142261 mark scheme unit f334 chemistry of materials january
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mark scheme, not paperTRANSCRIPT
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5/28/2018 142261 Mark Scheme Unit f334 Chemistry of Materials January
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Oxford Cambridge and RSA Examinations
GCE
Chemistr B SaltersAdvanced GCE
Unit F334: Chemistry of Materials
Mark Scheme for January 2013
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This mark scheme is published as an aid to teachers and students, to indicate the requirementsof the examination. It shows the basis on which marks were awarded by examiners. It does notindicate the details of the discussions which took place at an examiners meeting before markingcommenced.
All examiners are instructed that alternative correct answers and unexpected approaches in
candidates scripts must be given marks that fairly reflect the relevant knowledge and skillsdemonstrated.
Mark schemes should be read in conjunction with the published question papers and the reporton the examination.
OCR will not enter into any discussion or correspondence in connection with this mark scheme.
OCR 2013
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5/28/2018 142261 Mark Scheme Unit f334 Chemistry of Materials January
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F334 Mark Scheme
1
Annotat ions used in the detailed Mark Scheme (to include abbreviations and subject-specific conventions).
Annotat ion Meaning
/ alternative and acceptable answers for the same marking point
separates marking points
not answers which are not worthy of credit and which will CON a correct answer
ignore statements which are irrelevant and will NOT CON a correct answer
allow answers that can be accepted
( ) words which are not essential to gain credit
__ underlined words must be present in answer to score a mark
ecf error carried forward
AW alternative wording (replaces the old or words to that effect)
ora or reverse argument
Annotat ions used in scoris:
Annotat ion Meaning
correct response
incorrect response
benefit of the doubt
benefit of the doubt notgiven
error carried forward
information omitted
Ignore
Reject
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F334 Mark Scheme
2
Question Answer Marks
1 (a) (i)
C
C N
O
H2CO CH2
H2C CH2
H2C CH2
N
H
H
all correct 2 marks amide link only
2 ALLOW
any correc
mixtures o
CONH
Cs and Hs
IGNOREbrackets
(ii) CONH circled 1 ALLOWadjacent
(iii) 1,6-diamino hexane ORhexane -1,6-diamine
2 If butaneALLOWIGNORE commasALLOW 1,6-hexa
(b) (i)
HO
C
CH2
CH2
CH2
CH2
CH2
NH2
O
1 ALLOWany form
ALLOWcyclic am
N
O
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5/28/2018 142261 Mark Scheme Unit f334 Chemistry of Materials January
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F334 Mark Scheme
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Question Answer Marks
(ii) condensationANDwater is eliminated/formed/lost
IFcyclic amide in 1b(i) THENaddition AND hydrolysis (of ring) /water added
1 addition or additALLOWsmall moany other named s
(c) (i) (polymer) chains/molecules are (highly) ordered/alignedAW 1 ALLOW labelleddchains by using pa
AWmeans other egstacked closely aarranged regularl
(ii)
PPA chainsareclosertogether ORA
so intermolecular bondsin PPA will be strongerORmore hydrogen bonds in PPAORmore intermolecular bonds in PPA ORA
more energy/heatwill be required tobreak the intermolecular bondsORmelt the polymer OR allowchains to move over each other ORA
3 AS ALWAYSintewith intermolecula
NOTmore areas otogether NOTjustNOTEALL 3 mark
ALLOWany nam
NOT higher temp
(iii) cold-drawing 1 NOTco-polymerisIGNOREnecking
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5/28/2018 142261 Mark Scheme Unit f334 Chemistry of Materials January
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F334 Mark Scheme
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Question Answer Marks
(d) (i) 1. elimination 2. addition 3. addition
3IGNOREnucleop
(ii) can be used in step 3AW 1 NOT step 2
ALLOW can be sol
can be use
can be rec
(e) acidified dichromate 1 IGNORE
metal catio
name of ac
wrong form
oxidation s
ALLOWH2SO4/HDO NOT ALLOW
Total 17
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5/28/2018 142261 Mark Scheme Unit f334 Chemistry of Materials January
