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Cambridge .IGCSE™

CANDIDATE NAM!=

CENTRE NUMBER

CHEMISTRY

� Cambridge Assessment· • ·lnternatior,at Educ�t!on

CANDIDATE NUMBER

0620/42

Paper 4 Theory (Extended)

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 nam'6, centre number 1;1nd candidate. numb.er in the ·boxes af 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.• Ypu may use a calculator. . • You shoµld show.all y,ourworking .and use appropriate units.

INFORMATION • The-tot�I mark for this paper is 80.• The number of marks for each question or part q1,1estion is shown in brackets [· ].• The Periodic Table is printed in the question paper.

IB20 03_0620_ 42/2RP ©UCLES2020

This document has 12 pages. Blank pages are indicated.

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I IIIIII IIIII IIIII IIIII IIIII IIIII IIIII IIIII IIIII IIIII IIIII IIIII IIIII IIII IIII 2

1 Petroleum is a useful ·natural resource_

The diagram shows how petroleum can be separated into useful substances_

petroleum - =

�- refine

.� gas

�� gasoline fraction,

�-A

L . .,

�-keroiene fraction

L-diesel oil

L- fuel oil fraction

.. � � '"'''"''"' cl[ fracilo,

\ �B . •

• t

(a)' What is the name·ofthe separation probess"shown in the di§gra'r-li?

•

___ .f.?.JOt/Jp��------:rl�-@ ___ , ________ , _______________________ ,_:,, _____________________ , __________________ [2]

(b) Name the fractior, leaving at:

A ·-. _9flk,_d!,_w_, ----. -·---. ----·-·-. --------------·-------,_ ·-·--------------,_ ------__ ,:. __ ----_:_. ----·--------_, --_, ------,_ ·------------:

s __ _N_�-------------------------------------------------------------------:--------------------------------------------------------, :[2]

(c) Refine� gas is a mixture of hydrocarbons_

One refine� gas is butane, C4H10_

(i) Suggest the names of two other refine� gases_

____ J�,,-- .. .E�---------------------.. --------- and ---fMP�,,t_ .. ___ , _________ , ____ , ___ , ___ , _______ , __ [2]

(ii) Write the chemical equation for the,.complete combustion-of butane _

__ .. _(4_fl.Q. __ t.1:t��-------------�--W.tP_2 ___ ,_,_t ______ !�.l-2.cO.----·------------------------------------- 121(iii) Name the toxic gas produced py the incomplete combustion of. butane_

---�9Q:h ______ .M9n.o._��Af __________________ , ____________________________________________ , _____ , _______________ 11 1

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.(d). Gasoline and kerosene are both.fuels; They have different properties.

(i) Describe the differl:lnces in the properties given.

viscosity of !/le fuel .. V.it.W.P.t:fJa ... ,CY,(MNA. ..... � ... ,h.OW. .. 1.� ...... 0.., ........ . ,) .... �IM'l.tf ..... .c� .... §Jo.w.:i .. f�.°.�.:� .. � ... �� .... �� .. �� .. ��./ir.,c

flammability of the fuel ... T./:>. ...... hd..W ..... .i�.;·'· ... Q\.. .... f.0,eJ ... O!.\ ...... � .......... .... :�'J°Ql.hCQ .. , ... �, ........ ��, .•... f."-�.0.·N· ... � ... �l:).J ... f...��a,(,jr,)

. · �M �OM� [2]

(ii) What difference in the molecules of-gasoline and kerosene causes these differences inproperties?

.. 'i&� ..... t.m� ...... 1 ... � ..... �.9k-P.�kP� ... � .... l� .. f!:.::e. ...... [1J

olf6<-'1Jfr>.,l¢.i . ,,

(e) Hydrogen fuel cells can be used to power vehicles.

Write the word equation for the overall reaction. that takes .. pJace<in a ,hydrogen .fuel cell.

............. .2 .. H .�.,.tl<?.1 ..... , ....... ?. : ... 2.t\ '*·@ .............. ,., ....... :.: ........................... ,.. ...... r11

[Total: 13]

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• 0011434149304 •

I IIIIII IIIII IIIII IIIII IIIII IIIII IIIII IIIII IIIII IIIII IIIII IIIII IIIII IIII IIII 4 •

2 Aluminium is extracted from its ore. The ore is converted into pure aluminium oxide, which then undergoes electrolysis as shown.

+ power -�--...,-1 supply

anodes

+ ,l,cirolyte

�11· •

•••..:

molten aluminium

(a) (i) Name an ore of aluminium .

wires

cathode

.. �K, ........................................................ · ................ : ..................... : ................ [11

(ii) What is meant by the term electrolysis?

