022].

2020/CAPE/MS 2015

CARTBBEAN EXAMINATTONS COUNCII,

CARIBBEAI{ ADVANCED PROFICIENCY EXAMINATION@

CHEMTSTRY

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MAY/.TUNE 2O].5

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Question 1

Specif,ic objectives: Module: 1 _ l.L, 2-5, 2.3, 2.4,

2.s

(a) (i) KC I'K xsi

cracking (1)
(ii ) vapour passed over cataTyst/
A1zO3/SiOz at 450 oC (1) 2
OR
Thermal Cracking high temperature (>600"C)
(iii) B: methane, cHa (1)
2
c: propene, CHsCH = CH2 (1)/ CH:cgcgz
NOBE: ft must be condensed foruriI.aei
are both gases and can be either girrea ttre products
(b) (i) o There is the unpairinq of (Ll 2sz electrons aCg or c
(or
tion o 2s2 to the orbi and
e.l-ectron en ters the empt P orbi-tal -
2
o The f, taLs
(1) orbitals sed ve4
(ii1 B.o*ine with propane in sunlight
Iaitiation: a1;Gr ----D Br. + Br. (1)
Ensure fish hook arrow is stroytr

Propagation tr EE
I
C-C
I l^,'--
"E ^ +
E c

E
I
EE
rt .'Ar

I
v
EEf,
tr-c-c-c.
tll + E:Br
ltl
EEE
(1)
BEX
E-c-c
tlt
{_gr.: ar
ltt -c
EEE
(11
IIEEI
* ltl+ +.Br
ttl
-C-C:Br
EEE
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stion 1 cont, d

. . frro etepa ate r€quLred in tlle ptopagatiolr stage,

steps are present and no tisn hook i..o* f..ri-' if-^ two

o If one of the two steps j.s missing

' and fish hook is
missing no marks allotted
Ieraiuation:
.Br + .Br Br3Br
E -..
EE EE EEEE
2a-g-
I
c
lt tt tttt
f, c-c-c
I
E
tt-c.
EE
-+
tt
-c-c
EE
ltlt -c- E

EEES
1)
E EE EEE
a-c I lt ttt
tt-c. 'i.st
c R-C-C-C-Br
-
E
I
EE
ltt
ETE
Any ONE to receive 1 narh
OR
bromine with propene (without sunlight)
EE
tt
E-c-c-c
E

+ Br:/\Br
I
E E
A]1 anrors shouJ.d be
fu.LI arrors and not FISE EOOR (1)

EE l
E-C
tt c
E

+ + :Br'
-C
I
E
(1)

EE E I
lt
E-c-c- I
c f, Br-
tt
EBT
+
+

(1)

E EEI
E
I
c
ttt
I
-c tt
-c -E
E Br Ba
(1)

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OR

UE
ll,/
H-C-C-c
B

+ Br Br (1)
1r
E
n

E E E +

I I I
E c c E + :Br-
I
-c I
+
E Br (1)

The two first steps can'be merfed with the appropriate arrow, one mark for
the direction of each arrow

UE E +

H-C-C
ll I
c E + Br- (1)
ll
H Br
+

u T E
I I I
I
E c c c B
I I I

E Br Br (1)

!,
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Ouestion 1 cont'd

KC T'K xs

(iii) Free radi.caL substitution

OR (1) 1
Electrophilic addition,
(c) (i) The reddish brown colour (1)of the bromine is 2
decolourisbd in sunlight (1) -
(ii) The purple colour (1) of the permanganate sol_ution is 2
immediately decolourised / pale pink(1)

Eotal 15 uarks 5 6 4

*
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Question 2

Specific objectives: l{odule: 2 - L-L, 2-2, 2-3, 2.A, 2'5

KC T'K xs
(a) (i) Accuracy

Reading burette at eye levef

Removal-of filter funnel after adding titrant to burette
Reading burette to 2 decimal places (1)
Eliminate any bubbles in bureEte tap
Do not blow out remaining liquid at the tip of the pipette
Overshooting the burette
AnY ONE
1
(ii) Precision:
Adding titrant drop by drop near the end point
Taking successive readings untj-l constant voh:rnes are
obtained
Taking successive readings until the volume does not dj-ffer
by more than 0.1cm3 (1)
Faulty calibration of instrument
If the student answ€trs in the positive or negatine, accept-
Arly oNE 1
(b) o High level of purity (1)
. Atmospheric stability (1)
. Large mofar mass (1)
. Reasonable solubility in titration (1)
. Absence of hydrate water (1)
o Cheap and readily avai-lable Any lIEo (2) 2

(c) (i) Graph: (Page 7)

Draw a curve, (1)
6 accurate points (1) 4
Best fit (2')
Accepted fit - 1 mark onIY
(ii) End point volume: 24-5 + 0-5 (1) 1

(iii) 2'o x 25
25 cm3 NaoH contain
1000
: 0.05 moles (1)
Give the mark for expression NOT the answer.
Moles NaoH: HC[: 1:1
Moles HCL : 0.05
24-5 cm3 HCt contaln 0-05 mol-es (1)
2
0-05x1000
1000 cm3 conEal-n (1)
24 -5
:2.04 M HCI
* Not Earkirrg for unit
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Question 2 cont'd

