Please check the examination details below before entering your candidate information
Candidate surname Other names
Centre Number Candidate Number
Pearson Edexcel International Advanced Level
Monday 12 January 2026 Mark Scheme (Results)
Afternoon (Time: 1 hour 30 minutes) Paper
reference WCH11/01
January 2026
Chemistry
International Advanced Subsidiary/Advanced Level
UNIT 1: Structure, Bonding and Introduction to
Organic Chemistry
You must have: Total Marks
Scientific calculator Pearson Edexcel International Advanced Subsidiary Level
in Chemistry
Instructions Paper 01: Structure, Bonding and Introduction to Organic
•• Use black ink or ball-point pen. Chemistry
If pencil is used for diagrams/sketches/graphs it must be dark (HB or B). WCH11/01
• Fill in the boxes at the top of this page with your name,
centre number and candidate number.
•• Answer allthequestions.
Answer
questions in the spaces provided
– there may be more space than you need.
Information
•• The total mark for this paper is 80.
The marks for each question are shown in brackets
– use this as a guide as to how much time to spend on each question.
• You will be assessed on your ability to organise and present information, ideas,
descriptions and arguments clearly and logically, including your use of grammar,
punctuation and spelling.
• A Periodic Table is printed on the back cover of this paper.
Advice
• Read each question carefully before you start to answer it.
•• Show all your working in calculations and include units where appropriate.
Try to answer every question.
• Check your answers if you have time at the end. Turn over
P79049APearson Education Ltd.
C:1/1/1/
*P79049A0124*
, SECTION A
Edexcel and BTEC Qualifications
Answer ALL the questions in this section.
DO NOT WRITE IN THIS AREA DO NOT WRITE IN THIS AREA DO NOT WRITE IN THIS AREA
DO NOT WRITE IN THIS AREA DO NOT WRITE IN THIS AREA DO NOT WRITE IN THIS AREA
You should aim to spend no more than 20 minutes on this section. Edexcel and BTEC qualifications are awarded by Pearson, the UK’s
largest awarding body. We provide a wide range of qualifications
For each question, select one answer from A to D and put a cross in the box . If you change including academic, vocational, occupational and specific
your mind, put a line through the box and then mark your new answer with a cross . programmes for employe a
qualifications websites at or .
1 Which property determines the order of elements in the Periodic Table? Alternatively, you c
contact us page at
A first ionisation energy
B relative atomic mass
C number of electrons in the outer shell
D number of protons in the nucleus Pearson: helping people progress, everywhere
(Total for Question 1 = 1 mark)
Pearson aspires to be the world’s leading learning company. Our aim is to
help everyone progress in their lives through education. We believe in every
2 Which atom has the most orbitals that contain a single electron?
kind of learning, for all kinds of people, wherever they are in the world. We’ve
A C been involved in education for over 150 years, and by working across 70
countries, in 100 languages, we have built an international reputation for our
B Cr
commitment to high standards and raising achievement through innovation
C Mn in education. Find out more about how we can help you and your students at:
D N
(Total for Question 2 = 1 mark)
3 The electronic configuration of element X is 1s2 2s2 2p6 3s2 3p4.
What is the formula of the compound formed when X reacts with potassium?
A KX
B K2X
C K3X
D KX2
January 2026
(Total for Question 3 = 1 mark) Question Paper Log Number P79049A
Publication Code WCH11_01_2601_MS
Use this space for any rough working. Anything you write in this space will gain no credit. All the material in this publication is
Pearson Education Ltd
2
*P79049A0224*
, General Marking Guidance
4 Which ion is not isoelectronic with the other ions?
• All candidates must receive the same treatment. Examiners must mark the
A Ti3+
DO NOT WRITE IN THIS AREA DO NOT WRITE IN THIS AREA DO NOT WRITE IN THIS AREA
DO NOT WRITE IN THIS AREA DO NOT WRITE IN THIS AREA DO NOT WRITE IN THIS AREA
first candidate in exactly the same way as they mark the last.
B Ca2+
• Mark schemes should be applied positively. Candidates must be rewarded
C P3– for what they have shown they can do rather than penalised for omissions.
D Cl– • Examiners should mark according to the mark scheme not according to their
(Total for Question 4 = 1 mark) perception of where the grade boundaries may lie.
