Cambridge IAS-Level · Analysis & Prediction

2023 Cambridge IAS-Level Chemistry (9701) Past Paper Analysis

This comprehensive analysis of the Cambridge International AS Level Chemistry series (October/November 2023, papers 13, 23, and 33) provides a detailed overview of student performance across multiple-choice, theoretical structured, and practical skills questions. Key focus areas include Period 3 periodicity, calorimetry calculations, organic reaction mechanisms, and qualitative inorganic chemical analysis.

Updated: 12 Jun 2026

Analysis Sample paper

Difficulty 3.5/5

Total marks

140

Duration

270 mins

Most tested

Reacting masses and volumes (of solutions and gases)

Paper breakdown

Paper 13 (Multiple Choice): 40 marks · 75 minsPaper 23 (AS Level Structured): 60 marks · 75 minsPaper 33 (Advanced Practical Skills): 40 marks · 120 mins

Top chapters

Reacting masses and volumes (of solutions and gases) · 15 marksAlkenes (Hydrocarbons) · 13 marksHess’s law · 12 marksIonisation energy · 8 marks

Exam Difficulty Verdict & Overview

The October/November 2023 series for AS Level Chemistry (comprising Papers 13, 23, and 33) presented a medium-to-hard challenge for candidates. While Paper 13 offered a standard spread of multiple-choice questions, Paper 23 featured demanding structured questions on Period 3 trends, Group 2 carbonates, and complex multi-step organic mechanisms. Paper 33 tested practical dexterity and analytical precision, focusing heavily on experimental design, Hess's Law calculations, and thorough observations in qualitative analysis.

Where the Marks Are Won and Lost

A significant portion of the marks in Paper 23 was concentrated in organic chemistry mechanisms (specifically alkene addition mechanisms and carbocation stability) and Period 3 physical trends (such as explaining the anomalies in first ionisation energy). In Paper 33, quantitative marks were heavily weighted towards the titration of potassium manganate(VII) and enthalpy changes of Group 2 oxides/hydroxides. Candidates who secured high marks demonstrated strong command over:

Constructing balanced equations with precise state symbols, especially for ionisation energies (e.g., \( \text{P(g)} \rightarrow \text{P}^+\text{(g)} + \text{e}^- \)).
Drawing accurate curly arrows in organic mechanisms, beginning exactly at electron pairs or bonds and terminating precisely at the target atoms.
Calculating gas volumes using the ideal gas equation \( pV = nRT \) with consistent unit conversions (e.g., converting \( \text{kPa} \) to \( \text{Pa} \) and volumes to \( \text{m}^3 \)).

Common Examiner Pitfalls

The principal examiner report highlights several recurring traps where even high-performing students lost easy marks:

Incorrect Rounding & Significant Figures: Many candidates rounded mid-step calculations prematurely, leading to inaccurate final answers. Answers to calculations should consistently be given to 3 significant figures.
Vague Definitions: Defining enthalpy change of formation without specifying 'from its constituent elements in their standard states' was a widespread error.
Qualitative Ambiguity: In practical observations, describing a positive carbon dioxide test as 'going milky' is no longer accepted; candidates must use the term 'white precipitate'. Additionally, confusing 'soluble precipitate' (a contradiction) with 'precipitate dissolving in excess' cost valuable marks.
Spin-Pair Repion Explanation: When explaining why sulfur has a lower first ionisation energy than phosphorus, many failed to specify that the paired electrons reside in the *same* \( \text{3p} \) orbital, experiencing mutual repulsion.

Preparation & Revision Strategy

To excel in future sessions, students should focus on active recall of core definitions and rigorous practice of mathematical chemistry:

Master Energy Cycles: Practice drawing complete Born-Haber and Hess's Law cycles, paying close attention to stoichiometry and arrows.
Inorganic Trends: Memorise the solubility and thermal stability trends of Group 2 hydroxides and carbonates, and be ready to explain them via cationic radius and polarisation.
Organic Synthesis Mapping: Build flowchart maps connecting alkenes, halogenoalkanes, alcohols, and carboxylic acids, noting precise reagents (e.g., *hot acidified concentrated* \( \text{KMnO}_4 \) vs *dilute* reagents).

Charts

Marks by chapter

See where the marks were concentrated so revision time goes to the highest-value topics.

Question type mix

Compare the mark share of each paper section and question type.

Multiple Choice40 marks · 40 questions
Structured60 marks · 4 questions
Practical40 marks · 3 questions

Mark accessibility

Estimate which marks were basic, mid-level, or high-difficulty.

71%within easy or medium reach

easy: 35 marksmedium: 65 markshard: 40 marks

Difficulty trend

Compare difficulty across recent years.

Command word frequency

Spot common command words so answers match the expected response style.