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F334 Mark Scheme
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Question Answer Marks
2 (a)COOH / carboxyl / carboxylic acid group is a proton/H+donor / loses H+
2 correct equation sALLOWgives H+
Mark separately
(b) (i) CH2OHCOOH + NaOH CH2OHCOONa + H2O 1 ALLOW
CH2OHCOONa+
Na+ CH2OHCOO
IGNOREstate symNOTCH2OHNaC
(ii) 1. moles of NaOHused in titration= 16.00/1000 x 0.250= 0.00400
6 There are severalafter point 2, the the concentration
If final answer isticks where the m
2.ALLOWby imp
The marks are awboldORthe correworking (but no mis wrong)
4. Award if 76 use
2. moles of glycolic acid used in titration= answer from 1, scaled by ratio in equation in 2bi
0.00400
CHECK equation in 2(b)(i)
3A. moles of glycolic acid in 250 cm3= (answer from 2)x 10= 0.0400 mol
OR3B. mass of glycolic in 25 cm3
= (answer from 2)x Mrof glycolic acid 0.304 gOR3C. concentration of glycolic acid
= (answer from 2) x 1000/25 0.16 mol dm-3
4. Mrof glycolic acid = 76.(0)
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F334 Mark Scheme
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Question Answer Marks
5A. moles of glycolic acid in 100 cm3
= (answer from 3A) x 100/14 0.286 molOR5Bi. mass of glycolic acid in 250 cm3
= (answer from 3A) x Mrof glycolic acid 3.04 g
OR5Bii.mass of glycolic in 250 cm3
= (answer from 3B) x 10 = 3.04 gOR5C. concentration of undiluted glycolic acid
= (answer from 3C) x 250/142.86 mol dm-3
ALLOWecf for instepALLOW AcnegonALLOWanswers
The following on tcorresponding coof working or lack21.7 scores 61.22 scores 5 (er12.2 scores 5 (er2.17 scores 5 (er3.04 scores 5 (erthese to other sf Omark less
If one of the answnumber of ticks
6. mass of glycolic acid in 100 cm3undiluted= (answer from 5A) x Mrof glycolic acid
OR = (answer from5B)x 100/14
OR = (answer from 5C/10) x Mrof glycolic acid
= 21.7 (3 sf)ANDcorrect comment
(c) (i)
H3C
O
O CH2CH2CH2CH3
butyl ethanoate
ester link correct
2 IGNORE where this includedALLOWadjacent
ALLOWbutyletha
(ii) butan-1-ol
concentrated sulfuric acid/hydrochloric acid
2 MUST HAVEnumDO NOT ALLOWALLOWformula fIGNOREspelling clear
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F334 Mark Scheme
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Question Answer Marks
(iii) ethanoic acid:hydrogen bonding IGNOREpd-pd
compound D:pd-pd hydrogen bonding is CON
instantaneous dipole induced dipole / id-id in both
3 ALLOWpd-pALLOW Van
(d) (i) The answer requires a comment for a carboxylic acid AND analcohol so award ONE mark from each section below:
CARBOXYLIC ACID(strong) peak at 1743 (cm1) shows C=O in ester not acidORno peak 1700 1725 (cm1) shows no C=O in acidORno broad peak at 2500 3200 (cm1) shows no OH in acid
ALCOHOLno peak greater than 3000 / in range 3200 3600 (allow 3640) sono OH in alcohol
2 answers may
to score eachwhich it is fou
ALLOW carboethanoic acid
FOR OHALFOR C=OAL
(ii) peak at m/z73:CH3COOCH2/ C3H5O2positive charge on any formula
species lost:CH2CH2CH3/ C3H7 (NO charge)
3 ALLOW any cfor both answALLOWC4H9
IFC4H9O+giv
THEN specie
(e) (i) nucleophilicaddition 2
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F334 Mark Scheme
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Question Answer Marks
(ii)
H C H
O
-C N
H C H
OH
CN
H C H
O-
CN
H+or H2O or HCN
HCHO with bond polarity correct CNwith lone pair of electrons on C
both curly arrows correct (lower one must be from C of CN) intermediate ion correct gain of H+from water, HCNor directto form the cyanohydrin
5
ALLOW CNALLOWve c
IGNOREany intermediate
Total 28
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F334 Mark Scheme
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Question Answer Marks
3 (a) (i)repeating unit in DNA is a nucleotide
formed from pentose/sugar/deoxyribose, phosphateand a baseAW
2 mark separate
ALLOW
names fof base
a namedIGNOREribosfor two marksmakes up the
(ii) proteins are formed from amino acid(s) 1
(iii) proteins have moreamino acids than the bases/nucleotides inDNA
from which to construct many unique/different/morestructures/arrangements/combinations to carry genetic data AW
2 ALLOWactuaacids in proteDNA
(b)
N N
CH3
O
O
HDNA chain
