AQA A-level CHEMISTRY Paper 1 MARK SCHEME 2024: Inorganic and Physical Chemistry, Exams of Chemistry

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A level

AQA

A-level

CHEMISTRY

Paper 1 Inorganic and Physical Chemistry

Mark scheme

June 2024

Version: 1.0 Final

246A74051/MS

AS and 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.

For example, in a question requiring 2 answers for 2 marks:

Correct

answers

Incorrect

answers (ie

incorrect rather

than neutral)

Mark (2) Comment

They have not exceeded the maximum

number of responses so there is no

penalty.

They have exceeded the maximum number

of responses so the extra incorrect

response cancels the correct one.

3 0 2 The maximum mark is 2

The incorrect response cancels out one of

the two correct responses that gained

credit.

Two incorrect responses cancel out the two

marks gained.

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.

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.

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

(eg 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:

By way of illustration, the following would apply.

allowed allowed not allowed not allowed not allowed

allowed allowed allowed allowed not allowed

not allowed not allowed not allowed not allowed not allowed

not allowed not allowed not allowed not allowed not allowed

 Representation^ of^ CH 2 by^ CH 2 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)

CH 3 COH for ethanal

CH 3 CH 2 HO for ethanol

OHCH 2 CH 3 for ethanol

C 2 H 6 O for ethanol

CH 2 CH 2 for ethene

CH 2. CH 2 for ethene

CH 2 : CH 2 for ethene

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

the structures.

CH 2 = CH 2 for ethene, H 2 C=CH 2

CH 3 CHOHCH 3 for propan- 2 - ol, CH 3 CH(OH)CH 3

 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 (eg 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.

Unnecessary but not wrong numbers will not be penalised such as the number ‘2’ in 2 -

methylpropane or the number ‘1’ in 2 - chlorobutan- 1 - oic acid.

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)

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

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.

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.

Question (^) Answers Additional comments/Guidelines Mark

B/ Boron

any 2 from:

protons in the centre of the atom/nucleus

electrons are in shells/energy levels (around the nucleus)

neutrons in the centre of the atom/nucleus

most of the atom is empty space/most of mass in nucleus

(3 x AO1)

Question Answers Additional comments/Guidelines Mark

Definition

Average / mean mass of 1 atom (of an element) (1)

1/12 mass of one atom of

12 C (1)

Or

Average / mean mass of atoms of an element

1/12 mass of one atom of

12 C

11

Or

I has similar chemistry/chemical properties to other Group 7

elements

Question Answers Additional comments/Guidelines Mark

Te(g) + e

• → Te

(g) + 2 e

Or

Te(g) → Te

(g) + e

(1 x AO1)

Question Answers Additional comments/Guidelines Mark

M1 v = d^ = 4.17 × 10

6 (m s

• 1 )

t

2 −

M2 m =

2KE×t or m =

2KE or

2 𝑥 1.88 𝑥 10

d^2 v^2 (4.17 𝑥 106 )

2

M3 m = 2.16 x 10

• 25 to 2.17 × 10 - 25 (kg)

M4 mass of 1 mole of ions = L × 1000 × M3 = 130.4 (g)

M5 y = 130 or 131

M4 Allow 130 to 131 (3 or more significant

figures)

M5 Must be an integer

(4 x AO2,

1 x AO3)

Question Answers Additional comments/Guidelines Mark

01.5 The KE of

126 Te

is the same as the KE of

124 Te

(1 x AO1)

Question Answers Additional comments/Guidelines Mark

To prevent reaction with carbon dioxide (in the air)

OR

To prevent evaporation (of water/from solution)

Allow so flask can inverted/shaken (to ensure

homogeneous mixture)

Ignore contamination

(1 x AO2)

Question Answers Additional comments/Guidelines Mark

Answer C 1

(1 x AO3)

Question Answers Additional comments/Guidelines Mark

M1 Sr(OH) 2 + 2 HCl → SrCl 2 + 2 H 2 O

M2 32.43 (cm

3 )

M3 n HCl in mean titre = 3.24(3) × 10

• 3 mol

M4 n Sr(OH) 2 in 25 cm

3 = 1.62 × 10

• 3 mol

M5 n Sr(OH) 2 in 100 cm

3 of solution = 6.48 × 10

• 3 mol

M6 mass = (6.48×

• 3 mol x 121.6) = 0.788 (g per 100 cm

3

solution)

M1 Equation

M2 allow 32.

M3 allow 0.1 x M2 ÷ 1000

M4 allow M3 ÷ 2

M5 allow M4 × 4

M6 allow = M5 × 121.

M6 allow 0.

allow M5 and M6 in either order

(6 x AO2)

Question Answers Additional comments/Guidelines Mark

This question is marked using levels of response. Refer to

the Mark Scheme Instructions for Examiners for guidance on

how to mark this question.

Level 3

5 – 6 marks

All stages are covered and the description of each stage is

generally correct and virtually complete.

Answer is communicated coherently and shows a logical

progression from stage 1 to stage 2 and stage 3.

Level 2

3 – 4 marks

All stages are covered but the description of each stage may

be incomplete or may contain inaccuracies OR two stages are

covered and the explanations are generally correct and

virtually complete.

Answer is mainly coherent and shows progression from stage

1 to stage 2 and/or stage 3.

Level 1

1 – 2 marks

Two stages are covered but the description of each stage

may be incomplete or may contain inaccuracies, OR only one

stage is covered but the explanation is generally correct and

virtually complete.

Answer includes isolated statements and these are presented

in a logical order.

Level 0

0 marks

Insufficient correct chemistry to gain a mark.

Indicative Chemistry Content

stage 1

1a labelled axes

and concentration (of S 2 O

2 – ions) decreasing with 8

time (ignore units)

1b downwards curve of reducing steepness

(2 × AO1,

2 x AO2, 2

x AO3)

stage 2 explanation

2a (reaction slow) because S 2 O 8 and I repel/high

2 – –

Ea

Or

(reaction slow) because two negative ions repel/high

Ea

2 –

2b Fe

2+ attracts the S 2 O 8 so lower Ea

Or 2 –

Fe

2+ and S 2 O 8 oppositely charged so lower Ea

2c Iron/Fe has a variable oxidation state

Or

Fe

2+ oxidised to Fe

3+

Or

Fe

2+  Fe

3+

• e

stage 3 equations

2 – 2 – 3+

3a 2 Fe

2+

• S 2 O 8 → 2 SO 4 + 2 Fe

3b 2 Fe

3+

+ 2 I

• → 2 Fe

2+

+ I 2

3c S 2 O 8 + 2 I → 2 SO 4 + I 2

2 – – 2 –

allow equations with hexaaqua ions