Please write clearly in block capitals.
Centre number Candidate number
AS
CHEMISTRY
Surname
Forename(s)
Candidate signature
I declare this is my own work.
7404/2
Paper 2 Organic and Physical Chemistry
AS Mark scheme
CHEMISTRY June 2026
Paper 2 Organic and Physical Chemistry Version: 1.0 Final
Tuesday 19 May 2026 Morning Time allowed: 1 hour 30 minutes
Materials
For Examiner’s Use
For this paper you must have:
• the Periodic Table/Data Sheet, provided as an insert (enclosed) Question Mark
• a ruler with millimetre measurements 1
• a scientific calculator, which you are expected to use where appropriate. 2
3
Instructions
• Use black ink or black ball-point pen. 4
• Fill in the boxes at the top of this page. 5
• Answer all questions.
6
• You must answer the questions in the spaces provided. Do not write outside
the box around each page or on blank pages. Section B
• If you need extra space for your answer(s), use the lined pages at the end of TOTAL
this book. Write the question number against your answer(s).
• All working must be shown.
• Do all rough work in this book. Cross through any work you do not
want to be marked.
Information
• The marks for questions are shown in brackets.
• The maximum mark for this paper is 80.
Advice
• You are advised to spend 65 minutes on Section A and 25 minutes on Section B.
*Jun *
IB/M/Jun26/G4003/V6 7404/2
, 2
MARK SCHEME – AS CHEMISTRY – 7404/2 – JUNE 2026
Do not write
outside the
Section A box
Mark schemes are prepared by the Lead Assessment Writer and considered, together with the relevant
Answer all questions in this section.
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’
0 1 This question is about the decomposition of methane gas.
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
Figure 1 shows the Maxwell–Boltzmann distribution of molecular energies for
answers not already covered by the mark scheme are discussed and legislated for. If, after the
10 mol of methane gas in a container of fixed volume.
standardisation process, associates encounter unusual answers which have not been raised they are
required to refer these to the Lead Examiner.
Figure 1
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.
No student should be disadvantaged on the basis of their gender identity and/or how they refer to the
gender identity of others in their exam responses.
A consistent use of ‘they/them’ as a singular and pronouns beyond ‘she/her’ or ‘he/him’ will be credited in
exam responses in line with existing mark scheme criteria.
Further copies of this mark scheme are available from
0 1 . 1 Label the y-axis on Figure 1.
[1 mark]
0 1 . 2 The pressure of the methane in the container is increased by adding a further
10 mol of methane.
The temperature remains constant.
Sketch a curve on Figure 1 to show the new distribution of molecular energies.
[2 marks]
information
retains the on all its publications. H r, registered schools/colleges for are permitted to copy material from this booklet for their own
al use, wit ing important exception: cannot give permission to school ges to photocopy any material that is acknowledged to a third
party even for internal use within the centre.
and its licensors. All rights reserved.
*02*
2
IB/M/Jun26/7404/2
, 3
MARK SCHEME – AS CHEMISTRY – 7404/2 – JUNE 2026
Do not write
outside the
0 1 . 3 Methane decomposes into carbon and hydrogen at 1200 °C box
CH4(g) → C(s) + 2 H2(g)
AS and A-level Chemistry
Explain why the rate of decomposition increases at higher pressure. Mark Scheme Instructions for Examiners
[2 marks]
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
0 1 . 4 The rate of decomposition can also be increased by adding a catalyst. 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
The activation energy for the uncatalysed reaction is shown as Ea on Figure 1. 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
Label Figure 1 with an X to show the activation energy for the catalysed reaction. consequential marking needs to be considered in a calculation; or the answer may be on the
[1 mark] 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
0 1 . 5 straightforward and consistent.
Table 1 shows some enthalpy change data.
The use of M1, M2, M3 etc in the right-hand column refers to the marking points in the order in
Table 1 which they appear in the mark scheme. So, M1 refers to the first marking point, M2 the second
marking point etc.
