PMT

A-LEVEL
Chemistry
7405/2 Organic and Physical Chemistry
Mark scheme

7405
June 2017

Version: 1.0 Final

 PMT

Mark schemes are prepared by the Lead Assessment Writer and considered, together with the
relevant questions, by a panel of subject teachers. This mark scheme includes any amendments
made at the standardisation events which all associates participate in and is the scheme which was
used by them in this examination. The standardisation process ensures that the mark scheme covers
the students’ responses to questions and that every associate understands and applies it in the same
correct way. As preparation for standardisation each associate analyses a number of students’
scripts. Alternative answers not already covered by the mark scheme are discussed and legislated
for. If, after the standardisation process, associates encounter unusual answers which have not been
raised they are required to refer these to the Lead Assessment Writer.

It must be stressed that a mark scheme is a working document, in many cases further developed and
expanded on the basis of students’ reactions to a particular paper. Assumptions about future mark
schemes on the basis of one year’s document should be avoided; whilst the guiding principles of
assessment remain constant, details will change, depending on the content of a particular
examination paper.

Further copies of this mark scheme are available from aqa.org.uk

Copyright © 2017 AQA and its licensors. All rights reserved.

AQA retains the copyright on all its publications. However, registered schools/colleges for AQA are permitted to copy material from this
booklet for their own internal use, with the following important exception: AQA cannot give permission to schools/colleges to photocopy any
material that is acknowledged to a third party even for internal use within the centre.
 PMT

MARK SCHEME – A-LEVEL CHEMISTRY – 7405/2 – JUNE 2017

A-Level Chemistry
Mark Scheme Instructions for Examiners
1. General
The mark scheme for each question shows:
 the marks available for each part of the question
 the total marks available for the question
 the typical answer or answers which are expected
 extra information to help the examiner make his or her judgement and help to delineate what is acceptable or not worthy of credit or, in
discursive answers, to give an overview of the area in which a mark or marks may be awarded.
The extra information in the ‘Comments’ column is aligned to the appropriate answer in the left-hand part of the mark scheme and should only
be applied to that item in the mark scheme.
You should mark according to the contents of the mark scheme. If you are in any doubt about applying the mark scheme to a particular
response, consult your Team Leader.
At the beginning of a part of a question a reminder may be given, for example: where consequential marking needs to be considered in a
calculation; or the answer may be on the diagram or at a different place on the script.
In general the right-hand side of the mark scheme is there to provide those extra details which might confuse the main part of the mark
scheme yet may be helpful in ensuring that marking is straightforward and consistent.
The use of M1, M2, M3 etc in the right-hand column refers to the marking points in the order in which they appear in the mark scheme. So, M1
refers to the first marking point, M2 the second marking point etc.

2. Emboldening
2.1 In a list of acceptable answers where more than one mark is available ‘any two from’ is used, with the number of marks emboldened.
Each of the following bullet points is a potential mark.
2.2 A bold and is used to indicate that both parts of the answer are required to award the mark.

3 of 32
 PMT

MARK SCHEME – A-LEVEL CHEMISTRY – 7405/2 – JUNE 2017

2.3 Alternative answers acceptable for a mark are indicated by the use of OR. Different terms in the mark scheme are shown by a / ; eg
allow smooth / free movement.

3. Marking points
3.1 Marking of lists
This applies to questions requiring a set number of responses, but for which students have provided extra responses. The general
‘List’ principle to be followed in such a situation is that ‘right + wrong = wrong’.
Each error / contradiction negates each correct response. So, if the number of error / contradictions equals or exceeds the number of
marks available for the question, no marks can be awarded.
However, responses considered to be neutral (often prefaced by ‘Ignore’ in the mark scheme) are not penalised.
For example, in a question requiring 2 answers for 2 marks:

Incorrect
Correct answers (i.e.
Mark (2) Comment
answers incorrect rather
than neutral)
1 0 1
They have not exceeded the maximum
1 1 1
number of responses so there is no penalty.
They have exceeded the maximum number
1 2 0 of responses so the extra incorrect
response cancels the correct one.
2 0 2
2 1 1
2 2 0
3 0 2 The maximum mark is 2
3 1 1 The incorrect response cancels out one of

4 of 32
 PMT

MARK SCHEME – A-LEVEL CHEMISTRY – 7405/2 – JUNE 2017

the two correct responses that gained

credit.
Two incorrect responses cancel out the two
3 2 0
marks gained.
3 3 0

3.2 Marking procedure for calculations

Full marks should be awarded for a correct numerical answer, without any working shown, unless the question states ‘Show your
working’ or ‘justify your answer’. In this case, the mark scheme will clearly indicate what is required to gain full credit.
If an answer to a calculation is incorrect and working is shown, process mark(s) can usually be gained by correct substitution / working
and this is shown in the ‘Comments’ column or by each stage of a longer calculation.