Skill weighting

Shows the skill mix this paper tested most heavily.

Study ROI

Bigger bubbles recur more often; higher bubbles carry more marks, helping you rank revision priorities.

Reacting masses and volumes (Atoms, molecules and stoichiometry)

15 marks · Difficulty 2 · recurrence 5%

Alkenes (Hydrocarbons) - mechanisms and carbocation stability

13 marks · Difficulty 3.5 · recurrence 5%

Hess's Law and Calorimetry Calculations

12 marks · Difficulty 3 · recurrence 4%

Ionisation Energy Period 3 Trends

8 marks · Difficulty 3 · recurrence 4%

Time vs marks

Compare marks with suggested time allocation to plan exam pacing.

marksmins

Next-year prediction

Topics worth watching next year, with the reason shown directly below each bar.

Halogenoalkanes and Nucleophilic Substitution85%

Nucleophilic substitution mechanisms (SN1 vs SN2) are highly recurring, but were tested primarily in multiple-choice questions this series, making them overdue for a prominent structured question.

Chemical Periodicity of Period 3 Oxides80%

Acid-base properties and reactions of Period 3 oxides (e.g. Na2O, Al2O3, SO2, SO3) with water were lightly touched upon in Paper 13, and are highly likely to reappear as major balanced equation questions in Paper 2.

Infrared Spectroscopy and Mass Spectrometry Integration75%

Usually paired with organic analysis questions to determine unknown compounds, this topic is a stable expectation in Paper 2.

Topic-year heatmap

Compare topic weight by year to spot recurring and returning areas.

Jun 2023 (V1)

Jun 2023 (V2)

Jun 2023 (V3)

Nov 2023 (V1)

Nov 2023 (V2)

Nov 2023 (V3)

Atomic structure (Physical chemistry (AS Level))

Electrons, energy levels and atomic orbitals

Ionisation energy

Particles in the atom and atomic radius

Atoms, molecules and stoichiometry (Physical chemistry (AS Level))

Relative masses of atoms and molecules

Reacting masses and volumes

The gaseous state: ideal and real gases and pV = nRT

Formulas

Shapes of molecules

Examiner insights

Official report

Common pitfalls

Omitting state symbols in equations representing first ionisation energy.
Omitting the brackets surrounding side-chain methyl groups when drawing structural formulae.
Premature rounding of intermediate steps in multi-stage calculations, resulting in inaccurate final answers.
Failing to state 'from its constituent elements in their standard states' when defining standard enthalpy change of formation.
Using non-volumetric apparatus like measuring cylinders instead of a volumetric pipette or burette to prepare standard solutions.
Failing to double the single reading uncertainty when calculating the percentage error for a thermometer measurement (which requires two readings).

Misconceptions

Believing that ethanoic acid's partial dissociation means it produces fewer water molecules during neutralisation, making it less exothermic, rather than understanding that energy is absorbed to complete the dissociation of the weak acid.
Thinking that the addition of an inert gas at constant volume shifts the dynamic equilibrium position or alters the reaction rate.
Assuming that the ethyl group in ethoxide ions delocalises the negative charge, rather than concentrating it due to the positive inductive effect, which makes ethoxide a stronger base than hydroxide.
Confusing the reagents needed to convert halogenoalkanes to nitriles (ethanolic KCN) with those needed for ethanal to hydroxynitriles (HCN + CN- catalyst).

Where marks are lost

Losing marks on organic mechanism diagrams by not starting curly arrows precisely at lone pairs or double bonds, or pointing them to incorrect destinations.
Failing to multiply the moles of glucose by 12 to find the total moles of CO2 and H2O produced in the stoichiometric calculation.
Describing positive carbon dioxide tests as 'goes milky' or 'cloudy' instead of the required terminology 'white precipitate'.
Using the mass of solid reactant rather than the mass of the solution (water) in the calorimetry equation q = mcΔT.
Omitting the negative sign from calculated exothermic enthalpy changes.

Estimated grade cut-off

Updated: 12 Jun 2026

Source: Cambridge International component thresholds (AS aggregate, derived)

Level	Mark	Percentage
A	91/140	65%
B	74/140	53%
C	63/140	45%
D	52/140	37%
E	42/140	30%

Estimated cut-offs from Cambridge International component thresholds (AS aggregate, derived); may differ from the official boundaries.

Know what the examiners want — now go get those marks

Thinka is an AI practice app used by 100,000+ DSE students to drill questions and get instant feedback on every answer. You already know the high-frequency topics and where marks are lost — now practice those specifically on Thinka and turn this analysis into actual marks.

Start Practising Free See pricing

Know what's tested? Drill those topics on Thinka — AI questions, instant marking.

Start Practising Free