IB Diploma Chemistry MCQs with answers
Practise IB Diploma Chemistry (SL / HL) with 203 exam-style MCQs, each with the answer and a short explanation. Every test is marked the moment you finish and shows your score chapter by chapter, so you know what to revise next. It is free and needs no sign-up.
203 questions · 6 chapters
What each chapter covers 6 chapters
The questions follow the syllabus chapter by chapter. You can test the whole subject or one chapter at a time.
- Structure 1: Models of the particulate nature of matter 45 questionsS1.1 Introduction to the particulate nature of matter, S1.2 The nuclear atom, S1.3 Electron configurations, S1.4 Counting particles by mass: the mole, S1.5 Ideal gases
- Structure 2: Models of bonding and structure 37 questionsS2.1 The ionic model, S2.2 The covalent model, S2.3 The metallic model, S2.4 From models to materials
- Structure 3: Classification of matter 22 questionsS3.1 The periodic table: classification of elements, S3.2 Functional groups: classification of organic compounds
- Reactivity 1: What drives chemical reactions? 27 questionsR1.1 Measuring enthalpy changes, R1.2 Energy cycles in reactions, R1.3 Energy from fuels
- Reactivity 2: How much, how fast and how far? 30 questionsR2.1 How much? The amount of chemical change, R2.2 How fast? The rate of chemical change, R2.3 How far? The extent of chemical change
- Reactivity 3: What are the mechanisms of chemical change? 42 questionsR3.1 Proton transfer reactions, R3.2 Electron transfer reactions, R3.3 Electron sharing reactions, R3.4 Electron-pair sharing reactions
Sample IB Diploma Chemistry MCQs with answers 12 questions
12 questions from the test, one or two from each chapter. Try each one, then open the answer.
1. Which technique is best for separating ethanol (boiling point 78 °C) from water (boiling point 100 °C)?
- A
paper chromatography
- B
filtration
- C
crystallization
- D
fractional distillation
Show answer
Answer: D. Ethanol and water are miscible liquids with different boiling points, so fractional distillation separates them; ethanol distils off first. Filtration only removes an insoluble solid from a liquid.
2. What is the monomer of poly(propene)?
- A
CH3CH2CH3
- B
CH2=CH2
- C
CH2=CHCl
- D
CH2=CHCH3
Show answer
Answer: D. Addition polymers form from alkenes: propene, CH2=CHCH3, opens its C=C bond. Propane has no double bond, so it cannot polymerize.
3. Why do boiling points increase from methane to butane?
- A
longer molecules have more electrons and more surface contact, so London forces are stronger
- B
hydrogen bonding increases with chain length
- C
the C–H bonds become stronger
- D
the molecules become more polar
Show answer
Answer: A. Alkanes are non-polar; only London forces act between them, and these grow with the number of electrons and area of contact. Boiling does not break C–H bonds.
4. Why is carbon monoxide from incomplete combustion dangerous?
- A
it binds to haemoglobin, reducing the ability of the blood to carry oxygen
- B
it is the main cause of acid rain
- C
it absorbs ultraviolet radiation in the stratosphere
- D
it dissolves in the lungs to form carbonic acid
Show answer
Answer: A. CO binds strongly to haemoglobin in place of oxygen, so less oxygen reaches the tissues. It is colourless and odourless, so it is hard to detect.
5. A reaction has Kc = 1 × 10−10 at 298 K. What does this tell us?
- A
the equilibrium lies far to the right, so products predominate
- B
the reaction is very slow at 298 K
- C
the equilibrium lies far to the left, so reactants predominate
- D
reactants and products are present in roughly equal amounts
Show answer
Answer: C. A very small K means the denominator (reactants) is much larger than the numerator (products) at equilibrium. K says nothing about rate.
6. What is a radical?
- A
a species with an unpaired electron
- B
a positively charged ion
- C
a species with a lone pair that it can donate
- D
an atom with a full outer shell
Show answer
Answer: A. A radical has an unpaired electron (shown as a dot), which makes it very reactive.
7. At the same temperature and pressure, which gas sample contains the same number of molecules as 2.0 dm3 of oxygen, O2?
- A
1.3 dm3 of ozone, O3, because each molecule has more atoms
- B
4.0 dm3 of helium, because helium is monatomic
- C
2.0 g of hydrogen gas
- D
2.0 dm3 of carbon dioxide
Show answer
Answer: D. Avogadro's law: equal volumes of gases at the same temperature and pressure contain equal numbers of molecules, whatever the gas.
8. Which statement about diamond and graphite is correct?
- A
diamond conducts electricity because each carbon atom has a free electron
- B
graphite conducts electricity because each carbon atom forms three covalent bonds, leaving one electron delocalized
- C
graphite is harder than diamond because its layers are tightly packed
- D
diamond is slippery because weak forces hold its layers together
Show answer
Answer: B. In graphite each C bonds to three others in layers, with one delocalized electron per atom. In diamond all four electrons are in bonds, so it does not conduct and has no layers.
9. Which statement about a homologous series is correct?
- A
all members have the same boiling point
- B
all members are structural isomers of each other
- C
members share a general formula and successive members differ by CH2
- D
members have different functional groups
Show answer
Answer: C. A homologous series has the same functional group and general formula, similar chemistry, and a gradual trend in physical properties. Isomers have the same molecular formula, which homologues do not.
10. Which statement expresses Hess's law?
- A
the enthalpy change is larger for a route with more steps
- B
the enthalpy change depends on the activation energy of each step
- C
the enthalpy change for a reaction is the same whichever route is taken from the same reactants to the same products
- D
the enthalpy change is zero for any reaction at 298 K
Show answer
Answer: C. Enthalpy is a state function: ΔH depends only on the initial and final states, not the pathway. This lets us combine equations to find unknown ΔH values.
11. According to collision theory, why do not all collisions between reactant particles lead to a reaction?
- A
collisions only react if a catalyst is present
- B
the colliding particles must have energy at least equal to the activation energy and a suitable orientation
- C
only collisions between particles with the same kinetic energy react
- D
the particles must have total energy equal to ΔH
Show answer
Answer: B. A successful collision needs enough energy to reach the transition state (E ≥ Ea) and the right geometry so the reacting atoms meet.
12. Which change is a reduction?
- A
Fe2+ → Fe3+
- B
Cl− → Cl2
- C
MnO4− → Mn2+
- D
SO2 → SO42−
Show answer
Answer: C. Mn goes from +7 to +2: a decrease in oxidation state is reduction. The other three are increases (+2 to +3, −1 to 0, +4 to +6).
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The 203 MCQs are our own, written to the syllabus in the style of the exam.
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