3.3 Errors carried forward, consequential marking and arithmetic errors

Allowances for errors carried forward are most likely to be restricted to calculation questions and should be shown by the abbreviation
ECF or consequential in the marking scheme.
An arithmetic error should be penalised for one mark only unless otherwise amplified in the marking scheme. Arithmetic errors may
arise from a slip in a calculation or from an incorrect transfer of a numerical value from data given in a question.

3.4 Equations
In questions requiring students to write equations, state symbols are generally ignored unless otherwise stated in the ‘Comments’
column.
Examiners should also credit correct equations using multiples and fractions unless otherwise stated in the ‘Comments’ column.

3.5 Oxidation states

In general, the sign for an oxidation state will be assumed to be positive unless specifically shown to be negative.

5 of 32
 PMT

MARK SCHEME – A-LEVEL CHEMISTRY – 7405/2 – JUNE 2017

3.6 Interpretation of ‘it’

Answers using the word ‘it’ should be given credit only if it is clear that the ‘it’ refers to the correct subject.

3.7 Phonetic spelling

The phonetic spelling of correct scientific terminology should be credited unless there is a possible confusion with another technical
term or if the question requires correct IUPAC nomenclature.

3.8 Brackets
(…..) are used to indicate information which is not essential for the mark to be awarded but is included to help the examiner identify the
sense of the answer required.

3.9 Ignore / Insufficient / Do not allow

Ignore or insufficient is used when the information given is irrelevant to the question or not enough to gain the marking point. Any
further correct amplification could gain the marking point.
Do not allow means that this is a wrong answer which, even if the correct answer is given, will still mean that the mark is not awarded.

3.10 Marking crossed out work

Crossed out work that has not been replaced should be marked as if it were not crossed out, if possible. Where crossed out work has
been replaced, the replacement work and not the crossed out work should be marked.

6 of 32
 PMT

MARK SCHEME – A-LEVEL CHEMISTRY – 7405/2 – JUNE 2017

3.11 Reagents
The command word “Identify”, allows the student to choose to use either the name or the formula of a reagent in their answer. In
some circumstances, the list principle may apply when both the name and the formula are used. Specific details will be given in mark
schemes.

The guiding principle is that a reagent is a chemical which can be taken out of a bottle or container. Failure to identify complete
reagents will be penalised, but follow-on marks (e.g. for a subsequent equation or observation) can be scored from an incorrect
attempt (possibly an incomplete reagent) at the correct reagent. Specific details will be given in mark schemes.

For example, no credit would be given for

 the cyanide ion or CN– when the reagent should be potassium cyanide or KCN;
 the hydroxide ion or OH– when the reagent should be sodium hydroxide or NaOH;
 the Ag(NH3)2+ ion when the reagent should be Tollens’ reagent (or ammoniacal silver nitrate). In this example, no credit is given for
the ion, but credit could be given for a correct observation following on from the use of the ion. Specific details will be given in mark
schemes.

In the event that a student provides, for example, both KCN and cyanide ion, it would be usual to ignore the reference to the cyanide
ion (because this is not contradictory) and credit the KCN. Specific details will be given in mark schemes.

3.12 Organic structures

Where students are asked to draw organic structures, unless a specific type is required in the question and stated in the mark scheme,
these may be given as displayed, structural or skeletal formulas or a combination of all three as long as the result is unambiguous.
In general
 Displayed formulae must show all of the bonds and all of the atoms in the molecule, but need not show correct bond angles.
 Skeletal formulae must show carbon atoms by an angle or suitable intersection in the skeleton chain. Functional groups must be
shown and it is essential that all atoms other than C atoms are shown in these (except H atoms in the functional groups of
aldehydes, secondary amines and N-substituted amides which do not need to be shown).

7 of 32
 PMT

MARK SCHEME – A-LEVEL CHEMISTRY – 7405/2 – JUNE 2017

 Structures must not be ambiguous, e.g. 1-bromopropane should be shown as CH3CH2CH2Br and not as the molecular formula
C3H7Br which could also represent the isomeric 2-bromopropane.
 Bonds should be drawn correctly between the relevant atoms. This principle applies in all cases where the attached functional
group contains a carbon atom, e.g nitrile, carboxylic acid, aldehyde and acid chloride. The carbon-carbon bond should be clearly
shown. Wrongly bonded atoms will be penalised on every occasion. (see the examples below)
 The same principle should also be applied to the structure of alcohols. For example, if students show the alcohol functional group
as C ─ HO, they should be penalised on every occasion.
 Latitude should be given to the representation of C ─ C bonds in alkyl groups, given that CH3─ is considered to be interchangeable
with H3C─ even though the latter would be preferred.
 Similar latitude should be given to the representation of amines where NH2─ C will be allowed, although H2N─ C would be preferred.
 Poor presentation of vertical C ─ CH3 bonds or vertical C ─ NH2 bonds should not be penalised. For other functional groups, such
as ─ OH and ─ CN, the limit of tolerance is the half-way position between the vertical bond and the relevant atoms in the attached
group.
By way of illustration, the following would apply.

