

plutonium

Pu

94

150

samarium

62

Sm

–

Hs
hassium

108

190

osmium

Os

76

101

ruthenium

Ru

44

56

iron

–

americium

Am

95

152

europium

63

Eu

–

Mt
meitnerium

109

192

iridium

Ir

77

103

rhodium

Rh

45

59

cobalt

–

curium

Cm

96

157

gadolinium

64

Gd

–

Ds
darmstadtium

110

195

platinum

Pt

78

106

palladium

Pd

46

59

nickel

The volume of one mole of any gas is 24 dm3 at room temperature and pressure (r.t.p.).

actinoids

lanthanoids

–

Ra

radium

Fr

francium

89–103

178

87

137

hafnium

133

barium

Hf

caesium

lanthanoids

Ba

72

91

zirconium

Zr

40

48

titanium

Cs

89

yttrium

88

strontium

85

rubidium

Y

39

45

Sr

38

40

Ca

Rb

37

39

K

scandium

–

berkelium

Bk

97

159

terbium

65

Tb

–

Rg

roentgenium

111

gold

197

Au

79

108

silver

Ag

47

64

copper

–

californium

Cf

98

163

dysprosium

66

Dy

–

Cn
copernicium

112

201

mercury

Hg

80

112

cadmium

Cd

48

65

zinc

calcium

Ti

26

potassium

Sc

25

31

24

–

einsteinium

Es

99

165

holmium

67

Ho

–

Nh
nihonium

113

204

thallium

Tl

81

115

indium

In

49

70

gallium

Ga

27

20

24

19

23

aluminium

Al

13

11

boron

magnesium

23

1

sodium

22

B

C

N

7

O

8

VI

F

9

VII

2

VIII

–

fermium

Fm

100

167

erbium

68

Er

–

Fl

flerovium

114

lead

207

Pb

82

tin

119

Sn

50

73

germanium

Ge

32

28

silicon

Si

14

12

carbon

–

mendelevium

Md

101

169

thulium

69

Tm

–

Mc
moscovium

115

209

bismuth

Bi

83

122

antimony

Sb

51

75

arsenic

As

33

31

phosphorus

P

15

14

nitrogen

–

nobelium

No

102

173

ytterbium

70

Yb

–

Lv
livermorium

116

–

polonium

Po

84

128

tellurium

Te

52

79

selenium

Se

34

32

sulfur

S

16

16

oxygen

–

Lr

lawrencium

103

175

lutetium

71

Lu

–

Ts
tennessine

117

–

astatine

At

85

127

iodine

I

53

80

bromine

Br

35

35.5

chlorine

Cl

17

19

fluorine

–

oganesson

Og

–

118

radon

86

Rn

131

xenon

54

Xe

84

krypton

36

Kr

40

argon

18

Ar

20

neon

Ne

10

4

helium

6

V

hydrogen

5

IV

He

Mg

21

relative atomic mass

name

atomic symbol

atomic number

Key

III

H

1

Na

9

11

7

Be

beryllium

Li

4

3

lithium

II

I

Group

The Periodic Table of Elements

16


Cambridge IGCSE™
CHEMISTRY

0620/31

Paper 3 Theory (Core)

May/June 2023

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 May/June 2023 series for most
Cambridge IGCSE, Cambridge International A and AS Level and Cambridge Pre-U components, and some
Cambridge O Level components.

This document consists of 13 printed pages.
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Cambridge IGCSE – Mark Scheme
PUBLISHED
Generic Marking Principles

May/June 2023

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.

GENERIC MARKING PRINCIPLE 2:
Marks awarded are always whole marks (not half marks, or other fractions).
GENERIC MARKING PRINCIPLE 3:
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.

GENERIC MARKING PRINCIPLE 4:
Rules must be applied consistently, e.g. in situations where candidates have not followed instructions or in the application of generic level
descriptors.

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Cambridge IGCSE – Mark Scheme
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GENERIC MARKING PRINCIPLE 5:
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).
GENERIC MARKING PRINCIPLE 6:
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.

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Cambridge IGCSE – Mark Scheme
PUBLISHED

May/June 2023

Science-Specific Marking Principles
1

Examiners should consider the context and scientific use of any keywords when awarding marks. Although keywords may be present, marks
should not be awarded if the keywords are used incorrectly.

2

The examiner should not choose between contradictory statements given in the same question part, and credit should not be awarded for
any correct statement that is contradicted within the same question part. Wrong science that is irrelevant to the question should be ignored.

