Cambridge International AS & A Level Chemistry - Paper 4 Mark Scheme May-June 2023, Exams of Chemistry

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Chemistry - 9701 -41 Paper 4 - A Level Structured

Questions Mark Scheme - May -June 2023 AS and A

Level - Cambridge International Examination

Cambridge International AS & A Level

CHEMISTRY 9701/

Paper 4 A Level Structured Questions May/June 2023

MARK SCHEME

Maximum Mark: 100

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 May/June 2023 series for most

Cambridge IGCSE, Cambridge International A and AS Level and Cambridge Pre-U components,

and some Cambridge O Level components.

This document consists of 17 printed pages.

© UCLES 2023 [Turn^ over

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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 descriptors 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.

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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  10

n ) 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) M1 increases (down the group)

M2 radius / size of (cat)ion / M

2+ increases M3 less polarisation / distortion of anion / nitrate ion / NO 3 OR less weakening of N–O / N=O (bond)

1(b) Cu(NO 3 ) 2 CuO + 2NO 2 + ½O 2 1

1(c)

Two correct for one mark, four correct for two marks, six correct for three marks, eight correct

for four marks.

1(d)(i) M1 (a species) that donates more than two lone pairs

M2 to form dative / coordinate bonds to a metal atom or ion

1(d)(ii)

six atoms circled, 2N and 4O from different CO 2

• 1

1(d)(iii) the number of co-ordinate bonds being formed by the metal ion 1

1(d)(iv) ligand exchange 1

1(d)(v) [FeEDTA]

• [CrEDTA] - > [PbEDTA]

2–

highest conc

n lowest conc

n AND K stab of [FeEDTA]

• is highest

copper-

containi

ng

species

formula of copper-

containing species

formed

colour

copper-

containing

formed

A [Cu(H 2 O) 6 ]

2+ (pale) blue

B Cu(H 2 O) 4 (OH) 2 or

Cu(OH) 2

(pale) blue

C [Cu(NH 3 ) 4 (H 2 O) 2 ]

2+ dark blue

D

CuC l 4 yello

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Question Answer Marks

1(e) M1 moles of Cr

3+ = 2.096  10

• in 25.0 cm

3 )

M2 moles of Cr

3+ = 8.384  10

• (in 100.0 cm

3 )

moles of Cr 2 (SO 4 ) 3 nH 2 O = 8.384  10

• / 2 = 4.

 10

• M3 M r of Cr 2 (SO 4 ) 3 nH 2 O = 0.2550 / 4.192 

• = 608.3 n = (608.3 – 392.3) / 18 = 12

1(f) M1  E is different

M2 different frequency (of light) is absorbed

Question Answer Marks

2(a) geometrical / cis-trans AND optical 1

2(b) square planar 1

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Question Answer Marks

2(c)

Two correct for one mark, three correct for two marks, four correct for three marks.

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Question Answer Marks

2(d)(i)

M1 two correct curly arrows

M2 correct dipole

M3 correct structure of intermediate

2(d)(ii) use an excess of ammonia OR limiting amount of oxirane 1

2(d)(iii)

M

M2 elimination / dehydration / condensation

Question Answer Marks

3(a)(i) the power to which the concentration of a reactant is raised in the rate equation 1

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Question Answer Marks

3(a)(ii)

All correct for one mark

3(a)(iii) 1

3(a)(iv)

M1 k = rate / [I

• ]

2 [IO 3 ][H ] = (4.20  10 )/(0.025 0.04x0.015 ) = 7.47  10

• • 2 -2 2 2 6

M2 units = mol

• dm

12 min

3(a)(v) 0.0709 = k 0.12 [H

]

2 0.

2

[H

] = 2.25  10

3(a)(vi) (^) x = 10

2 / 1 = 100^1

3(b) M1 step 1 Fe

3+

• I

• FeI

2+

M2 step 2 FeI

2+

• I

• Fe

2+

• I 2 OR FeI + I FeI 2 AND slowest step = step 2

• 2+ – +

M3 step 3 Fe

3+

• I 2 Fe + I 2 OR FeI 2 + Fe 2Fe + I 2

• 2+ + 3+ 2+

the order of reaction with respect to [IO 3 ]

the order of reaction with respect

to [H

]

the order of reaction with respect

to [I

• ]

the overall order of reaction 5

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Question Answer Marks

4(a) M1 bond angle = 120° AND carbons are sp

2

M2 bonds are formed by end-on-end / head on / head to head / linear overlap of orbitals