ΔH / kJ mol–1
2. Emboldening
CH4(g) → C(s) + 2 H2(g) +76 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
Bond enthalpy for H–H +436 potential mark.
2.2 A bold and is used to indicate that both parts of the answer are required to award the
C(s) → C(g) +715 mark.
2.3 Alternative answers acceptable for a mark are indicated by the use of OR. Different terms
Use the data in Table 1 to calculate the mean C–H bond enthalpy in methane. in the mark scheme are shown by a / ; eg allow smooth / free movement.
[2 marks]
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.
Mean C–H bond enthalpy kJ mol–1 However, responses considered to be neutral (often prefaced by ‘Ignore’ in the mark
scheme) are not penalised.
Turn over ►
*03*
3
IB/M/Jun26/7404/2
, 4
MARK SCHEME – AS CHEMISTRY – 7404/2 – JUNE 2026
Do not write
outside the
0 1 . 6 State why the mean bond enthalpy for the C–H bond calculated in Question 01.5 is box
different from the mean value for the C–H bond found in data books.
[1 mark]
For example, in a question requiring 2 answers for 2 marks:
Incorrect
Correct answers (ie
Mark (2) Comment
answers incorrect rather
than neutral)
0 1 . 7 1 0 1
Hydrogen obtained from the decomposition of methane can be used as a fuel.
They have not exceeded the maximum
Table 2 shows data about the use of methane and hydrogen as fuels. 1 1 1 number of responses so there is no
penalty.
Table 2 They have exceeded the maximum number
1 2 0 of responses so the extra incorrect
response cancels the correct one.
H2(g) CH4(g)
2 0 2
Enthalpy of combustion / kJ mol–1 –286 –890 2 1 1
2 2 0
Energy density / kJ g–1 143 To be calculated
3 0 2 The maximum mark is 2
The incorrect response cancels out one of
3 1 1 the two correct responses that gained
Calculate the energy density of methane. credit.
[1 mark]
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
Energy density of methane kJ g–1 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.
*04*
4
IB/M/Jun26/7404/2
Centre number Candidate number
AS
CHEMISTRY
Surname
Forename(s)
Candidate signature
I declare this is my own work.
7404/2
Paper 2 Organic and Physical Chemistry
AS Mark scheme
CHEMISTRY June 2026
Paper 2 Organic and Physical Chemistry Version: 1.0 Final
Tuesday 19 May 2026 Morning Time allowed: 1 hour 30 minutes
Materials
For Examiner’s Use
For this paper you must have:
• the Periodic Table/Data Sheet, provided as an insert (enclosed) Question Mark
• a ruler with millimetre measurements 1
• a scientific calculator, which you are expected to use where appropriate. 2
3
Instructions
• Use black ink or black ball-point pen. 4
• Fill in the boxes at the top of this page. 5
• Answer all questions.
6
• You must answer the questions in the spaces provided. Do not write outside
the box around each page or on blank pages. Section B
• If you need extra space for your answer(s), use the lined pages at the end of TOTAL
this book. Write the question number against your answer(s).
• All working must be shown.
• Do all rough work in this book. Cross through any work you do not
want to be marked.
Information
• The marks for questions are shown in brackets.
• The maximum mark for this paper is 80.
Advice
• You are advised to spend 65 minutes on Section A and 25 minutes on Section B.
*Jun *
IB/M/Jun26/G4003/V6 7404/2
, 2
MARK SCHEME – AS CHEMISTRY – 7404/2 – JUNE 2026
Do not write
outside the
Section A box
Mark schemes are prepared by the Lead Assessment Writer and considered, together with the relevant
Answer all questions in this section.
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’
0 1 This question is about the decomposition of methane gas.
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
Figure 1 shows the Maxwell–Boltzmann distribution of molecular energies for
answers not already covered by the mark scheme are discussed and legislated for. If, after the
10 mol of methane gas in a container of fixed volume.
standardisation process, associates encounter unusual answers which have not been raised they are
required to refer these to the Lead Examiner.
Figure 1
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.