DNA chaincorrect formula completed for adenineANDboth H bonds betweencorrect atoms correct polarities for one hydrogen bond lone pair for one hydrogen bond
3
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F334 Mark Scheme
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Question Answer Marks
(c) (i)
HN CH C
CH2
HN
O
OH
CCH2C
O
CHN
O
CH
OH
H3C
CH3
ANY TWO of the THREE CORRECT chiral Cs ONLY
1
(ii) arrows as in (d) (i) 1 IGNOREextraends of chainAny other arro
(iii)
H2N C C
H2C
H O
O-
OH
correct amino acid (see opposite)
correct formula of ion
2 IGNOREany ALLOWany cIGNORE spec
and left
IGNORE
added
negati
COO
NO ecfIFanion formeamino acid
(iv) secondary:
folding/twisting of polypeptide/amino acid chains/primary structure
tertiary:further/final folding OR3D shape/structure
2
ALLOW(alphpleated sheet
ALLOWovera
Total 14
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F334 Mark Scheme
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Question Answer Marks
4 (a) (i)
O O SS
O
O
O
O
O
O
2-
x
xx
x x
xx
xx
xx
xx
xx
xx
x
xx
xx
xx
xx
correct inside oval (around peroxy Os) rest correct
2
ALLOWanot
second mark
(ii) (NH4)2S2O8 1 ALLOW
with co
S2O8(N
(b) S2O82(is the stronger oxidising agent) because
S2O82 hasa more positiveEovalue indicates a greatertendency AW to gain/attract/accept electrons/to
be reduced
ORA ie:S2O8
2 (is the stronger oxidising agent) because Cr2O72 hasa less
positive/ more negativeEovalue
indicates a smaller tendency AW to gain/attract/accept electrons/tobe reducedORindicates a greatertendency AW to lose electrons/to beoxidised
2 without refere
only scores 1
NOT higher fboth statemen
(c) (i) S2O82+ 2I 2SO4
2+ I2correct equation balanced
1 IGNOREstate
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5/28/2018 142261 Mark Scheme Unit f334 Chemistry of Materials January
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F334 Mark Scheme
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Question Answer Marks
(ii)
1. use filter of complementarycolour to iodine/solution
2. zero colorimeter with water
3. measure absorbance readings of standard solutions/solutionsof known concentration (of iodine)
4. plot calibration graph
5. take absorbance readings of the reacting mixture atknown/certain times AW (must refer to time may state unitsof time)
6. convert absorbance readings to iodine concentrations usingthe calibration curve
QWC:In order to gain the mark for point 3, 5 or 6, absorbance must beusedANDspelled correctly at least once
6 Using starchCANNOT gaiALLOW
filter/wabsorp
green/
suitab
orange/yellowNOT solvent
IGNORErefe
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F334 Mark Scheme
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Question Answer Marks
(iii)
t1/2t1/2
suitable graph sketched
construction lines to determine half-lives from graph
constant half-life (means first order)
3 graph should decreasingfrcurve will do)
at least twosshown on gra
dependent on(numbers on s
(d) (i) homogeneous, reactants and catalyst/Fe3+are in the same phase /state
1 MUSTmentioIGNORE'redoNOT'substratALLOW all in
(ii) Fe2+ 1s22s22p6 3s23p63d6Fe3+ 1s22s22p63s23p63d5
correct number of EXTRAelectrons added14(Fe2+) and 13(Fe3+) both fully correct
2 IGNORE 4s0
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F334 Mark Scheme
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Question Answer Marks
(iii) 1. Fe3+reacts with/oxidises IORA
2Fe3+ + 2I 2Fe2+ + I2
explanation:
the EoofFe3+/Fe2+half-cell is more posit ive / less negativethan that of the I/ I2
half-cell ORAAW
2. Fe2+reacts with/reduces S2O82ORA
S2O82
+ 2Fe2+ 2SO4
2 + 2Fe
3+
explanation:the EoofS2O8
2/SO42half-cell is more positivethan that of
the Fe3+/Fe2+half-cell ORAAW
QWC: to gain the explanation mark for either 1or 2, the datahas to be linked correctly to the reaction
6 IGNORE refevariable valen
ALLOWEoof
ALLOWEoof
NOTEIf answer starmark but ecf sget 5 marks
(e) (i) Rate = k x [S2O82
] x [I
] 2 IGNOREstate
(ii) uses one of the 3 sets of results:1. k = 2.0 x 105/ (0.075 x 0.040)2. k = 4.0 x 105/ (0.150 x 0.040)3. k = 1.0 x 105/ (0.075 x 0.020)
k = 0.0067
mol1dm3s1
3 ecf from part eALLOWstandCorrect numefor calculation
NO ecf from f
ALLOWany nNOT 0.006 N
ALLOWunits
(iii) 2.0 x 105mol dm3s1
2 Mark separate
Total 31
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