CH3 C C C OH C C

CH3 CH3CH2 OH

allowed allowed not allowed not allowed not allowed

NH2 NO2

NH2 C C

NH2
NH2

allowed allowed allowed allowed not allowed

8 of 32
 PMT

MARK SCHEME – A-LEVEL CHEMISTRY – 7405/2 – JUNE 2017

CN C C COOH C C C

CN COOH COOH

not allowed not allowed not allowed not allowed not allowed

CHO C C C COCl C C

CHO CHO COCl

not allowed not allowed not allowed not allowed not allowed

 Representation of CH2 by CH2 will be penalised

 Some examples are given here of structures for specific compounds that should not gain credit (but, exceptions may be made in
the context of balancing equations)

CH3COH for ethanal

CH3CH2HO for ethanol

OHCH2CH3 for ethanol
C2H6O for ethanol

CH2CH2 for ethene

CH2.CH2 for ethene
CH2:CH2 for ethane

9 of 32
 PMT

MARK SCHEME – A-LEVEL CHEMISTRY – 7405/2 – JUNE 2017

 Each of the following should gain credit as alternatives to correct representations of the structures.

CH2 = CH2 for ethene, H2C=CH2

CH3CHOHCH3 for propan-2-ol, CH3CH(OH)CH3

 In most cases, the use of “sticks” to represent C ─ H bonds in a structure should not be penalised. The exceptions to this when
“sticks” will be penalised include
 structures in mechanisms where the C ─ H bond is essential (e.g. elimination reactions in halogenoalkanes and alcohols)
 when a displayed formula is required
 when a skeletal structure is required or has been drawn by the candidate

3.13 Organic names

As a general principle, non-IUPAC names or incorrect spelling or incomplete names should not gain credit. Some illustrations are
given here.

but-2-ol should be butan-2-ol

2-hydroxybutane should be butan-2-ol
butane-2-ol should be butan-2-ol
2-butanol should be butan-2-ol
ethan-1,2-diol should be ethane-1,2-diol
2-methpropan-2-ol should be 2-methylpropan-2-ol
2-methylbutan-3-ol should be 3-methylbutan-2-ol
3-methylpentan should be 3-methylpentane
3-mythylpentane should be 3-methylpentane
3-methypentane should be 3-methylpentane
propanitrile should be propanenitrile
aminethane should be ethylamine (although aminoethane can gain credit)

10 of 32
 PMT

MARK SCHEME – A-LEVEL CHEMISTRY – 7405/2 – JUNE 2017

2-methyl-3-bromobutane should be 2-bromo-3-methylbutane

3-bromo-2-methylbutane should be 2-bromo-3-methylbutane
3-methyl-2-bromobutane should be 2-bromo-3-methylbutane
2-methylbut-3-ene should be 3-methylbut-1-ene
difluorodichloromethane should be dichlorodifluoromethane

3.14 Organic reaction mechanisms

Curly arrows should originate either from a lone pair of electrons or from a bond.
The following representations should not gain credit and will be penalised each time within a clip.

. . Br
H3C Br H3C .. Br H3C

_ .._
: OH OH
For example, the following would score zero marks

H3C C Br

HO H

When the curly arrow is showing the formation of a bond to an atom, the arrow can go directly to the relevant atom, alongside the
relevant atom or more than half-way towards the relevant atom.

11 of 32
 PMT

MARK SCHEME – A-LEVEL CHEMISTRY – 7405/2 – JUNE 2017

In free-radical substitution
 the absence of a radical dot should be penalised once only within a clip.
 the use of half-headed arrows is not required, but the use of double-headed arrows or the incorrect use of half-headed arrows in
free-radical mechanisms should be penalised once only within a clip

The correct use of skeletal formulae in mechanisms is acceptable, but where a C-H bond breaks both the bond and the H must be
drawn to gain credit.

3.15 Extended responses

For questions marked using a ‘Levels of Response’ mark scheme:
Level of response mark schemes are broken down into three levels, each of which has a descriptor. Each descriptor contains two statements.
The first statement is the Chemistry content statement and the second statement is the communication statement.

