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MDCAT Chemistry MCQs with answers

Practise MDCAT Chemistry (PMDC 2025-26) with 820 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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MDCAT Chemistry MCQs with answers

Practise MDCAT Chemistry (PMDC 2025-26) with 820 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.

820 questions · 20 chapters

What each chapter covers 20 chapters

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

  1. Chemistry · Fundamental concepts of chemistry 34 questionsThe mole, Stoichiometry
  2. Chemistry · Atomic structure 40 questionsParticles, photons and the Bohr model, Orbitals and electronic configuration
  3. Chemistry · Gases 30 questionsGas laws, Kinetic theory and real gases
  4. Chemistry · Liquids 45 questionsIntermolecular forces, Properties of liquids
  5. Chemistry · Solids 37 questionsCrystalline solids
  6. Chemistry · Chemical equilibrium 49 questionsEquilibrium and Le Chatelier's principle, Ionic equilibria
  7. Chemistry · Reaction kinetics 39 questionsRate and rate law, Activation energy and catalysis
  8. Chemistry · Thermochemistry and energetics 32 questionsEnthalpy changes, First law and Hess's law
  9. Chemistry · Electrochemistry 29 questionsOxidation numbers and redox, Electrode potentials and cells
  10. Chemistry · Chemical bonding 51 questionsIonic and covalent bonding, Shapes of molecules
  11. Chemistry · s and p block elements 61 questionsPeriodic trends and the s block, The p block
  12. Chemistry · Transition elements 37 questionsProperties of transition elements, Complexes
  13. Chemistry · Fundamental principles of organic chemistry 39 questionsClassification and isomerism, Bonding and reactivity in carbon compounds
  14. Chemistry · Hydrocarbons 55 questionsAlkanes and alkenes, Alkynes and benzene
  15. Chemistry · Alkyl halides 30 questionsAlkyl halides
  16. Chemistry · Alcohols and phenols 63 questionsAlcohols, Phenols and ethers
  17. Chemistry · Aldehydes and ketones 40 questionsAldehydes and ketones
  18. Chemistry · Carboxylic acids 51 questionsCarboxylic acids and derivatives
  19. Chemistry · Macromolecules 48 questionsPolymers, Biological macromolecules
  20. Chemistry · Industrial chemistry 10 questionsIndustrial chemistry
Sample MDCAT 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. What mass of calcium carbonate, CaCO3, contains 4.8 g of oxygen? (C = 12, O = 16, Ca = 40)

  1. A
    10 g
  2. B
    30 g
  3. C
    15 g
  4. D
    5.0 g
Show answer

Answer: A. 4.8 ÷ 16 = 0.30 mol of O atoms, and each CaCO3 unit holds three O atoms, so 0.10 mol of CaCO3 = 0.10 × 100 = 10 g is needed. 30 g ignores the three O atoms per formula unit, and 15 g treats the oxygen as O2 (32 g mol−1).

2. Using 1/λ = RH(1/n12 − 1/n22), what is the ratio of the wavelength of the first (longest-wavelength) Lyman line to that of the first Balmer line of hydrogen?

  1. A
    5 : 27
  2. B
    27 : 5
  3. C
    1 : 4
  4. D
    4 : 1
Show answer

Answer: A. First Lyman line (n = 2 → 1): 1/λ = RH(1 − 1/4) = 3RH/4; first Balmer line (n = 3 → 2): 1/λ = RH(1/4 − 1/9) = 5RH/36. The wavelengths are the reciprocals, so λLyman : λBalmer = 4/3 : 36/5 = 5 : 27. 27 : 5 compares the wave numbers instead, and 1 : 4 is the ratio of the two series limits.

3. The average kinetic energy of the molecules of a gas is E at −73 °C. What is it at 327 °C?

  1. A
    3E
  2. B
    4.5E
  3. C
    √3 E
  4. D
    9E
Show answer

Answer: A. Average kinetic energy is proportional to the absolute temperature: −73 °C = 200 K and 327 °C = 600 K, so it becomes 3E. Dividing the Celsius values (327 ÷ 73) gives about 4.5E, and √3 is the factor for the root mean square speed, not the energy.

4. Water is boiling steadily in an open pan at 1 atm. If the flame is turned up, the temperature of the boiling water

  1. A
    rises steadily
  2. B
    stays at 100 °C
  3. C
    falls slightly
  4. D
    rises to a new fixed value above 100 °C
Show answer

Answer: B. Water boils when its vapour pressure equals the external pressure, 760 torr at 100 °C. Extra heat only supplies the heat of vaporisation faster, so the water boils away faster while its temperature stays at 100 °C.

