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General Certificate of Education
Chemistry 5421
CHM4
Further Physical and Inorganic
Chemistry
Mark Scheme
June examination - 2009 series
Mark schemes are prepared by the Principal Examiner and considered, together with the
relevant questions, by a panel of subject teachers. This mark scheme includes any
amendments made at the standardisation meeting attended by all examiners and is the scheme
which was used by them in this examination. The standardisation meeting ensures that the
mark scheme covers the candidates responses to questions and that every examiner
understands and applies it in the same correct way. As preparation for the standardisation
meeting each examiner analyses a number of candidates scripts: alternative answers not
already covered by the mark scheme are discussed at the meeting and legislated for. If, after
this meeting, examiners encounter unusual answers which have not been discussed at the
meeting they are required to refer these to the Principal Examiner.
It must be stressed that a mark scheme is a working document, in many cases further
developed and expanded on the basis of candidates reactions to a particular paper.
Assumptions about future mark schemes on the basis of one years document should be
avoided; whilst the guiding principles of assessment remain constant, details will change,
depending on the content of a particular examination paper.
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Chemistry - AQA GCE Mark Scheme 2009 June series
SECTION A
Q
Part
(a)
Sub
Part
Marking Guidance
(i)
Expt 2
Mark
1.8 10-3
or
8.1 10-5
Expt 3
6.75
k
Comments
If k used for the calculation:
if rounded to 3.8 103 allow answer 1.78 103
or k(2.16 10-8)
If k used for the calculation:
if rounded to 3.8 103 allow answer 8.2 10-5
and if calc rounded to (3.8 103) (2.2 10-8) = 8.4
10-5
6.7 10-4
Expt 4
or (1.67 10-3 /k)
If k used for the calculation:
if rounded to 3.8 103 allow answer 6.6 10-4
Allow 0.7 10-3 or 7 10-4
1
(a)
(b)
(ii)
k =
rate
[P][Q]2
1.8 10 -5
(1.2 10 3 ) (2.0 10 - 3 ) 2
Mark is for insertion of numbers
If upside down, score only units mark consequential on
their expression for k
3750 or 3.75 103 or 3.8 103
If k is wrong, check whether apparently wrong answers
in part(i) are correct conseq to wrong k.
mol-2dm6s-1
Any order
Horizontal straight line
Be generous, they need not use a ruler.
Chemistry - AQA GCE Mark Scheme 2009 June series
Q
2
Part
Sub
Part
Marking Guidance
The Statement : mol fraction =
(a)
Mark
mol NO2
total moles
either in this form or using their numbers, gets max 1 if
answer to par (a) is wrong because of wrong no of
moles (CE) of either NO2 or N2O4 or total
mol N2O4 = 1.20 - (0.36) = 1.0(2)
M1
total moles = 1.0(2) + 0.36 = 1.36 or 1.38 or 1.4
0.36
mol fraction of NO2 =
= 0.26
1.38
Comments
6
allow
23
M2
If AE earlier, this mark is for (previous answer + 0.36)
M3
If AE earlier, this mark is for
allow (0.36/1.36) = 0.264 to (0.36/1.4) = 0.257
0.36
previous answer
(b)
(i)
pp = mol fract Total Pressure
Or allow symbols
(b)
(ii)
ppNO2 = 0.28 180 = 50(.4)
Mark for answer
ppN2O4 = 180 50.4 = 129.6 or 130
Mark for answer = (180 previous answer)
if Kp wrong, allow units mark only conseq to their Kp
(c)
(c)
(i)
(ii)
Kp
(pNO2 ) 2
pN2O 4
penalise [ ] but mark on;
49.6 2
132.0
18.6 or 19
kPa
conseq on their Kp
allow mol dm-3 if K given with [ ]
