Cambridge International AS & A Level

CHEMISTRY 9701 / 34
Paper 3 Advanced Practical Skills 2 October/November 2024
MARK SCHEME
Maximum Mark: 40

Published

This mark scheme is published as an aid to teachers and candidates, to indicate the requirements of the
examination. It shows the basis on which Examiners were instructed to award marks. It does not indicate the
details of the discussions that took place at an Examiners’ meeting before marking began, which would have
considered the acceptability of alternative answers.

Mark schemes should be read in conjunction with the question paper and the Principal Examiner Report for
Teachers.

Cambridge International will not enter into discussions about these mark schemes.

Cambridge International is publishing the mark schemes for the October/November 2024 series for most
Cambridge IGCSE, Cambridge International A and AS Level components, and some Cambridge O Level
components.

This document consists of 10 printed pages.

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9701 / 34 Cambridge International AS & A Level – Mark Scheme October/November 2024
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Generic Marking Principles

These general marking principles must be applied by all examiners when marking candidate answers. They should be applied alongside the
specific content of the mark scheme or generic level descriptions for a question. Each question paper and mark scheme will also comply with these
marking principles.

GENERIC MARKING PRINCIPLE 1:

Marks must be awarded in line with:

• the specific content of the mark scheme or the generic level descriptors for the question
• the specific skills defined in the mark scheme or in the generic level descriptors for the question
• the standard of response required by a candidate as exemplified by the standardisation scripts.

GENERIC MARKING PRINCIPLE 2:

Marks awarded are always whole marks (not half marks, or other fractions).

GENERIC MARKING PRINCIPLE 3:

Marks must be awarded positively:

• marks are awarded for correct / valid answers, as defined in the mark scheme. However, credit is given for valid answers which go beyond
the scope of the syllabus and mark scheme, referring to your Team Leader as appropriate
• marks are awarded when candidates clearly demonstrate what they know and can do
• marks are not deducted for errors
• marks are not deducted for omissions
• answers should only be judged on the quality of spelling, punctuation and grammar when these features are specifically assessed by the
question as indicated by the mark scheme. The meaning, however, should be unambiguous.

GENERIC MARKING PRINCIPLE 4:

Rules must be applied consistently, e.g. in situations where candidates have not followed instructions or in the application of generic level
descriptors.

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GENERIC MARKING PRINCIPLE 5:

Marks should be awarded using the full range of marks defined in the mark scheme for the question (however; the use of the full mark range may
be limited according to the quality of the candidate responses seen).

GENERIC MARKING PRINCIPLE 6:

Marks awarded are based solely on the requirements as defined in the mark scheme. Marks should not be awarded with grade thresholds or
grade descriptors in mind.

Science-Specific Marking Principles

1 Examiners should consider the context and scientific use of any keywords when awarding marks. Although keywords may be present, marks
should not be awarded if the keywords are used incorrectly.

2 The examiner should not choose between contradictory statements given in the same question part, and credit should not be awarded for
any correct statement that is contradicted within the same question part. Wrong science that is irrelevant to the question should be ignored.

3 Although spellings do not have to be correct, spellings of syllabus terms must allow for clear and unambiguous separation from other
syllabus terms with which they may be confused (e.g. ethane / ethene, glucagon / glycogen, refraction / reflection).

4 The error carried forward (ecf) principle should be applied, where appropriate. If an incorrect answer is subsequently used in a scientifically
correct way, the candidate should be awarded these subsequent marking points. Further guidance will be included in the mark scheme
where necessary and any exceptions to this general principle will be noted.

5 ‘List rule’ guidance

For questions that require n responses (e.g. State two reasons …):

• The response should be read as continuous prose, even when numbered answer spaces are provided.
• Any response marked ignore in the mark scheme should not count towards n.
• Incorrect responses should not be awarded credit but will still count towards n.
• Read the entire response to check for any responses that contradict those that would otherwise be credited. Credit should not be
awarded for any responses that are contradicted within the rest of the response. Where two responses contradict one another, this
should be treated as a single incorrect response.
• Non-contradictory responses after the first n responses may be ignored even if they include incorrect science.

