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CHEMISTRY 0620/42
Paper 4 Theory (Extended) February/March 2020
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.
IB20 03_0620_42/2RP© UCLES 2020 [Turn over
This document has 12 pages. Blank pages are indicated.
Cambridge IGCSE™
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1 Petroleum is a useful natural resource.
The diagram shows how petroleum can be separated into useful substances.
kerosene fraction
A
gasoline fraction
refinery gas
diesel oil
fuel oil fraction
petroleum
lubricating oil fraction
B
(a) What is the name of the separation process shown in the diagram?
.............................................................................................................................................. [2]
(b) Name the fraction leaving at:
A ................................................................................................................................................
B ................................................................................................................................................ [2]
(c) Refinerygasisamixtureofhydrocarbons.
Onerefinerygasisbutane,C4H10.
(i) Suggest the names of twootherrefinerygases.
............................................................... and .............................................................. [2]
(ii) Write the chemical equation for the complete combustion of butane.
....................................................................................................................................... [2]
(iii) Namethetoxicgasproducedbytheincompletecombustionofbutane.
....................................................................................................................................... [1]
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(d) Gasolineandkerosenearebothfuels.Theyhavedifferentproperties.
(i) Describe the differences in the properties given.
viscosityofthefuel .............................................................................................................
.............................................................................................................................................
flammabilityofthefuel ........................................................................................................
............................................................................................................................................. [2]
(ii) What difference in the molecules of gasoline and kerosene causes these differences in properties?
....................................................................................................................................... [1]
(e) Hydrogenfuelcellscanbeusedtopowervehicles.
Writethewordequationfortheoverallreactionthattakesplaceinahydrogenfuelcell.
.............................................................................................................................................. [1]
[Total: 13]
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2 Aluminiumisextractedfromitsore.Theoreisconvertedintopurealuminiumoxide,whichthenundergoeselectrolysisasshown.
+ +
+ –
anodes
powersupply
electrolyte
molten aluminium
wires
cathode
(a) (i) Name an ore of aluminium.
....................................................................................................................................... [1]
(ii) Whatismeantbythetermelectrolysis?
.............................................................................................................................................
....................................................................................................................................... [2]
(b) Aluminiumoxidehasameltingpointofabout2000°C,buttheelectrolysisprocessoperatesatabout 900 °C.
(i) Namethecompoundaddedtoaluminiumoxidetoreducetheoperatingtemperature.
....................................................................................................................................... [1]
(ii) Suggest onebenefittotheenvironmentofreducingtheoperatingtemperature.
.............................................................................................................................................
....................................................................................................................................... [1]
(iii) Write the ionic half-equation for the reaction taking place at:
the negative electrode (cathode) ........................................................................................
the positive electrode (anode) ............................................................................................ [4]
(iv) Explainwhytheanodesneedfrequentreplacement.
.............................................................................................................................................
........................................................................................................................................ [2]
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(c) Aluminiumoxidereactswithacidsandwithalkalis.
(i) Whattermisusedtodescribeanoxidethatreactswithacidsandwithalkalis?
....................................................................................................................................... [1]
(ii) Aluminiumoxidereactswithdilutesulfuricacidtoformasalt.
State the name and write the formula of the salt formed.
name ...................................................................................................................................
formula ................................................................................................................................ [2]
(iii) Aluminiumoxidereactswithdilutesodiumhydroxidetoformasaltandoneotherproduct.
Name the other product.
....................................................................................................................................... [1]
(iv) Aluminiumhydroxide,Al (OH)3,decomposeswhenheatedtoformaluminiumoxideandwater.
Write the chemical equation for this reaction.
....................................................................................................................................... [2]
(v) Suggest the names of two other aluminium compounds that decompose when heated to formaluminiumoxide.
.............................................................................................................................................
....................................................................................................................................... [2]
[Total: 19]
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3 ThePeriodicTableisamethodofclassifyingelements.
(a) IdentifytheelementwhichisinGroupVIandPeriod4.
.............................................................................................................................................. [1]
(b) CalciumisinGroupIIandchlorineisinGroupVIIofthePeriodicTable.
Explain,intermsofnumberofoutershellelectronsandelectrontransfer,howcalciumatomsand chlorine atoms form ions. Give the formulae of the ions formed.
....................................................................................................................................................
....................................................................................................................................................
....................................................................................................................................................
....................................................................................................................................................
....................................................................................................................................................
....................................................................................................................................................