Chemistry - AQA GCE Mark Scheme 2009 June series
Penalise pH to <2dp> once in the paper
Part
3
3
Sub
Part
Marking Guidance
Mark
Comments
(a)
(i)
pH = log[H+]
Penalise ( ) once in question
(a)
(ii)
mol HCl = (5.0 10-3) 0.135 = 6.75 10-4 (or 6.8 10-4)
Mark is for answer if wrong, no further mark in part
(a)(ii)
pH = 3.17
Lose this mark if moles divided by 0.995
M1
Penalise ( ) once in question
(b)
(b)
(i)
(ii)
Ka =
[H + ] [CH 3 CHClCOO - ]
[CH 3 CHClCOOH]
[H + ] 2
[CH 3 CHClCOOH]
[H+] = (1.48 10-3 0.350)
pH = 1.64
allow molecular formulae
Penalise [H+]2/[CH3CHClCOOH] but this can score M2
or minor slip in formulae
Not allow [H+][A-]/[HA]
M2
Allow [H+]2/[HA] or minor slip in formula
= 2.28 102
M3
Mark for 2.28 102 ( allow 2.3 102 - this still gives
1.64)
(can give three ticks here for (b)(ii))
M4
use of quadratic gives 1.66
3.29 gets 2 marks if visible in calculation, but square
root not taken (AE), else gets 1
(c)
Decrease but mark on if incorrect
increase T increases dissociation /favours forward reaction /
moves to right / favours endothermic reaction
increases [H+] or more H+
Chemistry - AQA GCE Mark Scheme 2009 June series
(d)
Optical
(plane) polarised light or polarimeter
(light) rotated in opposite (or wtte) directions QOL
3
(e)
[H+] = 10-4.69 = 2.0(4) 10-5
Ka =
(2.04 10 -5 ) (0.10)
(0.15)
0.10
or
pKa = 4.69 log (
or
pKa = 4.86 or 4.87
= 1.36 10-5 (allow 1.3 10-5 to 1.4 10-5 )
0.15
If wrong type, no further marks but mark on from just
stereoisomerism
Not just in different directions
M1
If [H+] wrong, due to CE, allow numbers in expression
for one mark out of three for M2
M2
If 0.10/0.15 upside down or if moles added to or
subtracted from salt or acid, can only score M1
M3
ignore units
Chemistry - AQA GCE Mark Scheme 2009 June series
Part
Sub
Part
Marking Guidance
Mark
(a)
(i)
proton acceptor
(a)
(ii)
butylamine
alkyl group is electron releasing/ increases e density on
N/has (+) inductive effect
CH3
lone pair more available
CH3CH2 N
CH3
(b)
(c)
(i)
(c)
(ii)
(d)
(i)
Comments
Or formula - if wrong, no further marks in (a)(ii)
1
1
Allow C2H5
Mark part (ii) independent of part (i)
quaternary ammonium (salt) or tetraalkylammonium (salt)
(QOL)
Or quaternary alkylammonium (salt)
(cationic) surfactant/ fabric softener/water repellents /
fungicides / emulsifiers/ paper softeners/antistatic
agents/corrosion inhibitors/ disinfectants/antistatic agents
(e.g. in shampoo)/hair conditioners /spermicidal
jellies/detergents
N-methylethanamide
CH3(CH2)17N(CH3)3
(Br )
Allow N-methylacetamide
M2
H3C
(d)
(ii)
Cl
M1 M3 for structure
(Nucleophilic) addition-elimination
CH3
Chemistry - AQA GCE Mark Scheme 2009 June series
O
H3C
H3C
Cl
H
NH2for 3 arrows
M4
and lone pair
Penalise electrophilic ..
M2 not allowed independent of M1, but
allow M1 for correct attack on C+
+C=O loses M2
only allow M4 after correct or very close M3
lose M4 for Cl removing H+ in mechanism, but
ignore HCl as a product
(e)
(i)
CH3
H3N
COO
(e)
CH3
(ii)
H3N
allow -CO2H
dont penalise position of + on NH3
Allow -CO2CH3
COOH
(e)
(iii)
CH3
H2N
C
H
COOCH3
or H3N
Chemistry - AQA GCE Mark Scheme 2009 June series
Q
5
Part
(a)
Sub
Part
Marking Guidance
(i)
HCl
AlCl3
H2C
(a)
(ii)
Mark
or HBr
ignore g aq conc etc
or AlBr3 FeCl3 FeBr3
CH2
M1
+ HCl
structure
electrophilic substitutionH
CH2CH3
ignore g aq conc etc
+ AlCl3 M2
CH3CH2
1 The two substances can be
+ AlC
CH2CH3
M3 arrow
Allow
Kekule
structures