Determining a level

Start at the lowest level of the mark scheme and use it as a ladder to see whether the answer meets the Chemistry content descriptor for that
level. The descriptor for the level indicates the qualities that might be seen in the student’s answer for that level. If it meets the lowest level,
then go to the next one and decide if it meets this level, and so on, until you have a match between the level descriptor and the answer.
When assigning a level you should look at the overall quality of the answer and not look to pick holes in small and specific parts of the answer
where the student has not performed quite as well as the rest. If the answer covers different aspects of different levels of the mark scheme you
should use a best fit approach for defining the level.

Once the level has been decided, the mark within the level is determined by the communication statement:
• If the answer completely matches the communication descriptor, award the higher mark within the level.
• If the answer does not completely match the communication descriptor, award the lower mark within the level.

12 of 32
 PMT

MARK SCHEME – A-LEVEL CHEMISTRY – 7405/2 – JUNE 2017

The exemplar materials used during standardisation will help you to determine the appropriate level. There will be an exemplar in the
standardising materials which will correspond with each level of the mark scheme and for each mark within each level. This answer will have
been awarded a mark by the Lead Examiner. You can compare the student’s answer with the exemplar to determine if it is the same standard,
better or worse than the example. You can then use this to allocate a mark for the answer based on the Lead Examiner’s mark on the
exemplar.
You may well need to read back through the answer as you apply the mark scheme to clarify points and assure yourself that the level and the
mark are appropriate.
Indicative content in the mark scheme is provided as a guide for examiners. It is not intended to be exhaustive and you must credit other
chemically valid points. Students may not have to cover all of the points mentioned in the indicative content to reach the highest level of the
mark scheme. The mark scheme will state how much chemical content is required for the highest level.
An answer which contains nothing of relevance to the question must be awarded no marks.

For other extended response answers:

Where a mark scheme includes linkage words (such as ‘therefore’, ‘so’, ‘because’ etc), these are optional. However, a student’s marks for the
question may be limited if they do not demonstrate the ability to construct and develop a sustained line of reasoning which is coherent,
relevant, substantiated and logically structured. In particular answers in the form of bullet pointed lists may not be awarded full marks if there is
no indication of logical flow between each point or if points are in an illogical order.
The mark schemes for some questions state that the maximum mark available for an extended response answer is limited if the answer is not
coherent, relevant, substantiated and logically structured. During the standardisation process, the Lead Examiner will provide marked
exemplar material to demonstrate answers which have not met these criteria. You should use these exemplars as a comparison when marking
student answers.

13 of 32
 PMT

MARK SCHEME – A-LEVEL CHEMISTRY – 7405/2 – JUNE 2017

Question Answers Mark Additional Comments/Guidance

01.1 1 Must be displayed

Nucleophilic substitution 1
01.2
Excess NH3 1 Ignore aqueous, alcoholic, conc, dil, temp, heat, pressure

If either Mr incorrect or used incorrectly then only award 1

Amount of CH3CH2CH2Br 25.2/122.9 (=0.205) (mol) M1 mark for 75% yield calculation
(ignore rounding to 123 for CH3CH2CH2Br)

01.3 Amount of CH3CH2CH2NH2 M1 x 0.75 (= 0.154) (mol) M2 OR Max mass amine = M1 x 59.0 (= 12.1) (g)

Actual mass = M2 x 0.75 = 9.07g Must be 3sf

Mass CH3CH2CH2NH2 M2 x 59.0 = 9.07g Must be 3sf M3 Allow 9.09 but if 9.08 check for AE
18.9 scores 1 for 75%

Must be skeletal
1 Ignore lone pair
01.4

tertiary amine or 3o amine (only award if a tertiary amine shown) 1

14 of 32
 PMT

MARK SCHEME – A-LEVEL CHEMISTRY – 7405/2 – JUNE 2017

Question Answers Mark Additional Comments/Guidance

Not aqueous
01.5 NaOH/ ethanol or KOH / ethanol (both required) 1 Ignore heat, temp, conc., dil,
Accept alcoholic for ethanol

(Basic) Elimination 1
M3
H H

H 3C C C Br
Also credit E1 mechanism

M1 M3 arrow and carbocation H H

H H H H

M2 H 3C C C+
:

OH H 3C C C Br

H H H M2 H
M1
01.6 M1 arrow from lone pair on O of hydroxide to correct H (or to
space mid way between hydroxide O and H) 3

:
OH

--
M2 arrow from C-H bond to C-C bond following attack by OH M3 curly arrow for loss of Br- & structure of carbocation
on the correct H
M1 arrow from lone pair on O of hydroxide to H (or to space
M3 arrow from C-Br bond to Br mid way between hydroxide O and H) (same as E2)
If nucleophilic substitution shown then allow M3 only in M2 arrow from C-H bond to C-C bond (same as E2)
mechanism