KC T'K xs
(d) 25 cm3 NaoH added to a polystvrene cup using a
pipette. (1)
(Sofrrtiot allowed standing for few minutes)and
temDerature noted- (1) 4
ffi acid added from burette, mixture
stirred and temperature noted. (1)
This is:repeated"until a total of 45 sr3 of acid
until the (1) temperature stablised'
"." "aa"a'or

Total 15 marks e 7 4

*
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r..)'iesEion 2 cont'd

.l:;..
LLt-
rp.!r
.*r. l.;.
'-F|-

+*
-l..-

-i_-

I
t
t
a
,.
&
E
u

-l
-f

j-
-i-;
I

32 '-1-r ti i Tl : i].1 i;
.,-:], l.:
.-l-l L- -r- r.J." .1,.1
I,
' ll -! : Ii ri.I.! i/{
.-LL il
!,rt
-l- t --- -r{+
-l+--i-
I
-+, (f) tor 2 ilfutbat llnor
'- rl-.- J -f-1- -;*{-F--i -ilt-ird (l) tor p.tot tG aooutet !tolut.)
--tst-;_ -rln-
'I "-! I ri
..r
(2, b..t llt Lbcr
-' l'l^- -1'1r'
:.f ffi
I il
.l
;- i i -T
.l
ll ,1 I L.
i.
l
i ,...-i +
f !-

---!- . i'f

-F i-'
li

I
ii+f;

33
tlfi
10 ls 30 30
volur of rcld rddod (crt)

*
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Question 3

Specifie Objectives: tfioduJ.e: 3 - L.2,7.!, 1.2, 1.3

KC UK xs
(a) Increased pressure/conc. of reactants (X KC)
Decreased temperaFure (1 KC, 3
usd of d catityst' (1 KcI : i

(b) (i) chatelier's Principle: if one or more factors that

rLe:
affect an equilibrium are chanqed, the position of 1
equiltbriurn shift-3 in the direction which opposes
the change- (1 XC)
(ii) . Low terperature (1 UK)
2
o ltigh pressure (1 tII()

(iii) o The sulfur trioxide is dissolved inLo conc. sulfuric

acid to form oleum (1 xS)
. The oleum j.s diluted with water to form conc. sulphuric Z

acid .(1 Iq)

(iv) o HzSOr(/) + Sog(S) -+H2S2or (1)) 2

o HzSzoz(|,) + Hzoot --+ 2Hzsoa(|,) 2

For each :eglll: B;+anced (1) + state .s1mbo1s (1)

If in b(iii) 'studditts"uied sulphuric acid o..r Qi fute sulphuric
acid, state slnnbol for sulphurj-c acj-d must'be ( aq) in part (iv)
(v) Safetyconsiderations
Reaction between SO: and vlater is highly exotherrnic
(1)
Clouds of sulfuric acid are produced. (1)
Sulfuric acid can cause burns Lo the skin and flesh. 3
(1)
sulfuric acid can cause blindness if it gets into the
eyes. (1)
Use of protective gear
Any THREE of. ttre aborTe, 3 x 1

i
I

Eotal 15 marks 4 6 5

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022L2O2O lCAPE /MS/2 O 1 s
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Question 4

Specific objeetives: Modulei L - 4-L, 4.2, 1.?, 4.4, 4.4, 4-5,.4-5

xc I'K xsi
(a) Addition polymerisdtiurr involves the linkinq of cne
type of monomer with double (1) or triple bonds' to
s ive Lhe pollmer as the roduct ( 1):

Condensation polymerj-sation invofves the linking of

two types of monomers oR monomeri wi th biilunctiona:.
two funct onal r (1) to give, thg
4
polymer and a small molecule such as water or
hyd,rogen chloride. (1)
Students must mention the tYPe of bon4- and the
amount of products for EACH tYPe of lrclymerization
to get ttre 4rks

(b) Carbohydrates/Polysaccharides (1)

Proteins (1)
Note: PoJ-yamides cannot be accepted here siace ttrey
include symttretic substances- Polysaccharides are
aII naturally occurring.
€.9-. glycogen
- cellulose 3

starch (1)
pecEin
albumin
keratin
collagen AITY oNE

(c) o o
ll il
DEO CE2CH2- Of, + nEO c --@- c OE
-
ethane':lr 2-dtol beazeDe-I, 4-
dicarboxylic acid
(1) (11
$ 4
o o
il il
o-cEzcB2-o- c
-@- c
(1)

+ ouzo (1)

Studeuts will be penal.ized for NOI insertiag ttre

'rf in ttre lrcIyner onIY.