.............................................................................................................................................. [5]
(c) GroupVchloridesarecovalentmolecules.TheboilingpointsofsomeGroupVchloridesareshown.
chloride boiling point / °C
NCl 3 71
PCl 3AsCl 3 130
SbCl 3 283
(i) SuggesttheapproximateboilingpointofPCl 3.
....................................................................................................................................... [1]
(ii) Explainthetrendinboilingpointsintermsofattractiveforcesbetweenparticles.
.............................................................................................................................................
....................................................................................................................................... [2]
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(iii) Completethedot-and-crossdiagramtoshowtheelectronarrangementinamoleculeofPCl 3.
Showouterelectronsonly.
P
Cl
ClCl
[3]
(d) PCl 3 reacts with chlorine, Cl 2, to form PCl 5. This reaction is exothermic and reaches anequilibrium.
PCl 3(g)+Cl 2(g) PCl 5(g)
(i) Describe two features of an equilibrium.
.............................................................................................................................................
.............................................................................................................................................
....................................................................................................................................... [2]
(ii) Statetheeffect,ifany,onthepositionofthisequilibriumwhenthefollowingchangesaremade.
Explainyouranswers.
temperature is increased ....................................................................................................
.............................................................................................................................................
pressure is increased .........................................................................................................
............................................................................................................................................. [4]
(iii) Explain,intermsofparticles,whathappenstotherateoftheforwardreactionwhenthereactionmixtureisheated.
.............................................................................................................................................
.............................................................................................................................................
.............................................................................................................................................
.............................................................................................................................................
....................................................................................................................................... [3]
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(e) PCl 5reactswithlithiumfluoride,LiF,toformLiPF6.
PCl 5+6LiF→LiPF6+5LiCl
CalculatethemassofLiFneededtoform3.04gofLiPF6 using the following steps.
● CalculatethenumberofmolesofLiPF6 formed. [Mr:LiPF6,152]
number of moles = ..............................
● DeducethenumberofmolesofLiFneeded.
number of moles = ..............................
● CalculatethemassofLiFneeded.
mass = .............................. g [3]
(f) Lithiumfluoridehasionicbonding.
(i) What is an ionic bond?
.............................................................................................................................................
....................................................................................................................................... [2]
(ii) Give twophysicalpropertiesofioniccompounds.
.............................................................................................................................................
....................................................................................................................................... [2]
[Total: 28]
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4 Ironisatypicaltransitionelement.
Iron: ● actsasacatalyst ● forms coloured compounds ● hasmorethanoneoxidationstate.
(a) Name onemajorindustrialprocessthatusesironasacatalystandnametheproductmadeinthis process.
process ......................................................................................................................................
product made ............................................................................................................................. [2]
(b) Whenaqueoussodiumhydroxideisaddedtoaqueousiron(II)sulfate,aprecipitateforms.
(i) What colour is this precipitate?
....................................................................................................................................... [1]
(ii) Writetheionicequationforthisreaction.Includestatesymbols.
....................................................................................................................................... [3]
(c) Iron(II) sulfate can be converted to iron(III) sulfatebypotassiummanganate(VII) at room temperature.
(i) What is the role of potassium manganate(VII) in this reaction?
....................................................................................................................................... [1]
(ii) What condition must be used for this reaction to occur?
....................................................................................................................................... [1]
(iii) Intermsofelectrontransfer,whathappenstotheiron(II) ions in this reaction?
....................................................................................................................................... [1]
(iv) State the colour change seen during this reaction.
from purple to ............................................................................................................... [1]
(d) Deduce the charge on the iron ion in each of these compounds.
FeF3 ...........................................................................................................................................
Fe(NO3)3 .................................................................................................................................... [2]
[Total: 12]
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5 Therearetwotypesofpolymers.
(a) Additionpolymersaremadefrommanyidenticalsmallunits.
(i) What is the term used to describe these small units?
....................................................................................................................................... [1]
(ii) Asectionofanadditionpolymerisshown.
C
H
H
C
CH3
CH3
C
H
H
C
CH3
CH3
C
H
H
C
CH3
CH3
Drawthestructureofthesmallunitusedtomakethisadditionpolymer.
Show all of the atoms and all of the bonds.
[2]
(b) Polyamidesarecondensationpolymers.
What does the term condensationmeanwhenusedtodescribethistypeofpolymer?
.............................................................................................................................................. [1]
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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 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.
(c) Apolyamidecanbemadefromtwodifferentmolecules.
Asimplifiedstructureofoctanedioicacidisshown.