If wrong haloalkane used then Max 2 for mechanism

Total 13

15 of 32
 PMT

MARK SCHEME – A-LEVEL CHEMISTRY – 7405/2 – JUNE 2017

Question Answers Mark Additional Comments/Guidance

Straight line through (0.00, 0.50) which If ‘tangent’ does not touch 0.5 mol dm-3 then CE=0 for 2.1 and
02.1 cuts time axis at between 5 and 12.5 secs OR 1 2.2.
conc 0.3 at time between 2s and 5s no tangent scores 0 in 2.1 and 2.2.

Mark is for correct calculation of their gradient : If ‘tangent’ does not touch 0.5 mol dm-3 then CE=0 for 2.1 and
e.g. 0.50/11 = 0.045 2.2
02.2 1
or 4.5 × 10-2 (mol dm-3 s-1) Ignore negative sign
(Expect a value between 0.04 and 0.1

new[A]2 = 1.7 × (0.50)2 Award 2 for 0.65

[A] increases by √1.7
= 0.425
Award 1 mark for an AE using a correct method
02.3 new[A] = 1.30 × 0.50
If candidate use their rate then CE=0
= 0.65 (mol dm-3) New [A] = 0.65 (mol dm-3) 2
2 sfs min 2 sfs min
0.85 scores 1 if √ shown

Total 4

16 of 32
 PMT

MARK SCHEME – A-LEVEL CHEMISTRY – 7405/2 – JUNE 2017

Question Answers Mark Additional Comments/Guidance

3.1 10 -3 Mark is for insertion of numbers into correctly rearranged rate

k = (rate/[C][D]) =) 1
(0.48)  (0.23) equation
03.1
= 2.8 × 10-2 min 2sfs 1

mol–1 dm3 s–1 1 Mark units separately in any order.

M1 = ln (their k)
-2
Alternative value
ln k = ln 2.8 × 10 (= - 3.58) M1 If incorrect then award
ln k = ln 3.2 × 10-3 = - 5.74
M2 and M3 only

if ln 16.9 used max 3

Ea = RT(ln A - ln k)
If temp used 25 max 2
OR M2
Incorrect
03.2  Ea = RT(ln k – ln A) rearrangement then
M1 only

Ea = 8.31 × 298 (16.9 + 5.74)

Ea = 8.31 × 298 (16.9 + 3.58) ( = 50716 J mol-1) M3
( = 56076 J mol-1)

-1 – 50.7 or -51 scores Ea = 56 kJ mol-1

Ea = 51 kJ mol M4
max 2

Total 7

17 of 32
 PMT

MARK SCHEME – A-LEVEL CHEMISTRY – 7405/2 – JUNE 2017

Question Answers Mark Additional Comments/Guidance

04.1 2-hydroxyhexanenitrile 1

(Plane) polarised light 1

04.2
Enantiomers would rotate light in opposite directions 1 not different alone

planar carbonyl group or

Not planar molecule,
planar 1
C O
not planar bond, not planar C=O
04.3 Attack from either side 1
With equal probability
OR produces equal amounts (of the two isomers/enantiomers) 1

OH Allow C2H5 or skeletal

1 OH
CH 3CH 2 C CH 2CH 3

CN
04.4
Does not contain a chiral centre 1
N
OR does not contain C attached to 4 different groups
M2 dependent on correct M1 (No structure = 0)
OR contains two identical/ethyl groups
If pentan-3-one drawn then allow symmetrical ketone for M2
OR symmetrical (product)

Total 8

18 of 32
 PMT

MARK SCHEME – A-LEVEL CHEMISTRY – 7405/2 – JUNE 2017

Question Answers Mark Additional Comments/Guidance

O Allow CH3COOCH2CH2OOCCH3
OR CH3COOCH2CH2OCOCH3
C CH2 O CH3 O
05.1 H 3C O CH2 C 1
O
O O

OR O

Mol HOCH2CH2OH = 6.00 × 10-2 OR 0.06(00) 1

-1
05.2 Mol C6H10O4 = 1.45 × 10 OR 0.145 1
-1
Mol H2O = 2.90 × 10 OR 0.29(0) 1

19 of 32
 PMT

MARK SCHEME – A-LEVEL CHEMISTRY – 7405/2 – JUNE 2017

[ester]  [H2 O] 2 Allow words for acid and alcohol

(Kc =) 1
[CH 3 COOH] 2  [HOCH 2 CH 2 OH]