... uu:v.-i.o.�:t::i ...... "6 ..... �d ....... fu ...... �1i.®.:f.6.>.t .... � ... i.t;,.ti..c ................. .

... C®Y.f !l�� .... � .. Ji.lilAfMA. ... �N4 ... b>�.� .... (Y.LL.� ............ [2]

�"'"% �\,\.'C.-:� •. .

(b) Aluminium oxide has a melting point of about 2000 °G, but the electrolysis process operates atabout 900 °C.

(i) Name the compound added to aluminium oxide to reduce the operating temperature .

... �.oAil ....................................... : ....................................................................... [11

(ii) Suggest one benefit to the environment of reducing the operating temperature .

.... H!J!>. ... NM. ...... 0. ..... w.d: .... � ...... � ..... �%···�·····w..9!4rJ.. .......... .

... W: ....... � ....... C0.2.. ... � .... r.'JC>�d ...... !d: ... O:¥.IOc4. .................................... [1]

(iii) Write the ionic half-equation for the reaction taking place at:

the negative electrode (cathode) .l.fe�� .. t.'.h�� ......... !. ... f.(2.; ................................... .

the positive electrode (anode) .... ?..Q� .......... .!. .. .9..?.. . .! .. �� ...................................... ..• • -<.•.. ' • ,[4]

(iv) Explain why the anodes need frequent replacement.�

... TN ....... Mo?MA ...... Mt. .... m<Jd.f. .. 4-... oj.. .. �.1 .... w.k.'.cA ... 0. ..... ® ...... .

.. o.J./o.1iiap.r.. ... ef. ..... �n., .... :The ..... @!.WJJ.� ... � .. �� .. P.:!:-..Q��-·· 121o(w, /;v IN Jv:<tv �F".,J:tVJl • � /tJ1'v/¥1.tl CO2 °""d tp.,_ cwx/.e yW),t� OJ-.U�-

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l i

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1 j Q 'l

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I

(c) Aluminium oxide reacts with acids and with alkalis.

(i) What term is used to describe an oxide that reacts with .aeids and-with alkalis? ·

.... CV/'.lf.ho� ...................................................... · ............. : ........................... , ........ [11

(ii) Aluminium oxide reacts with dilute sulfuric acid to form a salt.

State the name and write the formula of the salt formed.

·name ...... �J:U.� .... 4"� ............................................................ ,., ................formula .. A'lkO. .3 .... ;·f�;. i��.J-J:2:_ ??.�.L{: ....... 6. iii_: 2.:f.! 1{$ Q. 0.}if I:): k1:2lG?.: ; ..... , .":: ''-

. • [2] I ;!, J • I ' ,

'J • '

(iii) Aluminium oxide reacts with dilute sodium hydroxide to fprm a salt and·one other product.' ....

Name the other profluct.

....... W.��b. ...................................................................................... : ........................ [1]

(iv) Aluminium hydroxide, AZ(OH)s, decomposes when heatE1d ·to form aluminium oxide andwafer.

··

' \Write the chemical equation for this reaction.·

... � ....... 1f.lt. .. .l.9..t!.)3 ........ �.� ..... >. ... :Afz.03 ...... ± .. �./:h..f?. ............. , .... [2]

(v) Suggest the names of two other aluminium compounds that.decompose when heated toform aluminium oxide.

.. A�WY.l .... [email protected] ................................................................................. .

.A.��.� ..... c.Mki.oti ................................................................................ [21

-tl+,-03 +3H :;2.. CJ

-2-J1---1. -t&-f:1-4. . �? r c

/1 i.i_:J i +

2- fl- L

60 f;H

( : �

-.J \.. l\.

[Total: 19]

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I llllll lllll lllll lllll lllll lllll lllll lllll lllll lllll lllll 11111 11111 11111111 6 •

3 The Periodic Table is a method of classifying elements.

(a) Identify the element which is in Group VI and Period 4 .

. . . . . JR,, ... /.. A-de.ii.\N.m.............................................................. . . . . . . . . . ... . . .. . . . . . .. .. . . . . . . . .. . . . [ 1 ]

(b) Calcium is in Group II and chlorine is in Group VII of the Periodic Table.

Explain, in terms of number of outer shell electrons and electron transfer, how calcium atomsand chlorine atoms form ions. Give the formulae of the ions formed .

... A.n ... !� ..... lt.R.n<A ... w.Ml. .. !!i .. 60.� ... � .. C� ... IA ... � .. mit� ... � .