• There is no ceiling on achievement. All marks on the mark scheme should be
5 Which properties of a cation result in the greatest polarising power? used appropriately.
• All the marks on the mark scheme are designed to be awarded. Examiners
Radius Charge should always award full marks if deserved, i.e. if the answer matches the
A small small mark scheme. Examiners should also be prepared to award zero marks if the
candidate’s response is not worthy of credit according to the mark scheme.
B large large
• Where some judgement is required, mark schemes will provide the principles
C small large
by which marks will be awarded and exemplification may be limited.
D large small • When examiners are in doubt regarding the application of the mark scheme
(Total for Question 5 = 1 mark) to a candidate’s response, the team leader must be consulted.
• Crossed out work should be marked UNLESS the candidate has replaced it
6 The first five ionisation energies of element Z are shown. with an alternative response.
1st 2nd 3rd 4th 5th
13 629
What is the formula of the most stable chloride of Z?
A ZCl4
B ZCl3
C ZCl2
D ZCl
(Total for Question 6 = 1 mark)
7 Which is not a neutralisation reaction?
A Zn + H2SO4 → ZnSO4 + H2
B CuO + 2HCl → CuCl2 + H2O
C NH3 + HNO3 → NH4NO3
D CaCO3 + 2CH3COOH → Ca(CH3COO)2 + H2O + CO2
(Total for Question 7 = 1 mark)
3
*P79049A0324* Turn over
, Using the Mark Scheme
8 A hydrocarbon contains 82.8% carbon by mass.
Examiners should look for qualities to reward rather than faults to penalise. This does
Which could be the molecular formula of the hydrocarbon?
NOT mean giving credit for incorrect or inadequate answers, but it does mean
DO NOT WRITE IN THIS AREA DO NOT WRITE IN THIS AREA DO NOT WRITE IN THIS AREA
DO NOT WRITE IN THIS AREA DO NOT WRITE IN THIS AREA DO NOT WRITE IN THIS AREA
A CH3 allowing candidates to be rewarded for answers showing correct application of
principles and knowledge. Examiners should therefore read carefully and consider
B C2H6 every response: even if it is not what is expected it may be worthy of credit.
C C2H5
The mark scheme gives examiners:
D C4H10 • an idea of the types of response expected
• how individual marks are to be awarded
(Total for Question 8 = 1 mark)
• the total mark for each question
• examples of responses that should NOT receive credit.
9 What is the percentage composition by mass of nitrogen in (NH4)2SO4 ?
/ means that the responses are alternatives and either answer should receive full
A 27.3%
credit.
B 21.2% ( ) means that a phrase/word is not essential for the award of the mark, but helps the
examiner to get the sense of the expected answer.
C 13.6%
D 10.6% Phrases/words in bold indicate that the meaning of the phrase or the actual word is
essential to the answer.
(Total for Question 9 = 1 mark) ecf/TE/cq (error carried forward) means that a wrong answer given in an earlier part of
a question is used correctly in answer to a later part of the same question.
10 What is the total number of ions in 10.0 g of iron(III) sulfate, Fe2(SO4)3 ?
Candidates must make their meaning clear to the examiner to gain the mark. Make
[Data: Molar mass of iron(III) sulfate = 399.9 g mol–1 sure that the answer makes sense. Do not give credit for correct words/phrases which
Avogadro constant (L) = 6.02 × 1023 mol–1] are put together in a meaningless manner. Answers must be in the correct context.
A 1.5 × 1022
Quality of Written Communication
B 3.0 × 1022
C 4.5 × 1022 Questions which involve the writing of continuous prose will expect candidates to:
• write legibly, with accurate use of spelling, grammar and punctuation in order to
D 7.5 × 1022 make the meaning clear
• select and use a form and style of writing appropriate to purpose and to complex
(Total for Question 10 = 1 mark)
subject matter
• organise information clearly and coherently, using specialist vocabulary when
11 What mass of barium chloride, BaCl2 , is needed to make 500 cm3 of a appropriate.
0.100 mol dm–3 solution?
[Data: Ar Ba = 137.3 Cl = 35.5] Full marks will be awarded if the candidate has demonstrated the above abilities.
Questions where QWC is likely to be particularly important are indicated (QWC) in the
A 41.66 g mark scheme, but this does not preclude others.