The volume cancels out (Penalise a contradictory justification

05.3 from expression if the volumes do not cancel out)
OR
1
there are equal no of moles on each side of the equation
OR
there are equal no of molecules on each side of the equation

(8.02  10 1 / V )(1.15 / V ) 2 0.789 scores 3

2
(Mol CH3COOH/V) = 1 (8.02  10 1 )(1.15) 2
6.45  (2.64  10 / V ) Allow without V : (nCH3COOH)2 =
M1 6.45  (2.64  10 1 )
2
If (nCH3COOH) =0.623 then award M1 and M2

05.4 If Kc is correct in 05.3 but incorrect rearrangement, then

(8.02  10 1 )  (1.15) 2 CE=0 except if upside down rearrangement then M3 only
Mol CH3COOH = √ = 0.623 M2
awarded for 1.27
6.45  (2.64  10 1 )
If Kc is incorrect in 05.3 then only M1 can be awarded for
Mol CH3COOH = 0.789 (must be 3 sfs) Allow 0.788 – 0.790 M3 correct rearrangement.

Total 9

20 of 32
 PMT

MARK SCHEME – A-LEVEL CHEMISTRY – 7405/2 – JUNE 2017

Question Answers Mark Additional Comments/Guidance

Allow -CO2
H 3N CH C O

CH2 O Allow +H3N- and NH3+

06.1 1

H 2N CH COO
06.2 1
CH 2 OH

H 2N CH C N CH COOH If same wrong amino acid twice – max 1

CH2 O H CH2 OH

06.3 HOOC CH N C CH NH 2

CH 2 H O CH2OH

21 of 32
 PMT

MARK SCHEME – A-LEVEL CHEMISTRY – 7405/2 – JUNE 2017

Question Answers Mark Additional Comments/Guidance

(nucleophilic) addition-elimination M1 Not electrophilic addition-elimination.

M2 for arrow from lp on N to C
(or to space half way between N and C)
M3 Ignore + and  unless wrong
M4
O
O M3 for arrow from C=O bond to O
CH 3 CH 2 C CH 3 CH 2 C Cl M5 for 3 arrows and lp Not score M3 as an independent first step, but can allow M2
Cl for attack on C+ produced
CH 3 CH 2 N H
CH 3CH 2 NH 2
If Cl lost at this stage, Max 1 for mechanism for M2
H M2 –
06.4 M2 RNH 2 M5 M4 for structure of ion including 2 charges
(+ on N must be correct in both cases if drawn twice)
O
CH 3CH 2 C M5 for 3 arrows and lp on O
NH - may be scored in two steps
CH 2CH 3
Ignore use of RNH2 to remove H+ in M5, but penalise use of
Cl

N-ethylpropanamide M6

Total 10

Question Answers Mark Additional Comments/Guidance

22 of 32
 PMT

MARK SCHEME – A-LEVEL CHEMISTRY – 7405/2 – JUNE 2017

07.1 This question is marked using Levels of Response. Refer to the Indicative Chemistry content
Mark Scheme Instructions for Examiners for guidance.
Stage 1: An initial test to separate into two groups (2 groups
Level 3 All stages are covered and each stage is generally of 2 OR 1 group of 3 and 1 group of 1)
correct and virtually complete.
5-6 marks Stage 2: An second test to distinguish within a group or to
Answer is communicated coherently and shows a separate into two further groups
logical progression from Stage 1 to Stages 2 and 3 to
distinguish all the compounds with results for all Stage 3: A third test leads to a set of results/observations
remaining compounds stated. which distinguishes between all 4 compounds
Describing subsequent organic test on product Tests must include reagent and observation which identifies
(unnecessary) - limits to lower mark in level compound(s)
-COOH
Level 2 All stages are covered but stage(s) may be incomplete
a) NaHCO3 / Na2CO3 (or correct alternative)
or may contain inaccuracies
3-4 marks b) effervescence /gas turns limewater milky
OR two stages are covered and are generally correct
c) K and /or M but not L and/or N
and virtually complete.
-OH and -CHO
Answer is communicated mainly coherently and shows d) acidified K2Cr2O7
a logical progression from Stage 1 to Stages 2 and 3. e) solution turns green
f) K and/or L and/or N but not M
Describing subsequent organic test on product
-CHO
(unnecessary) - limits to lower mark in level
g) Fehlings OR Tollens
h) red ppt OR silver mirror
Level 1 Two stages are covered but stage(s) may be incomplete
i) N only but not K and/or L and/or M
or may contain inaccuracies OR only one stage is
1-2 marks -Br
covered but is generally correct and virtually complete.
j) Silver nitrate
Answer includes isolated statements but these are not k) cream ppt
presented in a logical order. l) L and/or N but not K and/or M