&
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Question ,l cont'd

KC UK xs

(d)
The .,Jrink between the two monomers is
OE
ilr
-c-ll-
(1)oR
N
because one end of unit is and
I
f,
'c:
the other end is ll
o
E CE.
The remaining part of repeating
unit has (1).
lt' 1

-E-C-C-
ril
EO
E
and (U giving monomers:
r - cEr- c
I

I
o
cE-
I'
B--;tr-C-C-OE
,lll EO
(1)'
E
I
E-tr-cE--c-oE
'll 4

o (1)

If 'the breaking of C to N bond i.s shot^rn and the monomers

are cortect then the mark awarded is 3 marks- If the
breaking of'the-bbnd is not shown then the mark is two.
lfotal 15 aarks 7 I
OR

If the parts of the polymer are given (the pollmer has been split and the
both halves shown) ,then 1 mk each. The actual monomers shown for each part
of the polymer given wi'll r'eceive Lmk each- 4l'trCs
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Questign 5

ipecific Objectives: Modulei 2 - 8.7.t 8-2, 8.3, 8 -4, 8.5, 8-6

KC T'K xs
I

(a) Chromatography involves the separation of components

of a ruixture bet ween two Dhases. (1)
Involves the partitioninq of ts between a
stationarv phase and a mobile phase. (1)

Partitioning occurs because the gomponents of the 4

mixture wiII exp.erience different absorption forces

Have different soi-ubil-itY wi th the mobile phase. (1)

If student stetes o! iuPLies ttrat a uobiJ.e phase aDd a
stationary phase axists - 1Ek
(b) (i) The componen ts can be detected by a reagent calfed
a loca tinq agent or visualiz inq aqent (1) . This
will react with the component and ,!ryg}gg5! 2
compound. (1)
(j-i ) Rr = Distance moved bY solute
Distance moved by solvent (1) 1
If eguation is iupJ.ied give the uark
2.5 1
R. of = 0.2 (1)
' 13.5

t2.5 t-
R-ofR=-=0-9 (1)
' l-3.5

(iii) Rhasa eate ubilit l_n mobile (1)

than Q hasas yto torb onto
the stationarv Phase. (1) oR Q is more Polar so 2
1t is stronglY adsorbed on to the stationarY Phase
than R which is less Polar-
If student says Rr factor of Q and R differ because of
difference in solubilities and differ in ithe levels -of
adsorption onto the stationary phase -€!{EY lEIs
(c) Thin layer chromatograPhY:
Separates smafl amounts of compounds (1)
usla to separate (dyes, aniao acids, plant pignnents) (1)
Less useful if quantificatlon of large amount are 2
required. (1)
Cannot separate compounds of slmilar Rr values' (1)
Sauqlles can be removed fr,lrtL ariilysis' (1)
*
Use (1) + conrnent on usefuJ-ness (1)
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Question 5 cont'd
Specifie Objectirres: t{odul.ez 2 - 8.1, 8-2, 8.3, 8-4, 8.5, 9.6
KC t,K xs
(c) Column Chromatography:

Large anounts of material- can be separated and collected-

(1) 2
Large columns can be'u'sed'for purification- (1)
Can be used to prepare compounds. (1)
Fractions can be collected for'.analysis- 11)

Use (1) + comeat on;usefuJ.liess (1)

ltota1 15 narks 7 I

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::i.,rj
.-.?']
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.'(+
1,.i1

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Question 6

Specific Objectives: Module: 3 - 6-L, 6-4, 9-2, 3.3

tRc'' T'K xs
(a) CblorLae E1drogea
4' A
I

I
t I

concentrated
sodiurn
cbloride
solution
3tee1
fitaniu- cathode
anode

Sodiun
Diapbragu solutioD
cotltaEiEated
witb f,aCI
Must be conc sdiu[ chloride or brine
Anode i 2 C/-(aq) - 2e- Clz (S) (1 Kc)
Cathode: 2H* (aq)+ 2e- 4 Hz (S) (1 Kc)

DiagrarnpglY (1 Kc)
Diagran + 2 labe1s (2 Kc) 6
Diagran + 4 J.abels (3 Kc)
Diagram + 5 or Dore labe1s (4 Kc)

to) Health concern-Iink concern wirh its effect 1

Use of asbestos diaphrasm (LKC)

Asbestos deteriorates with use overtime' (t'E) 2
Dry asbestos fibres can be inhaled/ingested causing
respiratorY Problems - (Ix)
Asbestos is considered to be carcinogenic (UK)
Possible leakage of chlorine gas into the environment- 2(LK)
1 KC + anY IIKs

(,
,: "':: ,'

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Question 5 cont'd
KC I'K

(c) (i) Production of CFCs has decl-ined:

It was discovered in the Lg70,s that cFCs accelerates the
depletion of the ozone layer in the atmosphere' (1 ulc)
Destruction of the ozone Iayer allows harmful w radiation (1
3
UX) to reach the surface of the EarLh.
CFC's are broken down in stratosphere to g ive chlori-ne free
radicals which react with ozone to cause its conversion to
oxfi-n-(l tK)
(ii) Products of combustion of fossil fuels - Coz:

COz is a "greenhouse gas" - (1)

Increased concentration of Coz- contributes to the

greenhouse (1) effect i'e' qIobal warming'
3
Negative effect on the atmosphere through melting of
gficiers and ice-caps increase in sea leve1s' (x)

Decreases productivity of the land

SOzTCOTNOz emissions ].ead to acid rain
lltr€lmnEEofttreaborreorsirni].ar-3x1nark

Tota]. 15 uarks 7 I