3

Although spellings do not have to be correct, spellings of syllabus terms must allow for clear and unambiguous separation from other
syllabus terms with which they may be confused (e.g. ethane / ethene, glucagon / glycogen, refraction / reflection).

4

The error carried forward (ecf) principle should be applied, where appropriate. If an incorrect answer is subsequently used in a scientifically
correct way, the candidate should be awarded these subsequent marking points. Further guidance will be included in the mark scheme
where necessary and any exceptions to this general principle will be noted.

5

‘List rule’ guidance
For questions that require n responses (e.g. State two reasons …):






The response should be read as continuous prose, even when numbered answer spaces are provided.
Any response marked ignore in the mark scheme should not count towards n.
Incorrect responses should not be awarded credit but will still count towards n.
Read the entire response to check for any responses that contradict those that would otherwise be credited. Credit should not be
awarded for any responses that are contradicted within the rest of the response. Where two responses contradict one another, this
should be treated as a single incorrect response.
Non-contradictory responses after the first n responses may be ignored even if they include incorrect science.

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Cambridge IGCSE – Mark Scheme
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Calculation specific guidance
Correct answers to calculations should be given full credit even if there is no working or incorrect working, unless the question states ‘show
your working’.
For questions in which the number of significant figures required is not stated, credit should be awarded for correct answers when rounded
by the examiner to the number of significant figures given in the mark scheme. This may not apply to measured values.
For answers given in standard form (e.g. a  10n) in which the convention of restricting the value of the coefficient (a) to a value between 1
and 10 is not followed, credit may still be awarded if the answer can be converted to the answer given in the mark scheme.
Unless a separate mark is given for a unit, a missing or incorrect unit will normally mean that the final calculation mark is not awarded.
Exceptions to this general principle will be noted in the mark scheme.

7

Guidance for chemical equations
Multiples / fractions of coefficients used in chemical equations are acceptable unless stated otherwise in the mark scheme.
State symbols given in an equation should be ignored unless asked for in the question or stated otherwise in the mark scheme.

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Cambridge IGCSE – Mark Scheme
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Examples of how to apply the list rule
State three reasons … [3]

A

1 Correct



2 Correct



3 Wrong



B

1 Correct, Correct

(4 responses)

2 Correct



3 Wrong

ignore

C

1 Correct



(4 responses)

2 Correct, Wrong

, 

, 

3 Correct

ignore

D

1 Correct



(4 responses)

2 Correct, CON (of 2.)
3 Correct

© UCLES 2023

2

, (discount 2)

3

2

2



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E

1 Correct



(4 responses)

2 Correct



3 Correct, Wrong



F

1 Correct



(4 responses)

2 Correct



3 Correct
CON (of 3.)
1 Correct



(5 responses)

2 Correct




ignore
ignore

H

1 Correct



(4 responses)

2 Correct



3 CON (of 2.)
Correct
1 Correct



(4 responses)

2 Correct



© UCLES 2023

3

2

(discount 2)


I

3 Correct
CON (of 2.)

2


(discount 3)

G

3 Correct
Correct
CON (of 4.)

3

2


(discount 2)
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Question

Answer

May/June 2023
Marks

1(a)

N

1

1(b)

He

1

1(c)

I

1

1(d)

O

1

1(e)

Fe

1

1(f)

Al

1

Question

Answer

Marks

2(a)(i)

values between –100 °C and +58 °C (inclusive of these values)

1

2(a)(ii)

values between 3.20 and 10.0 (inclusive of these values

1

2(a)(iii)

gas

1

–10 °C is above the boiling point

1

2(b)(i)

displacement

1

2(b)(ii)

chlorine is more reactive than iodine / iodine is less reactive than chlorine

1

2(c)

configuration as 2,8,7

1

2(d)

damp litmus paper (1)

2

bleaches (1)

© UCLES 2023

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Question
3(a)

Answer

May/June 2023
Marks

oxygen

1

3(b)(i)

sewage / microbes

1

3(b)(ii)

deoxygenate (the water) / remove oxygen (from the water)

1

3(c)(i)

hydrogencarbonate

1

3(c)(ii)

ammonium

1

3(c)(iii)

0.44 (mg)

1

3(d)(i)

(substance that is) chemically combined with water

1

3(d)(ii)

heat

1

2(H2O) (1)

2

3(e)

H2 (1)

Question
4(a)

Answer
atom(s) with the same number of protons(1)

Marks
2

different numbers of neutrons (1)
4(b)

protons: 16 (1)

3

neutrons: 20 (1)
electrons: 18 (1)
4(c)(i)

© UCLES 2023

S + O2 on left horizontal line AND SO2 on right horizontal line

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