C C
OO
O O HH
Asimplifiedstructureof1,6-diaminohexaneisshown.
N N
HH
HH
(i) Completethediagramtoshowasectionofpolyamidemanufacturedfromoctanedioicacidand1,6-diaminohexane.Includealloftheatomsandallofthebondsinthelinkages.
[3]
(ii) Statethenameofasyntheticpolyamide.
....................................................................................................................................... [1]
[Total: 8]
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Gro
up
The
Perio
dic
Tabl
e of
Ele
men
ts
1 Hhy
drog
en1
2 He
heliu
m4
III
IIIIV
VV
IV
IIV
III
3 Lilit
hium 7
4 Be
bery
llium
9
atom
ic n
umbe
r
atom
ic s
ymbo
l
Key
nam
ere
lativ
e at
omic
mas
s
11 Na
sodi
um23
12 Mg
mag
nesi
um24
19 Kpo
tass
ium
39
20 Ca
calc
ium
40
37 Rb
rubi
dium
85
38 Sr
stro
ntiu
m88
55 Cs
caes
ium
133
56 Ba
bariu
m13
7
87 Frfra
nciu
m–
88 Ra
radi
um –
5 B boro
n11 13 Al
alum
iniu
m27 31 Ga
gallium70 49 In indium
115
81 Tlthallium
204
6 Ccarbon
12 14 Si
silicon
28 32 Ge
germanium
73 50 Sn tin 119
82 Pb
lead207
22 Tititanium
48 40 Zrzirconium
91 72 Hf
hafnium
178
104
Rf
rutherfordium
–
23 Vvanadium
51 41 Nb
niobium
93 73 Tatantalum
181
105
Db
dubnium
–
24 Cr
chromium
52 42 Mo
molybdenum
96 74 Wtungsten
184
106
Sg
seaborgium
–
25 Mn
manganese
55 43 Tctechnetium
– 75 Re
rhenium
186
107
Bh
bohrium
–
26 Fe iron
56 44 Ru
ruthenium
101
76 Os
osmium
190
108
Hs
hassium
–
27 Co
cobalt
59 45 Rh
rhodium
103
77 Iriridium
192
109
Mt
meitnerium
–
28 Ni
nickel
59 46 Pd
palladium
106
78 Pt
platinum
195
110
Ds
darmstadtium
–
29 Cu
copper
64 47 Ag
silver
108
79 Au
gold
197
111
Rg
roentgenium
–
30 Zn zinc 65 48 Cd
cadmium
112
80 Hg
mercury
201
112
Cn
copernicium
–
114 Fl
flerovium
–
116
Lvlivermorium
–
7 Nnitrogen
14 15 Pphosphorus
31 33 As
arsenic
75 51 Sb
antimony
122
83 Bi
bismuth
209
8 Ooxygen
16 16 S sulfur
32 34 Se
selenium
79 52 Tetellurium
128
84 Po
polo
nium
–
9 Fflu
orin
e19 17 Cl
chlo
rine
35.5
35 Br
brom
ine
80 53 Iio
dine
127
85 At
asta
tine
–
10 Ne
neon 20 18 Ar
argo
n40 36 Kr
kryp
ton
84 54 Xe
xeno
n13
1
86 Rn
rado
n–
21 Sc
scan
dium
45 39 Yyt
trium 89
57–7
1la
ntha
noid
s
89–1
03ac
tinoi
ds
57 Lala
ntha
num
139
89 Ac
lant
hano
ids
actin
oids
The
volu
me
of o
ne m
ole
of a
ny g
as is
24
dm3 a
t roo
m te
mpe
ratu
re a
nd p
ress
ure
(r.t.p
.).
actin
ium
–
58 Ce
ceriu
m140
90 Th thorium
232
59 Pr
praseodymium
141
91 Pa
protactinium
231
60 Nd
neodymium
144
92 Uuranium
238
61 Pm
promethium
– 93 Np
neptunium
–
62 Sm
samarium
150
94 Pu
plutonium
–
63 Eu
europium
152
95 Am
americium
–
64 Gd
gadolinium
157
96 Cm
curium
–
65 Tb terbium
159
97 Bk
berkelium
–
66 Dy
dysprosium
163
98 Cf
californium
–
67 Ho
holmium
165
99 Es
einsteinium
–
68 Er
erbium
167
100
Fm fermium
–
69 Tm thulium
169
101
Md
mendelevium
–
70 Yb
ytterbium
173
102
No
nobelium
–
71 Lu lutetium
175
103 Lr
lawrencium
–
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