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6 Calculation specific guidance

Correct answers to calculations should be given full credit even if there is no working or incorrect working, unless the question states ‘show
your working’.

For questions in which the number of significant figures required is not stated, credit should be awarded for correct answers when rounded
by the examiner to the number of significant figures given in the mark scheme. This may not apply to measured values.

For answers given in standard form (e.g. a  10n) in which the convention of restricting the value of the coefficient (a) to a value between 1
and 10 is not followed, credit may still be awarded if the answer can be converted to the answer given in the mark scheme.

Unless a separate mark is given for a unit, a missing or incorrect unit will normally mean that the final calculation mark is not awarded.
Exceptions to this general principle will be noted in the mark scheme.

7 Guidance for chemical equations

Multiples / fractions of coefficients used in chemical equations are acceptable unless stated otherwise in the mark scheme.

State symbols given in an equation should be ignored unless asked for in the question or stated otherwise in the mark scheme.

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Question Answer Marks

1(a) I All the following data are recorded 1

• two burette readings and titre for the rough titration
• initial and final burette readings for two (or more) accurate titrations

II Correct headings and units shown in the accurate titration table and titre values recorded for accurate titrations 1
• initial / start and (burette) reading / volume
• final / end and (burette) reading / volume
• titre or volume / FB 2 and used / added
• unit: / cm3 or (cm3) or in cm3 (for each heading)
or cm3 unit given for each volume recorded

Ill All accurate burette readings are recorded to the nearest 0.05 cm3. 1

lV: The final accurate titre recorded is within 0.10 cm3 of any other accurate titre 1

Award accuracy Q marks as follows: 1

V Award if  ⩽ 0.60 cm3

VI Award if  ⩽ 0.40 cm3

VII Award if  ⩽ 0.20 cm3

If Supervisor’s mean titre > 50.00 cm3 then use the tolerances (0.80, 0.50, 0.30 cm3)
If Supervisor’s mean titre < 10.00 cm3 then halve the tolerances (0.30, 0.20, 0.10 cm3)
If Supervisor’s mean titre < 5.00 cm3 then use the tolerances (0.15, 0.10, 0.05 cm3)

1(b) Correctly calculates the mean titre to 2 decimal places. 1

• Candidate must take the average of two (or more) accurate titres that are within a total spread of not more than
0.20 cm3.
• Working / explanation must be shown or ticks must be put next to the two (or more) accurate readings selected.
• The mean should be quoted to 2 d.p. and be rounded to nearest 0.01 cm3. (e.g. 26.675 cm3 must be rounded to
26.68 cm3).

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Question Answer Marks

1(c)(i) Answers to all 3 parts of (c)(ii) and (c)(iii) quoted to 3 or 4 significant figures. 1

1(c)(ii) M1: Correctly calculates 2

amount of S2O32– = (b) / 1000  0.0100 (1)

M2: Correct use of n(S2O32–)

amount of I2 = ans / 2  150 / 25 (1)

1(c)(iii) Correct use of 1

amount of I2 from (c)(ii) / 0.150
or
(M1 from (c)(ii) / 2)  (1000 / 25)

1(c)(iv) M1: Correctly calculates 2

0.05(00)
and correctly uses
(0.0500 – (c)(iii)) / 80

M2: Units
mol dm–3 s–1

1(d) Release of iodine from the starch complex is slow at high iodine concentrations 1
Or
A starch-iodine complex / precipitate is formed which does not decompose (during the titration)

1(e) The student is incorrect and one of: 1

• The sodium hydrogencarbonate must be added at 80 s to stop / quench the reaction (by reacting with the acid catalyst)
ORA

• The reaction would continue if the sodium hydrogencarbonate is not added at 80 s

• The sample can be removed before 80 s as the reaction only stops when the sodium hydrogencarbonate is added.