B 20.83 g
C 10.42 g
D 8.64 g
(Total for Question 11 = 1 mark)
4
*P79049A0424*
Candidate surname Other names
Centre Number Candidate Number
Pearson Edexcel International Advanced Level
Monday 12 January 2026 Mark Scheme (Results)
Afternoon (Time: 1 hour 30 minutes) Paper
reference WCH11/01
January 2026
Chemistry
International Advanced Subsidiary/Advanced Level
UNIT 1: Structure, Bonding and Introduction to
Organic Chemistry
You must have: Total Marks
Scientific calculator Pearson Edexcel International Advanced Subsidiary Level
in Chemistry
Instructions Paper 01: Structure, Bonding and Introduction to Organic
•• Use black ink or ball-point pen. Chemistry
If pencil is used for diagrams/sketches/graphs it must be dark (HB or B). WCH11/01
• Fill in the boxes at the top of this page with your name,
centre number and candidate number.
•• Answer allthequestions.
Answer
questions in the spaces provided
– there may be more space than you need.
Information
•• The total mark for this paper is 80.
The marks for each question are shown in brackets
– use this as a guide as to how much time to spend on each question.
• You will be assessed on your ability to organise and present information, ideas,
descriptions and arguments clearly and logically, including your use of grammar,
punctuation and spelling.
• A Periodic Table is printed on the back cover of this paper.
Advice
• Read each question carefully before you start to answer it.
•• Show all your working in calculations and include units where appropriate.
Try to answer every question.
• Check your answers if you have time at the end. Turn over
P79049APearson Education Ltd.
C:1/1/1/
*P79049A0124*
, SECTION A
Edexcel and BTEC Qualifications
Answer ALL the questions in this section.
DO NOT WRITE IN THIS AREA DO NOT WRITE IN THIS AREA DO NOT WRITE IN THIS AREA
DO NOT WRITE IN THIS AREA DO NOT WRITE IN THIS AREA DO NOT WRITE IN THIS AREA
You should aim to spend no more than 20 minutes on this section. Edexcel and BTEC qualifications are awarded by Pearson, the UK’s
largest awarding body. We provide a wide range of qualifications
For each question, select one answer from A to D and put a cross in the box . If you change including academic, vocational, occupational and specific
your mind, put a line through the box and then mark your new answer with a cross . programmes for employe a
qualifications websites at or .
1 Which property determines the order of elements in the Periodic Table? Alternatively, you c
contact us page at
A first ionisation energy
B relative atomic mass
C number of electrons in the outer shell
D number of protons in the nucleus Pearson: helping people progress, everywhere
(Total for Question 1 = 1 mark)
Pearson aspires to be the world’s leading learning company. Our aim is to
help everyone progress in their lives through education. We believe in every
2 Which atom has the most orbitals that contain a single electron?
kind of learning, for all kinds of people, wherever they are in the world. We’ve
A C been involved in education for over 150 years, and by working across 70
countries, in 100 languages, we have built an international reputation for our
B Cr
commitment to high standards and raising achievement through innovation
C Mn in education. Find out more about how we can help you and your students at:
D N
(Total for Question 2 = 1 mark)
3 The electronic configuration of element X is 1s2 2s2 2p6 3s2 3p4.
What is the formula of the compound formed when X reacts with potassium?
A KX
B K2X
C K3X
D KX2
January 2026
(Total for Question 3 = 1 mark) Question Paper Log Number P79049A
Publication Code WCH11_01_2601_MS
Use this space for any rough working. Anything you write in this space will gain no credit. All the material in this publication is
Pearson Education Ltd
2
*P79049A0224*
, General Marking Guidance
4 Which ion is not isoelectronic with the other ions?
• All candidates must receive the same treatment. Examiners must mark the
A Ti3+
DO NOT WRITE IN THIS AREA DO NOT WRITE IN THIS AREA DO NOT WRITE IN THIS AREA
DO NOT WRITE IN THIS AREA DO NOT WRITE IN THIS AREA DO NOT WRITE IN THIS AREA
first candidate in exactly the same way as they mark the last.
B Ca2+
• Mark schemes should be applied positively. Candidates must be rewarded
C P3– for what they have shown they can do rather than penalised for omissions.
D Cl– • Examiners should mark according to the mark scheme not according to their
(Total for Question 4 = 1 mark) perception of where the grade boundaries may lie.
