IB Diploma Chemistry SL and HL: papers, Structure and Reactivity, the IA

IB Chemistry assessment

The weightings are the same at SL and HL. These details come from the IB's Chemistry subject brief for first assessment in 2025. The course also includes practical work and a collaborative sciences project.

SL or HL?

The IB recommends 150 teaching hours for SL and 240 for HL, of which 110 and 180 hours are syllabus content. HL goes deeper in every topic, and Reactivity 1.4, entropy and spontaneity, is additional higher level material.

IB Chemistry topics: Structure and Reactivity

IB Chemistry exam dates 2027

The IB's May 2026 schedule says the May 2027 exams will run from Friday 23 April to Wednesday 19 May 2027, with no exams on 1 May, subject to confirmation. Your IB coordinator has the subject-by-subject timetable for your zone.

IB grades and points

Each subject is graded from 1 to 7. Six subjects at up to 7 points each, plus up to 3 points from theory of knowledge and the extended essay, make a maximum of 45. The IB says the diploma needs at least 24 points and that other conditions must also be met. Grade boundaries are set for each subject after every session, so a raw mark from one year doesn't map exactly onto the next. Our IB mocks guide explains how points add up and how predicted grades work.

Worked examples

Structure 1.4: amount of substance

2.50 g of calcium carbonate (M = 100.09 g mol⁻¹) is 2.50 ÷ 100.09 = 0.0250 mol.

Structure 1.5: the ideal gas equation

The volume of 0.0250 mol of an ideal gas at 298 K and 100 kPa is:

That is 619 cm³. Keep pressure in Pa and volume in m³ for this equation.

Reactivity 1.2: enthalpy change from bond enthalpies

For CH₄ + 2O₂ → CO₂ + 2H₂O, using average bond enthalpies of C-H 414, O=O 498, C=O 804 and O-H 463 kJ mol⁻¹: bonds broken = 4 × 414 + 2 × 498 = 2652 kJ, bonds formed = 2 × 804 + 4 × 463 = 3460 kJ, so ΔH = 2652 − 3460 = −808 kJ mol⁻¹.

Reactivity 3.1: pH

A strong acid solution with [H⁺] = 1.0 × 10⁻³ mol dm⁻³ has pH = −log(1.0 × 10⁻³) = 3.00.

Practise bond enthalpy calculations in our Chemical Bonding course, then press Mark to check your answer in the course:

Use the daily paper as a short timed mock

Uni-Sine publishes a free daily paper for IB Chemistry SL and IB Chemistry HL. Each is a short timed mock: 8 questions worth 25 to 35 marks, with a suggested 35 to 45 minutes, marked when you finish. It is not a full IB paper, and the questions are original, not past papers.

• What it covers well: amount of substance, electron configuration, bonding and shapes, intermolecular forces, periodicity, enthalpy changes and Hess's law, entropy, kinetics and rate equations, equilibria, acids, bases and buffers, redox and electrode potentials, organic chemistry and spectroscopy.
• What it does not cover: the data-based and experimental questions of Paper 1B and the scientific investigation. The papers are organised by topic rather than the IB's Structure and Reactivity framework, so check any unfamiliar question against your syllabus.

For full papers under exam conditions, use IB past papers from your teacher, and read our IB mocks guide for how mocks feed your predicted grades.

Common mistakes in IB Chemistry

• Wrong units in pV = nRT. Use Pa, m³ and K.
• Bonds broken minus bonds made, the wrong way round. ΔH = energy to break − energy released forming.
• Dropping significant figures in data questions. Match the precision of the data.
• Vague mechanisms. Curly arrows must start from a lone pair or a bond and end at an atom or bond.

Read next

International · IBIB Physics SL and HL: Papers, Topics and 2027 ExamsIB Physics SL and HL explained: Paper 1A and 1B, Paper 2, the scientific investigation, topics A to E, HL-only content, May 2027 dates and worked examples.