. /,w ... 2. ... �� .. iJt. .. @ ... � .... l'!.#.!, .. w.!:ArA.d:: .. � .... d..9.0.ri4. .... tz> ......... . .-.AU 'ti• wk. _/ ' {h1a ' ' • .ku.oVM. .... /fil ... ,,,..,,�.'. "'>·;r ..... CkJfJA°<J,O.. ..... t.-Lm.. �-......... �r.g, ... -�·. !IJ. ... q(J-9.� .7. ...... .

.. � .... � .. ONc ... � ... o{.C! .. � ... � ... /.�.<>.o.., .. f1.4..!£,_ .... 1 .. Cf?k::�

.@.?.� .... i�.� ..... v.owk .. � .... 2 ..... �� ..... oJ..<?!Y.0..-... P.0, .... � ..... .

. � ... 0;!.k. .... �.'. .. 0.l:fr?.� ... .l,!'.� .... mi.4..f:-1 ..... �'.Q.� ........................... . ...... C<t". ... ±1cf=?': .. C.P.!fl.i.: ... .C.O:.�t.�.=?..� .... lCJ...�=:'?..G2t.2�: ..... 1s1

(c) Group V chlorides are covalent molecules. The boiling points of some Group V chlorides areshown.

chloride boiling point/°C NCl3 71 PC/

3

AsC13

130 SbCl

3 283

.QL Suggest the approximate boiling point of PC/3 .

......... 00 .. � ............ A.6. .. �{ ............................................................................. 111

(ii) Explain the trend in boiling points in terms of attractive forces between particles .

.... l!.1-. ..... �.�i.� .... r..�J.� ... #.!f¥..<M ..... � .... � ..... � .. �P.'l:�.t ....

.. -��M!k ... 1, .. . . 4AAf.1l. Q� ... !kt .Q\to.! .... �-.. � .. MrJ. v.<. .... 0.!?. w.t.1....................... [2]

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• 0011434149307 *

I IIIIII IIIII IIIII IIIII IIIII IIIII IIIII IIIII IIIII IIIII IIIII IIIII IIIII IIII IIII 7 •

(iii) Complete the dot-and-cross diagram to show the electron arrangement in a molecule ofPCl3.

Show outer electrons only.

[3]

(d) PCl3 reacts with chlorine, Cl2, to form PCl5. This reaction is exothermic and reaches anequilibrium.

(i) Describe two features of an equilibrium .

... 9.t.iM ..... 1-... .;P..t.wJ.MfA ....... N� ..... � .... �� ..... P.?. ... � ............... .

... r1, ..... � .... �.� ....... fhR.�.tl.: ... �.�n ..... cf .. (, .. �O,MQ.l

.... M:\ ... ��.� .... )>.{�c.4 .... u. ... l� .. fu ... Co.�.b¢.��:-'.\ ... M, ... N�. [2]

�04, (ii) State the effect, if any, on the position of this equilibrium when the following changes are

made. Explain your answers.

temperature �s increased ... iJ.. ... w.4.!: .... l'J'Y)l/:-:f:.. .... -/P.. ..... � ...... f#..� .. krit .......

;J . � ft_ • • . . I;_ 9UJUL' ..... � ............ � ........ � .... �.� ...... 11!'!1. ................. � ....................................... .

pressure is increased .... � .... J.. ... � ..... �". ... �P.� ... �9.� ....... .. ..... � .... � ....... � ...... #..0.-.... �.:.� ..... M�f4 ... �.� ... �� .. �(J.lf

[4]

(iii) Explain, in terms of particles, what happens to the rate of the forward reaction when thereaction mixture is heated .

... � .... p.�.� ...... ��-····0.1.o.� ... � ... �� ..... �� ... ,toitP.:,.� ............

... l;@.., ..... � .. Q:f .... ��o/\� ...... �.Q.� ...... 4/JP.i.� ..... � ..... � ..... . .. a...A .... M .... <M??�.�-� .... ?.M.�.� ..... � ... � .... p:.ics.� ............. .

.. ktot:-: ... & ... � .... N.ef. ... �.� .... rxJ; ... P.:h.f.b!J.� .... � ............. .

.. ffe. .......... pfY1.<.<h ..... Jew1.l!l.\ ...... lcw.iw.� .... ��.'(I ........................ [3J

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(e) PC15 reacts with lithium fluoride, LiF, to form LiPF6.

PC15 + 6LiF --+ LiPF6 + 5LiC1

Calculate the mass of LiF need�d to form 3.04g of pPF6 using the following steps.