Isolated tests on individual compounds - max LEVEL 2

0 mark Insufficient correct chemistry to gain a mark. Isolated tests not linked to any compound – max LEVEL 1
Penalise observation if deduction wrong, but allow
observation if deduction incomplete

23 of 32
 PMT

MARK SCHEME – A-LEVEL CHEMISTRY – 7405/2 – JUNE 2017

Alternative tests

-COOH -COOH -OH only

a) named alcohol & H2SO4 a) named indicator m) named carboxylic acid & H2SO4
b) sweet smell (of ester) b) correct colour n) sweet smell (of ester)
c) K and /or M but not L and/or N c) K and /or M but not L and/or N o) K and/or L but not M and /or N

H CH 3 CH 3 CH 3

H 3C C COOH H 3C C CH 2OH H 3C C COOH H 3C C CHO

OH Br H Br

Test Tests
K L M N
for

a) NaHCO3 / Mg / Indicator KM  ×  ×

d) K2Cr2O7 / H+ KLN   × 

g) Fehlings / Tollens N × × × 

j) AgNO3 see Note * LN ×  × 

a) named alcohol & H2SO4 KM  ×  ×

m) named carboxylic acid & KL   × ×

H2SO4
Note * allow NaOH then HNO3, AgNO3 as one test; but treat NaOH, AgNO3 without acid as incomplete,so can mark on.

24 of 32
 PMT

MARK SCHEME – A-LEVEL CHEMISTRY – 7405/2 – JUNE 2017

Question Answers Mark Additional Comments/Guidance

Allow H2SO4 + HNO3 → NO2+ + HSO4– + H2O

08.1 HNO3 + 2H2SO4 → NO2+ +
+ H3O + 2HSO4– 1 Allow a combination of equations which produce NO2+
Penalise equations which produce SO42–

Electrophilic substitution. 1 Ignore nitration

M1 M3 M1 Arrow from inside hexagon to N or + on N (Allow NO2+)

H
O 2N O2N M2 Structure of intermediate
NO 2
NO2  horseshoe centred on C1 and must not extend beyond
C2 and C6, but can be smaller
 + in intermediate not too close to C1 (allow on or “below”
M2 a line from C2 to C6)
08.2
3 M3 Arrow from bond into hexagon (Unless Kekule)
OR Kekule  Allow M3 arrow independent of M2 structure
 + on H in intermediate loses M2 not M3
M1 M3

O 2N O2 N
+ H
NO2
NO 2

M2

08.3 D 1

(Balance between) solubility in moving phase and retention by OR (relative) affinity for stationary/solid and
08.4 1
stationary phase mobile/liquid/solvent (phase)

25 of 32
 PMT

MARK SCHEME – A-LEVEL CHEMISTRY – 7405/2 – JUNE 2017

08.5 Solvent depth must be below start line 1 Ignore safety

1,2- is more polar OR 1,4- is less polar 1

M2 dependent on correct M1
OR 1,2 is polar, 1,4- is non-polar
If M1 is blank then read explanation for possible M1 and M2
1,4- ( or Less/non polar is) less attracted to (polar) plate / 1
08.6
stationary phase / solid
OR (Less/non polar is) more attracted to / more soluble in
(non-polar) solvent / mobile phase / hexane Allow converse argument for 1,2

No CE = 0
Yes - mark on but there is NO MARK FOR YES
Mark independently following yes
08.7 Solvent (more) polar or ethyl ethanoate is polar 1
Polar isomer more attracted to / more soluble in / stronger 1 Penalise bonded to mobile phase in M2
affinity to the solvent (than before)

Total 12

26 of 32
 PMT

MARK SCHEME – A-LEVEL CHEMISTRY – 7405/2 – JUNE 2017

Question Answers Mark Additional Comments/Guidance

X – base 1 Ignore organic

09.1 Any mention of sugar in either loses that mark
Y – phosphate (group) 1

If not Thymine CE=0

H Ignore lp on N and O
N N H O CH3 Don’t penalise non-linear H bonds
on RHS of thymine – allow with or without H or  [DNA
N N H N
strand]
[DNA strand]
N N
09.2
O (H) 2

Correct structure scores 2, penalise by 1 each error in

 structure of thymine
 orientation of thymine
 hydrogen bonding

Total 4

27 of 32
 PMT

MARK SCHEME – A-LEVEL CHEMISTRY – 7405/2 – JUNE 2017

Question Answers Mark Additional Comments/Guidance

10.1 Z-2-methylpent-2-en (-1-) oic acid 1 Ignore missing hyphens or extra commas, spaces, hyphens

10.2 C6H10O2 + 7½ O2  6CO2 + 5H2O M1 Allow multiple

Volume of CO2 formed = 180 cm3 M2 If incorrect volume:155 gives 125mg / 335 gives 270mg
could score M1,M3,M4 – max 3