5. Which of these is a general property of solids?

  1. A
    they take the shape of any container they are put in
  2. B
    their particles can diffuse, but far more slowly than in liquids
  3. C
    they are easily squeezed into a much smaller volume
  4. D
    they flow slowly whenever a small force is applied to them
Show answer

Answer: B. Solids are rigid, keep their shape and are almost incompressible because their particles are closely packed in fixed positions; even so, particles do diffuse very slowly, so two metal blocks clamped together for years show a little mixing at the join. Taking the shape of the container and flowing are properties of fluids.

6. The reaction A ⇌ B is started with pure A. By time t, [A] has fallen from 1.0 to 0.30 mol dm−3 and [B] has risen to 0.70 mol dm−3; after t, both stay constant. Which statement describes the system after time t?

  1. A
    no more A turns into B, as the reaction has stopped
  2. B
    the forward rate exceeds the reverse rate, since [B] > [A]
  3. C
    the system is not at equilibrium, since [A] ≠ [B]
  4. D
    A turns into B and B turns into A at equal rates
Show answer

Answer: D. Constant concentrations with both A and B present mean dynamic equilibrium: the forward and reverse reactions continue at equal rates. Equilibrium does not need equal concentrations; here Kc = 0.70 ÷ 0.30 ≈ 2.3.

7. The rate of a reaction in solution is usually expressed in

  1. A
    mol dm−3
  2. B
    s−1
  3. C
    dm3 mol−1 s−1
  4. D
    mol dm−3 s−1
Show answer

Answer: D. Rate = change in concentration ÷ time taken, so its unit is mol dm−3 s−1. mol dm−3 is a concentration, and s−1 is the unit of a first-order rate constant.

8. A gas in a cylinder is compressed: 40 kJ of work is done on it while it gives out 15 kJ of heat to the surroundings. Using ΔE = q + w, the change in its internal energy is

  1. A
    −25 kJ
  2. B
    +55 kJ
  3. C
    +25 kJ
  4. D
    −55 kJ
Show answer

Answer: C. Heat leaves the system, so q = −15 kJ; work is done on the system, so w = +40 kJ. ΔE = −15 + 40 = +25 kJ. Adding the two magnitudes gives +55 kJ, and reversing both signs gives −25 kJ.

9. A galvanic cell is made from a nickel electrode in 1 M Ni2+ (E° = −0.25 V) and a silver electrode in 1 M Ag+ (E° = +0.80 V). Its standard emf is

  1. A
    0.55 V
  2. B
    1.85 V
  3. C
    1.05 V
  4. D
    −1.05 V
Show answer

Answer: C. Silver has the higher E°, so it is the cathode: E°cell = 0.80 − (−0.25) = 1.05 V. E° values are not multiplied by the 2 in 2Ag+ (doing so gives 1.85 V), and 0.55 V ignores the negative sign of nickel.

10. The O–C–O angle in carbon dioxide is 180°, but the O–S–O angle in sulphur dioxide is about 119°. Why?

  1. A
    sulphur has a lone pair, so its three regions spread at about 120°
  2. B
    sulphur is larger than carbon, so its bonds bend further apart
  3. C
    sulphur is sp3 hybridised, so the angle is near 109.5°
  4. D
    the S=O bonds are polar, whereas the C=O bonds are non-polar
Show answer

Answer: A. Carbon in CO2 has two regions of electron density and no lone pair, so they lie opposite each other. Sulphur in SO2 has two bonding regions and one lone pair, three regions that repel to about 120°, so the molecule is bent. The C=O bonds are polar too; they cancel because CO2 is linear.

11. Which alkali metal hydroxide is the least soluble in water?

  1. A
    LiOH
  2. B
    NaOH
  3. C
    KOH
  4. D
    CsOH
Show answer

Answer: A. Solubility of the group 1 hydroxides increases down the group, so LiOH is the least soluble: the small Li+ and OH− ions form a lattice with a very high lattice energy.

12. Which ion has the most unpaired electrons, and so is the most strongly paramagnetic? (Z: Mn 25, Fe 26, Ni 28, Cu 29)

  1. A
    Fe2+
  2. B
    Ni2+
  3. C
    Mn2+
  4. D
    Cu2+
Show answer

Answer: C. Mn2+ is 3d5: one electron in each of the five d orbitals, all unpaired (Hund's rule). Fe2+ (3d6) has four, Ni2+ (3d8) two and Cu2+ (3d9) one.

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The 820 MCQs are our own, written to the syllabus in the style of the exam.

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