• Calculate the number of moles·ofLiPF6 formed.[M,: LiPF6, 152] iVlD»-> :: r,-,oleA ,

MO))b 3. ou l'VJV'

M'r 15'J.. moil»:, 0 . o '2.

• Deduce the number of moles of LiF needed.

().()2'>tb

• Calculate the mass ofLiF needed.'2-b

..- -

o. 1'2..

(f) Lithium fluoride _has ionic bonding.

(i) What is an ionic bond?

number of moles= ...... q.:.0.2 ......... .

number of moles= ... 0.., .. 1.2 ............ .

mass= .... 2 .. Lb .. ,Jl ..... g[3]

, ... .fh.b.o�ti. .. M.� .. , .. Q: .... �� ...... � ... O,. .... � .. f'l9.� ... rhi/PJ ............ .

···��;,f!:��11�'0.�: .. (..:&.�.0:b ............. [2]

(ii) Give two physical·properties qf ionic compounds. ,

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.. � ... � ..... �� ... 150.�!'.lb'.d..;..//.IO.C. .. �.� .. , ... � ............. .

... !?A..l., .... �ft..� .... M .... � .. f!r:',.o.� ..... w .. .la!'.0 ... 0.._..fl�.Nr).��········ [21C�,{, :U� � lb NF-' &tAfi fJ.-.t u,,.1,.o,lt b<1tcLfu

[Total: 28]>;,�.

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I llllll lllll lllll lllll lllll lllll lllll lllll lllll lllll lllll 11111 11111 1111 1111 4 Iron is a typical transition element.

Iron: • acts as a catalyst • forms coloured compounds • has more than one oxidation state.

9 •

(a) Name one major industrial process that uses iron as a catalyst and name the product made inthis process.

process .... .H� .. p.!.1,0..@. ................................................................................................... .

product made ... � ..... �.M.� ............................................................................. , .... ..

. [2]

(b) When aqueous· sodium hydroxi<;le is added to aqueous· iron(Il) sulfate, a precipitate forms.

(i) What colour is this precipitate?

····�···································································;······'··········································· [1]

(ii) -

Write the ionic equation for this reaction. lntjlude state symbols.

1.�.0.-.P..�Wl� .. .fe_ ... {?.�:�J� .... .C0W.). ....... ?..I.N.iA-.. �.0..4.Cl).°t .. Ff.2.Pi,i:.H.� fii)

\/·'··

·!::J .... . . . .c.Cs)

(c) lron(Il) sulfate can be converted to iron(III) su:fate by botassium manganate(VII) at room. temperature. . '

(i) What is the role of pota�sium manganate(VII) in this reactio';i?

CWM'n ,., ",,,.1: ···�············i······�!.Y! ........................... , .................................................................. [1]

(ii) What condition must be .used for.this reaction-to occur? .

...... � .. �::�4: .. '. .. '. .. f. ... !!.!.'it. ... .Q�Wf.' ..... , ................... : ................... ,, ............. [1]

(iii) In terms of electron transfer, what happens to the iron(II) ions in this reaction?

.. lt .. �A ....... f?!N,. ..... �.an. .......................................................................... 111

(iv) State the colour change seen during this reaction.

from purple to ... w.Jo� ....................................................................................... [1]

(d) Deduce the charge on the iron ion in each of these compounds.

p,3-1- + F -::: F"e F FeF3

•...............••....•........ , ... Ss •••.••.•.••••••• ,1 .......... : ....... -3 ............................................................ .

Fe.'2.i

Fe(N03)s ................................................................................................................................... .

[21

[Total: 12]

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5 There are two types of polymers.

(a) Addition polymers are made from many identical small units.

(i) What is the term used to describe these small units?

•

.... M.9.hP..� .......................................................................................................... [11

(ii) A section of an addition polymer is shown.

H CH3

H CH3

H CH3

I I I I I I -c-c-c-c-c-c-

1 I I I I I H CH

3 H CH

3 H CH

3

Draw the structure of the small unit used to make this addition polymer.

Show all of the atoms and all of the bonds.

CJ\ \-\ 13

l

C -C I

(b) Polyamides are condensation polymers.

n

What does the term condensation mean when used to describe this type of polymer?

[2]

...... � ..... �qcfMu ....... w..o:!.ih ...... � ....... f9.4��······································ [1]

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(c) A polyamide can be made from two different molecules.

A simplified structure of octanedioic acid is shown.

0 0

II II H-0-C�C-O-H

A simplified structure of 1,6-diaminohexane is shown.