If incorrect volume from AE then penalise M2 and mark on

(Final answer is 0.806 x their volume)

Mol carbon dioxide = pV/RT = 105000 × (180 × 10-6) M3 If unit error in p, V or T lose M3 and M5
8.31 × 298 If incorrect rearrangement lose M3 and M5
= 7.632 × 10-3 If both errors seen then no further marks

Mol P, C6H10O2 used = 7.632 × 10-3 / 6 = 1.272 × 10-3 M4 M3 divided by 6 If wrong no further marks

Mass P used = 1.272 × 10-3 × 114(.0) g

M5 Mark for answer (allow ans to 2 sf)
= 145 mg
Check chemical equation before awarding final mark

28 of 32
 PMT

MARK SCHEME – A-LEVEL CHEMISTRY – 7405/2 – JUNE 2017

H 3C

Mark independently
COOH M1
COOH
Apply the list principle
OR H3 C

Fig 4: IR OH (acid) peak (2500-3000cm-1) present M2 Ignore C=O signal at 1750 cm-1
10.3
Fig 5:13C NMR 4 peaks so 4 (non-equivalent) environments
Allow correct Fig 4 answers in Fig 5 and converse
Or Peak at 160-185 (show C=O) in (esters or) acids
M3
Or Peak at 40-50 (show R-CO-CH) presence of carbonyl
Both M2 & M3 can be awarded on the spectra

R has 4 C next to C=O S has 2 C next to C=O M1 M1 for structural point

in range  = 20-50 M2 M2 for resulting peak in spectra
R has two peaks and S only one peak in this range
Or R has more peaks (allowed if no numbers given)

OR
10.4

S has a -C(H2)-C(H3) R does not M1

S has one peak in range  = 5-40 R does not M2
/ lowest peak for S is lower than lowest for R
M3
(Both have) three peaks

29 of 32
 PMT

MARK SCHEME – A-LEVEL CHEMISTRY – 7405/2 – JUNE 2017

R Both singlets M1
M2
S has triplet and a quartet
OR
R CH3/peak at 2.1-2.6 is a singlet M1
S CH3/peak at 0.7-1.2 is a triplet M2
10.5
OR
R CH2/peak at 2.1-2.6 is a singlet M1
M2
S CH2/peak at 2.1-2.6 is a quartet
(Both have) two peaks M3

H 3C O O

CH 3 O CH 3 O

O C (CH 2)3 C C (CH 2) 3 C O

10.6 H OR H
Must have trailing bonds
1
Ignore brackets and n
O CH 3

C O C (CH 2 )3

OR H

condensation 1 Ignore esterification

30 of 32
 PMT

MARK SCHEME – A-LEVEL CHEMISTRY – 7405/2 – JUNE 2017

COOCH2CH3 M1 Must have trailing bonds

Ignore brackets and n
CH2 C

CH3 M3 dependent on correct or close M2

Strong / non-polar C-C bonds (in the chain) M2

cannot be attacked by nucleophiles/acids/cannot be
hydrolysed. M3
10.7 OR
Only polar ester group M2

Can be attacked by nucleophiles/acids/can be hydrolysed M3

Allow 1 mark for in (polar) ester link in side chain/not in main

chain therefore polymer chain not broken

Total 21

31 of 32
 PMT

MARK SCHEME – A-LEVEL CHEMISTRY – 7405/2 – JUNE 2017

Question Answers Mark Additional Comments/Guidance

(Strength depends on availability of) lone pair on N (atom) M1
E N (next to ring): (lp) delocalised into ring M2
(lp) less available (to donate to or to accept a H+) M3
11.1 F or G: N (next to alkyl): (positive) inductive effect/electrons
M4
pushed to N
(lp) more available (to donate to or to accept a H+) M5
order of increasing base strength E<G<F M6 Or F is most basic and E is least basic

Intermediate compounds
Product of step 1 C6H5CH2Cl 1 Allow C6H5CH2Br
Product of step 2 C6H5CH2CN 1
In steps 2 and 3, only allow marks for
reagents/conditions if intermediate compounds are
Reagents/conditions correct or close.
Step 1
11.2 Cl2 & UV 1 Allow Br2 & UV

Step 2
Ignore temperature
KCN alcoholic & aq (both reqd) 1

Step 3 Allow LiAlH4 in (dry) ether – (with acid CE, followed by acid
allow)
H2 / Ni or Pt or Pd 1
Not NaBH4 and not Sn/HCl or Fe/HCl
Total 11

32 of 32