Be lenient
on position
of + in
electrophile
unless
definitely on
CH3
(b)
Comments
chloroethane usually made from ethene or more difficult to
CH
CH2
make
1 in either order
1 Ignore position of + or on ions
Allow C2H4
1 Not Friedel Crafts
3 M1 arrow from within hexagon to C of CH2 or to + on
C of CH2
horseshoe must not extend beyond C2 to C6 but can
be smaller
+ not too close to C1
M3 arrow into hexagon unless Kekule
allow M3 arrow independent of M2 structure
ignore base removing H in M3
1 Not just cheaper - indication of cost must be qualified
Not just ethene is more readily available
ethene is a (by)product of cracking
5
(c)
1 Ignore n or brackets, but must have trailing bonds
Addition or radical or step (QOL)
1 Not additional
Chemistry - AQA GCE Mark Scheme 2009 June series
Part
(a)
Sub
Part
Marking Guidance
C (CH2)4 acid
C N
hexan(e)dioic
O
(CH2)6
(1)
CH2
H2C
H2C
peptide link
must be
shown to
score
at all
CO
(1)
or
O
CH2
or
C
O
allow
or
O
CONHCO
Mark
Comments
Ignore 1,6 but penalise other numbers
NOT C4H8 or C6H12
Not
H2
CH3 CH3
HOOC
(b)
COOH
1
O
HOOC
CH2
C
O
(c)
CH2CH2CH3
1
1
or C3H7 or
CH(CH3)2
6
(d)
Allow CO2H
2 peaks
a 2.1 2.6 or value within the range
b 3.7 4.1 or value within the range
10
Chemistry - AQA GCE Mark Scheme 2009 June series
(e)
(f)
c doublet or duplet
d doublet or duplet
O O
CH3CH2O+ or C2H5O+
[ H3CH2C O C C
OCOCOOCH2CH3
CH2CH3 ]+ . CH CH + +
3
2
+ on O or outside brackets
Allow molecular formulae
[C6H10O4]+
(1) for Molecular ion
(1) for RHS of
equation
Allow + on CH3CH
. 2 or
allow (COO)2C2H5 etc
dot on radical anywhere
11
C2H5+ + [C4H5O4]
Chemistry - AQA GCE Mark Scheme 2009 June series
Q
7
Part
Sub
Part
Marking Guidance
Mark
Comments
X propene or CH3CH=CH2
contradiction loses the mark
Ignore C3H6
Y propan-1-ol or 1- propanol or CH3CH2CH2OH
contradiction loses the mark
Not propan-2-ol nor C3H7OH
Ignore propanol if correct structure also give
If reagent wrong or missing, no mark for
conditions, but allow conditions following minor
slip in formula
Ignore temperature throughout
Reaction 1
KOH or NaOH
Any mention of conc sulphuric loses both reagent
and condition marks
Incomplete reagent e.g. OH- penalise once but
can score conditions marks in both Reaction 1
and 3
(Hot) alcoholic or ethanolic
Not ethanoic
Reaction 2
HBr or KBr/H2SO4(with or without conc or dil)
Not KBr alone ignore extra (conc) H2SO4
Reaction 3
KOH or NaOH
Any mention of conc sulphuric loses both reagent
and condition marks
(Warm) aqueous
K2Cr2O7/acidified or H+ or KMnO4/acidified or
H+
reflux
Reaction 4
12
Not Fehlings/Tollens
reagent again
penalise incomplete
Chemistry - AQA GCE Mark Scheme 2009 June series
Part
(a)
Sub
Part
Marking Guidance
mol HCl
[CO32-]
20.8
10 3
0.150 =
3.12 10-3
allow 3.1
10-3
= (3.12 10-3) 103/25
(b)
0.124 or
0.12
2nd volume/amount HCl is used to react with
(original
HCO3-)
(HCO3-
Comments
M1
Mark for answer
25
0.150 as AE and allow conseq M2
Treat
3
10
and M3
M2
= 0.125 (mol dm-3) or 0.13
8
Mark
Mark for previous answer 1000/25
M3
M4
formed in Reaction 1)
If no subtraction, allow max 1 for mol HCl or H+
added in second step
vol HCl for original HCO3- = 33.25 20.80 = 12.45 cm3
M5
or second mol HCl added =
5(.0) 10-3
mol HCl = (12.45 10-3) 0.150
= 1.87 10-3
= mol HCO3- in 25 cm3
[HCO3-] = (1.87 10-3) 1000/25
M6
0.0748 or 0.075
13
M7
33.25
0.150
10 3
-3
= 4.99 10
or
or Mol HCl used with HCO3- = 4.99 10-3 3.12 10-3
= 1.87
10-3
4