H H

l___r-,_

1 N---i_____r-N I I H H

•

(i) Complete the diagram to show a section of polyamide manufactured from octanedioic acidand 1,6-diaminohexane. Include all of the atoms and all of the bonds in the linkages.

--

J I ,I II

rv -c=J � - C.-1 __ t-C - t'

(ii) State the name of a synthetic polyamide .

\I I

J - C.-j ___ t- G -

[3]

..... Ni.<?.� .................................................................................................................... r11

[Total: 8]

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To avo,d the issue of disclosure of answer-related informat10n to candidates, all copyright acknowledgements are reproduced online 1n the Cambridge Assessment lntemabonal Educabon Copyright Acknowledgements Booklet This Is produced for each series of exammallons and 1s freely available to download at www cambndge1ntematlonal.org after the live exam1nabon senes

Cambridge Assessment lnternabonal Education Is part of the Cambndge Assessment Group. Cambridge Assessment is the brand name of the University of Cambndge Local Exam,naoons Syndicate (UCLES), which itself 1s a department of the Umversrty of Cambndge.

l-£.ucLES 2020 0620/42/ _J

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L

The Periodic Table of Elements

Group

I II

1

H

Key hydrogen

1

3 4 atomic number

Li Be atomic symbol lilh!um borylllum name

7 9 relative atomic mass

11 12

Na Mg sodium magnostum

23 24 '

19 20 21 22 23 24 25 26 27 28 29

K Ca Sc Ti V Cr Mn Fe Co Ni Cu potassium calcium scandium Utunlum vanadium chromium manganoso lro, cobalt nlckol coppor

:39 40 45 48 51 52 55 56 59 59 64

37 38 39 40 41 42 43 44 45 46 47

Rb Sr y Zr Nb Mo Tc Ru Rh Pd Ag rub!dJum strontium yllrlum zirconium niobium motybdonum technotrum rulhonlum rhodium palladium sliver

85 88 89 91 93 96 - 101 103 106 108

55 56 57-71 72 73 74 75 76 n 78 79

Cs Ba lanlhnnolds Hf Ta w Re Os Ir Pt Au caesium tmrlum hafnium tan!a!um t1mgston rhenium osm!um Iridium ·platinum gold

133 137 178 181 184 186 190 192 195 197

87 BB 89-103 104 105 106 107 108 109 110 111

Fr Ra 11clilolds Rf Db Sg Bh Hs Mt Ds Rg francium radium ruthoffordlum dubnlum soaborglum bohrlum hasslum moitnorlum darmstadtlum roentgenlum

- - - - - - - - - -

57 58 59 60 61 62 63 64 65

lanthanoids La Ce Pr Nd Pm Sm Eu Gd Tb lanthanum eorium praseodymium noodymlum promethium samarium europium gadolln!um terbium

139 140 141 144 - 150 '152 157 159

89 90 91 92 93 94 95 96 97

actinoids Ac Th Pa u Np Pu Am Cm Bk act!nlum thortum protact!nlum uranium noptunlum ptu!o_nlum americium curium berkoln.Jm

- 232 231 238 - - - - -

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

Ill IV V

5 6 7

B C N boron �""'' nitrogen

11 12 14

13 14 15

AZ Si p a!umlnlum sllicon phosphorus

27 28 31

30 31 32 33

Zn Ga Ge As "" gamum germanium arson le

65 70 73 75

48 49 50 51

Cd In Sn Sb cadmium indium "' antimony

112 115 119 122

BO 81 82 83

Hg Tl Pb Bi mercu,y thallium lead bismuth

201 204 207 209

112 114

Cn Fl copom!clum flerov1um

- -

66 67 68 69

Dy Ho Er Tm dysprosium holmium erbium thuln.Jm

163 165 167 169

98 99 100 101

Cf Es Fm Md caldOmtum einsteinium fermium mendelevium

- - - -

VI VII

8 9

0 F oxygen l!llorino

16 19

16 17

s CZ sulfur ch!orino

32 35.5

34 35

Se Br se!enlum bmmino

79 80

52 53

Te I tellurium Iodine

128 127

84 85

Po At polonlum astaUno

- -

116

Lv llvormorium

-

70 71

Yb Lu ytterbium lutetium

173 175

102 103

No Lr nobefium lawrencium

- -

VIII

2

He hol1um

4

10

Ne neon

20

18

Ar argon

40

36

Kr krypton

64

54

Xe xenon

131

86

Rn radon -

---= -

=o !!!!!!!!!!!!!! 0

�::: =.i,. -"'

_:::_,. -�= "'

!!!!!!!!!!!!!! •

==--

= = = -

....

N

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