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O Level / IGCSE Chemistry MCQs with answers

Practise O Level / IGCSE Chemistry (5070 / 0620) with 438 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.

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O Level / IGCSE Chemistry MCQs with answers

Practise O Level / IGCSE Chemistry (5070 / 0620) with 438 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.

438 questions · 12 chapters · 14 Cambridge past papers · 5 mock exams

What each chapter covers 12 chapters

The questions follow the syllabus chapter by chapter. You can test the whole subject or one chapter at a time.

  1. States of matter 18 questionsSolids, liquids and gases, Diffusion
  2. Atoms, elements and compounds 61 questionsElements, compounds and mixtures, Atomic structure and the Periodic Table, Isotopes, Ion and ionic bonds, Simple molecules and covalent bonds, Giant covalent structures, Metallic bonding
  3. Stoichiometry 30 questionsFormulae, Relative masses of atoms and molecules, The mole and the Avogadro constant
  4. Electrochemistry 13 questionsElectrolysis
  5. Chemical energetics 10 questionsExothermic and endothermic reactions
  6. Chemical reactions 43 questionsPhysical and chemical changes, Rate of reaction, Reversible reactions and equilibrium, Redox
  7. Acids, bases and salts 26 questionsThe characteristic properties of acids and bases, Oxides, Preparation of salts
  8. The Periodic Table 43 questionsArrangement of elements, Group I properties, Group VII properties, Transition elements, Noble gases
  9. Metals 53 questionsProperties of metals, Uses of metals, Alloys and their properties, Reactivity series, Corrosion of metals, Extraction of metals
  10. Chemistry of the environment 28 questionsWater, Fertilisers, Air quality and climate
  11. Organic chemistry 77 questionsFormulae, functional groups and terminology, Naming organic compounds, Fuels, Alkanes, Alkenes, Alcohols, Carboxylic acids, Polymers
  12. Experimental techniques and chemical analysis 36 questionsExperimental design, Chromatography, Separation and purification, Identification of ions and gases
Sample O Level / IGCSE 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. A beaker of water is left in a warm room and slowly evaporates. Why does the water that remains become slightly cooler?

  1. A
    evaporation only happens at the boiling point, so the cooling must come from the room
  2. B
    the remaining particles become heavier and slower as they clump together
  3. C
    particles from the air enter the water and take energy from it as they dissolve
  4. D
    the fastest particles escape, so the average kinetic energy of the particles left falls
Show answer

Answer: D. Only the fastest particles at the surface have enough energy to escape. Losing them lowers the average kinetic energy, and so the temperature, of the liquid left behind.

2. Which statement about a compound is correct?

  1. A
    it contains only one type of atom
  2. B
    it can be separated into its elements by filtration
  3. C
    its elements are chemically bonded in a fixed ratio
  4. D
    its properties are the same as those of its elements
Show answer

Answer: C. A compound has two or more elements chemically combined in a fixed ratio, with properties different from its elements. A mixture can be separated physically.

3. Solid calcium carbonate reacts with dilute hydrochloric acid. Which equation, including state symbols, is correct?

  1. A
    CaCO3(aq) + 2HCl(aq) → CaCl2(s) + H2O(l) + CO2(g)
  2. B
    CaCO3(s) + 2HCl(aq) → CaCl2(aq) + H2O(l) + CO2(g)
  3. C
    CaCO3(s) + HCl(aq) → CaCl(aq) + H2O(l) + CO2(g)
  4. D
    CaCO3(s) + 2HCl(aq) → CaCl2(aq) + H2(g) + CO2(g)
Show answer

Answer: B. Calcium carbonate is an insoluble solid and calcium chloride is soluble. Calcium ions are Ca2+, so two HCl are needed; a carbonate gives water and carbon dioxide, not hydrogen.

4. Dilute sulfuric acid is electrolysed with inert electrodes. What is the ratio of the volume of gas at the cathode to the volume at the anode?

  1. A
    1 : 1
  2. B
    1 : 2
  3. C
    2 : 1
  4. D
    4 : 1
Show answer

Answer: C. Hydrogen at the cathode (4H+ + 4e− → 2H2) and oxygen at the anode (4OH− → O2 + 2H2O + 4e−): two volumes of hydrogen for every one of oxygen.