M3 bonds are formed by sideways / lateral overlap of p orbitals

4(b)(i)

[1] [1]

4(b)(ii) M1 step 1 (CH 3 ) 2 CHBr and FeBr 3 / A l

Br 3 M2 step 2 conc HNO 3 and

conc H 2 SO 4 M3 step 3 Sn and conc

HC l

4(c) 3,4,5-trimethylphenylamine 1

4(d)

Both correct for one mark

Question Answer Marks

5(a)(i) palladium, platinum and rhodium / Pt, Pd, Rh 1

5(a)(ii) a catalyst in a different state / phase to the reactants / substrate 1

5(b)(i) measure / degree of disorder / randomness of a system

OR the number of possible arrangements of the particles and the energy in a system

compoun

d

number of peaks

observed

W 6

Z 6

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Question Answer Marks

5(b)(ii) M1  S

o = (192.8) + 213.8 – 238.2 – 188.

 S

o = -20.4 (J K

• mol - )

M2  H

o = (–45.9) + (–393.5) – (–101.7) – (–241.8)

 H

o = -95.9 (kJ mol

• )

M3  G

o =  H

o

• T S

o

M4  G

o = –95.9 – (298 –0.0204) = –89.8 (kJ mol

• )

5(c) 4(NH 2 ) 2 CO + 6NO 2 7N 2 + 8H 2 O + 4CO 2 1

5(d) 1

5(e)(i) p K a = –log K a AND pH = –log [H

] 1

5(e)(ii) M1 [H

] = √0.120 2.00  10

• = 4.89(317)  10 -

M2 pH = 2.

5(e)(iii) (^) % ionisation = 4.89  10

• /0.12 100 = 4.1%^1

Question Answer Marks

6(a)(i) carboxylic acid, amine, alkene

Two correct for one mark, three correct for two marks

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Question Answer Marks

6(a)(ii)

optical Two correct for one mark, three correct for

two marks.

6(b)(i) 1

6(b)(ii) hydrolysis 1

6(c)(i) 1

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Question Answer Marks

6(c)(ii)

M1 amide linkage displayed correctly

M2 rest of the structure correct

6(c)(iii) condensation polymers can be hydrolysed 1

Question Answer Marks

7(a) M1 diethylamine > ethylamine >

ethanamide explanation

M2 basicity linked to ability of lone pair on N to accept a proton / H

M3 electron donating ethyl group increases electron density on N / makes lone pair more available for

donation

M4 lone pair of electrons on N is delocalised into C=O group

7(b)(i) M1 resists change in pH

M2 when a small amount of acid or alkali is added

7(b)(ii) M1 H 2 NCH(CH 3 )COOH + H

H 3 N

CH(CH 3 )COOH

M2 H 2 NCH(CH 3 )COOH + OH

• H 2 NCH(CH 3 )COO - + H 2 O

7(c)(i)^1

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Question Answer Marks

7(c)(ii)

M1 displayed peptide bond (between two amino acids)

M2 rest of the structure correct

7(d)

M1 relative positions of the spots drawn

M2 Ala is a zwitterion / neutral / at its isoelectric point (at pH 6) OR ala-glu AND glu are negatively charged

M3 glu has lower M r OR ala-glu has higher M r

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Question Answer Marks

7(e)(i)

Three correct for one mark, six correct for two marks, nine correct for three marks.

7(e)(ii) one extra peak for NH 2 group seen in CDC l 3 , AND H exchanged for D in D 2 O 1

Question Answer Marks

8(a)

All correct for one mark

8(b) The^ energy^ /^ enthalpy^ change when 1 mole^ of gaseous ions^ is dissolved in^ water^^1

8(c)(i) M1 use of correct six numbers only

682.8 178.2 590 1145 111.9 324.

M2 2 used correctly with Br (2 111.9 and 2 324.6)

M3 correct signs and evaluation to give –2170.6 kJ mol

chemical

shift (δ)

splitting

pattern

number of

1 H

atoms

responsible for

the peak

number of

protons on the

adjacent

carbon(s)

double

t

singlet 3 0

4. quarte 1 3

energy change always

positive

always

negativ

e

either

negative

or positive

lattice energy 

enthalpy of

hydration



enthalpy of 

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Question Answer Marks

8(c)(ii) M1 use of correct three numbers only 2170.6 103.1 and 1579

M2 correct signs & evaluation –347 kJ mol

8(c)(iii) M1 Br

• has a smaller ionic radius

M2 Br

• has stronger attractive forces with water molecules