• There is no ceiling on achievement. All marks on the mark scheme should be
5 Which properties of a cation result in the greatest polarising power? used appropriately.
• All the marks on the mark scheme are designed to be awarded. Examiners
Radius Charge should always award full marks if deserved, i.e. if the answer matches the
A small small mark scheme. Examiners should also be prepared to award zero marks if the
candidate’s response is not worthy of credit according to the mark scheme.
B large large
• Where some judgement is required, mark schemes will provide the principles
C small large
by which marks will be awarded and exemplification may be limited.
D large small • When examiners are in doubt regarding the application of the mark scheme
(Total for Question 5 = 1 mark) to a candidate’s response, the team leader must be consulted.
• Crossed out work should be marked UNLESS the candidate has replaced it
6 The first five ionisation energies of element Z are shown. with an alternative response.
1st 2nd 3rd 4th 5th
13 629
What is the formula of the most stable chloride of Z?
A ZCl4
B ZCl3
C ZCl2
D ZCl
(Total for Question 6 = 1 mark)
7 Which is not a neutralisation reaction?
A Zn + H2SO4 → ZnSO4 + H2
B CuO + 2HCl → CuCl2 + H2O
C NH3 + HNO3 → NH4NO3
D CaCO3 + 2CH3COOH → Ca(CH3COO)2 + H2O + CO2
(Total for Question 7 = 1 mark)
3
*P79049A0324* Turn over
, Using the Mark Scheme
8 A hydrocarbon contains 82.8% carbon by mass.
Examiners should look for qualities to reward rather than faults to penalise. This does
Which could be the molecular formula of the hydrocarbon?
NOT mean giving credit for incorrect or inadequate answers, but it does mean
DO NOT WRITE IN THIS AREA DO NOT WRITE IN THIS AREA DO NOT WRITE IN THIS AREA
DO NOT WRITE IN THIS AREA DO NOT WRITE IN THIS AREA DO NOT WRITE IN THIS AREA
A CH3 allowing candidates to be rewarded for answers showing correct application of
principles and knowledge. Examiners should therefore read carefully and consider
B C2H6 every response: even if it is not what is expected it may be worthy of credit.
C C2H5
The mark scheme gives examiners:
D C4H10 • an idea of the types of response expected
• how individual marks are to be awarded
(Total for Question 8 = 1 mark)
• the total mark for each question
• examples of responses that should NOT receive credit.
9 What is the percentage composition by mass of nitrogen in (NH4)2SO4 ?
/ means that the responses are alternatives and either answer should receive full
A 27.3%
credit.
B 21.2% ( ) means that a phrase/word is not essential for the award of the mark, but helps the
examiner to get the sense of the expected answer.
C 13.6%
D 10.6% Phrases/words in bold indicate that the meaning of the phrase or the actual word is
essential to the answer.
(Total for Question 9 = 1 mark) ecf/TE/cq (error carried forward) means that a wrong answer given in an earlier part of
a question is used correctly in answer to a later part of the same question.
10 What is the total number of ions in 10.0 g of iron(III) sulfate, Fe2(SO4)3 ?
Candidates must make their meaning clear to the examiner to gain the mark. Make
[Data: Molar mass of iron(III) sulfate = 399.9 g mol–1 sure that the answer makes sense. Do not give credit for correct words/phrases which
Avogadro constant (L) = 6.02 × 1023 mol–1] are put together in a meaningless manner. Answers must be in the correct context.
A 1.5 × 1022
Quality of Written Communication
B 3.0 × 1022
C 4.5 × 1022 Questions which involve the writing of continuous prose will expect candidates to:
• write legibly, with accurate use of spelling, grammar and punctuation in order to
D 7.5 × 1022 make the meaning clear
• select and use a form and style of writing appropriate to purpose and to complex
(Total for Question 10 = 1 mark)
subject matter
• organise information clearly and coherently, using specialist vocabulary when
11 What mass of barium chloride, BaCl2 , is needed to make 500 cm3 of a appropriate.
0.100 mol dm–3 solution?
[Data: Ar Ba = 137.3 Cl = 35.5] Full marks will be awarded if the candidate has demonstrated the above abilities.
Questions where QWC is likely to be particularly important are indicated (QWC) in the
A 41.66 g mark scheme, but this does not preclude others.
B 20.83 g
C 10.42 g
D 8.64 g
(Total for Question 11 = 1 mark)
4
*P79049A0424*