• The sodium hydrogencarbonate reacts with the acid which is the catalyst.

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Question Answer Marks

2(a) I 4 unambiguous headings for balance readings and correct units 1

• (Mass of) crucible + lid
• (Mass of) crucible, lid and FB 4 (or ‘contents before heating’)
• (Mass of) crucible, lid and contents / residue after first heating
• (Mass of) crucible, lid and contents / residue after second heating
Units with all required headings: / g, (g), in g (or g with every entry)

II Recording of all weighings 1

• All 4 weighings recorded to same number of decimal places (two or three).

• Fourth weighing is within +0.02 and –0.05 g of third weighing.

III Calculated masses 1

Correct subtractions to give masses of FB 4 and residue
and
both headings clearly labelled
and
both answers to min 2 sf.

For assessment of accuracy (Q) marks

Calculate the candidate’s mass ratio (to 2 d.p.) = mass FB 4 / mass of residue.

If 4th weighing > 3rd weighing, use lower value to calculate the mass of residue.

Award accuracy Q marks as follows: 2

Award IV if 1.07 ≤ ratio ≤ 1.27
Award V if 1.12 ≤ ratio ≤ 1.22

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Question Answer Marks

2(b) M1 Correctly calculates amount of water 2

amount of H2O = (mass of FB 4 – mass of residue) / 18
and answer to 2–4 s.f.

M2 Correct use of amount of water

Mr of MA2 = 2  mass of residue / amount of H2O
and
answer to 2–4 s.f.

2(c) Identification of A− 2
• use of (aqueous) silver nitrate / AgNO3
• white precipitate formed
• precipitate is soluble in (excess aqueous) ammonia
• A− is identified as Cl − / chloride

2(d) Identification of M2+ 1

Shows working: ((b) – 71)

and

selects M from Group 2 with closest Ar

and

2+ charge on ion

2(e) M1 (Calculated) Mr would be greater 1

and
amount / moles of water is smaller or mass of residue / MA2 is greater

M2 One of: 1
• there are significant / big differences between the Ar s of the elements / metals (in Group 2) owtte

• most of the water was driven off / very little water of crystallisation left owtte

• the calculated Ar (or Mr) is still closest to the same answer

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Question Answer Marks

Q3 FB 6 is KMnO4; FB 7 is CuSO4(aq)

3(a)(i) 2* = 1 mark 1
• (Dark) purple / purple-black solid / crystals (initially)
• (Solid / crystals) jump(s) around the tube / pops / crackles (on heating)
• Black powder / solid / residue (remains)
• (gas) relights a glowing splint
• (gas produced is) oxygen

3(a)(ii) Test 1 1
(forms) purple solution
Or
(water) turns purple (solution)

Test 2 1
(forms) green solution
or
(NaOH) turns green (solution)

3(a)(iii) thermal decomposition / redox 1

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Question Answer Marks

3(b)(i) Observations 5

Test Observations

1 (pale) blue ppt *

+NH3 (ppt) soluble / disappears in excess (NH3)
or solution formed in excess (NH3) *
Deep / dark blue (solution) (with excess) *

black / (dark) green*

+ H2O2 effervescence*
(gas) relights a glowing splint*

2 brown / yellow-brown / yellow solution*

+ KI (off-)white / (pale) brown / yellow-brown
precipitate / solid*

+ Solution / solid / ppt becomes paler owtte*

Na2S2O3 Precipitate partially dissolves or ppt dissolves in
excess (thiosulfate)*

3(b)(ii) M1 Choice of reagent(s) 1

Selects barium chloride / BaCl2 or barium nitrate / Ba(NO3)2
and nitric acid / HNO3 or hydrochloric acid / HCl
OR
Selects (acidified aqueous) potassium manganate(VII) / (H+) & KMnO4

M2 Clear results to show: 1

white ppt (with Ba2+) and insoluble in acid
OR
(KMnO4) remains purple / not decolourised / no change

3(b)(iii) CuSO4 1

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