No student should be disadvantaged on the basis of their gender identity and/or how they refer to the
gender identity of others in their exam responses.
A consistent use of ‘they/them’ as a singular and pronouns beyond ‘she/her’ or ‘he/him’ will be credited in
exam responses in line with existing mark scheme criteria.
Further copies of this mark scheme are available from
0 1 . 1 Label the y-axis on Figure 1.
[1 mark]
0 1 . 2 The pressure of the methane in the container is increased by adding a further
10 mol of methane.
The temperature remains constant.
Sketch a curve on Figure 1 to show the new distribution of molecular energies.
[2 marks]
information
retains the on all its publications. H r, registered schools/colleges for are permitted to copy material from this booklet for their own
al use, wit ing important exception: cannot give permission to school ges to photocopy any material that is acknowledged to a third
party even for internal use within the centre.
and its licensors. All rights reserved.
*02*
2
IB/M/Jun26/7404/2
, 3
MARK SCHEME – AS CHEMISTRY – 7404/2 – JUNE 2026
Do not write
outside the
0 1 . 3 Methane decomposes into carbon and hydrogen at 1200 °C box
CH4(g) → C(s) + 2 H2(g)
AS and A-level Chemistry
Explain why the rate of decomposition increases at higher pressure. Mark Scheme Instructions for Examiners
[2 marks]
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
0 1 . 4 The rate of decomposition can also be increased by adding a catalyst. 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
The activation energy for the uncatalysed reaction is shown as Ea on Figure 1. 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
Label Figure 1 with an X to show the activation energy for the catalysed reaction. consequential marking needs to be considered in a calculation; or the answer may be on the
[1 mark] 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
0 1 . 5 straightforward and consistent.
Table 1 shows some enthalpy change data.
The use of M1, M2, M3 etc in the right-hand column refers to the marking points in the order in
Table 1 which they appear in the mark scheme. So, M1 refers to the first marking point, M2 the second
marking point etc.
ΔH / kJ mol–1
2. Emboldening
CH4(g) → C(s) + 2 H2(g) +76 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
Bond enthalpy for H–H +436 potential mark.
2.2 A bold and is used to indicate that both parts of the answer are required to award the
C(s) → C(g) +715 mark.
2.3 Alternative answers acceptable for a mark are indicated by the use of OR. Different terms
Use the data in Table 1 to calculate the mean C–H bond enthalpy in methane. in the mark scheme are shown by a / ; eg allow smooth / free movement.
[2 marks]
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.
Mean C–H bond enthalpy kJ mol–1 However, responses considered to be neutral (often prefaced by ‘Ignore’ in the mark
scheme) are not penalised.
Turn over ►
*03*
3
IB/M/Jun26/7404/2
, 4
MARK SCHEME – AS CHEMISTRY – 7404/2 – JUNE 2026
Do not write
outside the
0 1 . 6 State why the mean bond enthalpy for the C–H bond calculated in Question 01.5 is box
different from the mean value for the C–H bond found in data books.
[1 mark]
For example, in a question requiring 2 answers for 2 marks:
Incorrect
Correct answers (ie
Mark (2) Comment
answers incorrect rather
than neutral)
0 1 . 7 1 0 1
Hydrogen obtained from the decomposition of methane can be used as a fuel.
They have not exceeded the maximum
Table 2 shows data about the use of methane and hydrogen as fuels. 1 1 1 number of responses so there is no
penalty.
Table 2 They have exceeded the maximum number
1 2 0 of responses so the extra incorrect
response cancels the correct one.
H2(g) CH4(g)
2 0 2
Enthalpy of combustion / kJ mol–1 –286 –890 2 1 1
2 2 0
Energy density / kJ g–1 143 To be calculated
3 0 2 The maximum mark is 2
The incorrect response cancels out one of
3 1 1 the two correct responses that gained
Calculate the energy density of methane. credit.
[1 mark]
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
Energy density of methane kJ g–1 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.
*04*
4
IB/M/Jun26/7404/2