5. Bond energies: H–H 436 kJ/mol, Cl–Cl 242 kJ/mol, H–Cl 431 kJ/mol. What is the energy change for H2 + Cl2 → 2HCl?

  1. A
    −184 kJ/mol
  2. B
    +184 kJ/mol
  3. C
    −247 kJ/mol
  4. D
    +678 kJ/mol
Show answer

Answer: A. Bonds broken: 436 + 242 = 678 kJ. Bonds made: 2 × 431 = 862 kJ. ΔH = 678 − 862 = −184 kJ/mol, exothermic.

6. In a burning candle, solid wax first melts and then the molten wax burns. Which statement is correct?

  1. A
    melting is a chemical change and burning is a physical change
  2. B
    both are chemical changes
  3. C
    both are physical changes
  4. D
    melting is a physical change and burning is a chemical change
Show answer

Answer: D. Molten wax is still wax, so melting is physical. Burning produces carbon dioxide and water, which are new substances.

7. Zinc oxide reacts with dilute hydrochloric acid and also with aqueous sodium hydroxide. What type of oxide is it?

  1. A
    neutral, because it does not react with acids
  2. B
    amphoteric, because it reacts with acids and alkalis
  3. C
    acidic, because it reacts with the alkali
  4. D
    basic, because it reacts with the acid
Show answer

Answer: B. An oxide that reacts with both acids and bases to form a salt and water is amphoteric. Aluminium oxide behaves the same way.

8. Which statement describes the change going down Group VII from chlorine to iodine?

  1. A
    density decreases and reactivity increases
  2. B
    density and reactivity both increase
  3. C
    density increases and reactivity decreases
  4. D
    the elements change from diatomic to monatomic
Show answer

Answer: C. The halogens become denser and less reactive down the group. All exist as diatomic molecules: Cl2, Br2, I2.

9. Magnesium is more reactive than copper. What does this mean in terms of ions?

  1. A
    magnesium atoms have more protons than copper atoms
  2. B
    magnesium atoms gain electrons more readily than copper atoms
  3. C
    magnesium atoms lose electrons more readily than copper atoms do
  4. D
    copper atoms form positive ions more readily than magnesium atoms
Show answer

Answer: C. Reactivity of metals is their tendency to form positive ions. That is why magnesium displaces Cu2+: Mg + Cu2+ → Mg2+ + Cu.

10. In water treatment, why is chlorine added?

  1. A
    to remove solid particles
  2. B
    to kill bacteria
  3. C
    to soften the water
  4. D
    to improve the taste
Show answer

Answer: B. Chlorination sterilises the water. Filtration removes solids; sedimentation settles larger particles.

11. Which statement about PET is correct?

  1. A
    it can be converted back into its monomers and re-polymerised
  2. B
    it is a polyamide, with amide linkages between the monomers
  3. C
    it is an addition polymer made from ethene
  4. D
    it can never be recycled, so it must be buried in landfill
Show answer

Answer: A. PET is a polyester. It can be broken down into its monomers, which are then used to make new PET.

12. Salt is to be obtained from a mixture of salt and sand. Which sequence of steps is correct?

  1. A
    distil the dry mixture and collect the salt in the condenser
  2. B
    filter the dry mixture and collect the salt from the filtrate
  3. C
    add water, stir, filter, then evaporate the filtrate to crystallise
  4. D
    add water, evaporate, then filter off the salt
Show answer

Answer: C. Salt dissolves but sand does not. Filtering removes the sand; the salt is then recovered from the filtrate.

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Ways to practise 7 ways

When you get a question wrong, a short note called "The idea behind this" explains the topic it belongs to, with the rules to remember and a worked example.

Common questions

Is this O Level / IGCSE Chemistry test free?

Yes. Every test and every explanation is free, and you do not need an account. If you sign in, your results are kept across your devices.

Are these past paper questions?

The 438 MCQs are our own, written to the syllabus in the style of the exam. The 14 Cambridge past papers are listed separately inside the test.

How is the test marked?

Instantly. You get your score, the right answer and an explanation for every question, and a list of the topics to work on.

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