JAMB Chemistry past questions and answers

Checked by the Skolra question team · Last updated 23 October 2026

JAMB Chemistry: 575 past questions from 10 papers between 2015 and 2025, each with the answer and an explanation. In the UTME you answer 40 Chemistry questions, with Use of English and two other subjects, in 2 hours. Here are ten.

1. 1.

   The most suitable indicator to be used when reacting ethanedioic acid with potassium hydroxide is 

   1. A
      Phenolphthalein
      Correct
   2. B
      Methyl orange
   3. C
      Methyl red
   4. D
      Litmus solution
   Show answerHide answer

   Answer: A

   Ethanedioic acid (oxalic acid) is a weak acid, while potassium hydroxide is a strong base. When a weak acid reacts completely with a strong base, the salt formed (potassium ethanedioate) hydrolyses in water and the resulting solution is alkaline at the equivalence point (pH above 7), not neutral.

2. 2.

   Which of the following pollutants will lead to the depletion of ozone layer?

   1. A
      Chlorofluorocarbon
      Correct
   2. B
      Hydrogen sulphide
   3. C
      Carbon(IV) oxide
   4. D
      Sulphur(IV) oxide
   Show answerHide answer

   Answer: A

   Chlorofluorocarbon (CFC) is the pollutant responsible for depletion of the ozone layer.

   CFCs were once common in refrigerators, air conditioners and aerosol sprays. When they drift up into the stratosphere, ultraviolet radiation breaks them apart and releases chlorine free radicals. Each chlorine radical reacts with ozone (O3) to form oxygen (O2) and chlorine monoxide, and the chlorine is regenerated to attack more ozone molecules — so a single CFC molecule can destroy thousands of ozone molecules over time. This thins the ozone layer, allowing more harmful UV radiation to reach the earth's surface.

3. 3.

   The radio isotope used in industrial radiography for the rapid checking of faults in welds and casting is?

   1. A
      Carbon-14
   2. B
      Uranium-235
   3. C
      Cobalt-60
      Correct
   4. D
      Iodine-131
   Show answerHide answer

   Answer: C

   Cobalt-60 emits strong, penetrating gamma rays that can pass through thick metal welds and castings, exposing a photographic film on the far side. Flaws inside the metal show up as differences in the exposed image, making Co-60 the standard source for industrial radiography.

   Uranium-235 is used as a nuclear reactor fuel, not for radiography. Carbon-14 is used for dating organic archaeological material because of its long, slow decay, not for penetrating metal. Iodine-131 is a medical isotope used in treating and imaging the thyroid gland.

4. 4.

   The sulphide that is commonly used in coating electric fluorescent tubes is?

   1. A
      Cadmium sulphide
   2. B
      Copper(II) sulphide
   3. C
      Lead(II) sulphide
   4. D
      Zinc sulphide
      Correct
   Show answerHide answer

   Answer: D

   Zinc sulphide is the compound commonly used to coat the inside of electric fluorescent tubes.

   Inside a fluorescent tube, electric current passing through mercury vapour produces ultraviolet (UV) light, which is invisible to the eye. The inner wall of the tube is coated with a phosphorescent/fluorescent substance, and zinc sulphide is one of the classic phosphor materials used for this purpose: it absorbs the UV radiation and re-emits it as visible light, which is why the tube glows brightly.

5. 5.The relative atomic mass of a naturally occurring lithium consisting of 90%$\frac{7}{3}$Li and 10%$\frac{6}{3}$Li is
   1. A
      6.1
   2. B
      6.5
   3. C
      7.0
   4. D
      6.9
      Correct
   Show answerHide answer

   Answer: D

   Relative atomic mass = (0.90 × 7) + (0.10 × 6) = 6.3 + 0.6 = 6.9.

   6.1 comes from swapping the two percentages the wrong way round. 7.0 is just the mass number of the more abundant isotope taken alone, ignoring the lighter isotope entirely. 6.5 is a plain, unweighted average of the two mass numbers, which ignores that the two isotopes are not equally abundant.

6. 6.

   If 1 litre of 2.2M sulphuric acid is poured into a bucket containing 10 litres of water and the resulting solution mixed thoroughly, the resulting sulphuric acid concentration will be

   1. A
      0.22M
   2. B
      2.00M
   3. C
      0.02M
   4. D
      0.20M
      Correct
   Show answerHide answer

   Answer: D

   Moles of acid = 2.2 × 1 = 2.2 mol. Total volume after mixing = 1 + 10 = 11 litres. New concentration = 2.2 ÷ 11 = 0.20M.

   0.02M would come from dividing by 110 litres instead of 11. 0.22M comes from ignoring the added water volume and dividing by only 10 litres. 2.00M does not correctly account for the dilution at all.

7. 7.

   The acid used in making baking soda and soft drink is

   1. A
      Acetic acid
   2. B
      Citric acid
   3. C
      Carbonic acid
      Correct
   4. D
      Hydrochloric acid
   Show answerHide answer

   Answer: C

   Carbonic acid (H₂CO₃) is the acid common to both baking soda and soft drinks.

   When carbon(IV) oxide gas dissolves in water, it forms carbonic acid: CO₂ + H₂O → H₂CO₃. This weak, unstable acid is what is used to carbonate soft drinks, giving them their fizz, and it is also the acid involved in producing sodium bicarbonate (baking soda), since CO₂ reacting in the presence of a sodium base gives NaHCO₃.

   Citric acid is found naturally in citrus fruits and is added as a flavouring/preservative in some drinks, but it is not the acid responsible for carbonation or for making baking soda.

8. 8.

   The gas that is commonly used to demonstrate the fountain experiment is

   1. A
      Sulphur(IV) oxide
   2. B
      Carbon(IV) oxide
   3. C
      Hydrogen chloride
   4. D
      Ammonia
      Correct
   Show answerHide answer

   Answer: D

   Correct answer: Ammonia.

   The fountain experiment shows that a gas is extremely soluble in water. A flask of the dry gas is connected by a jet tube to a trough of water, and a squeeze of the dropper starts water dissolving the gas inside the flask. As the gas dissolves, the pressure inside the flask falls far below atmospheric pressure, and the outside water is forced up the tube in a fountain.

9. 9.

   Identify the reducing agent in the following reaction:
   Zn + CuSO$_4$ ZnSO$_4$ + Cu

   1. A
      Copper(II) sulphate, CuSO₄
   2. B
      Zinc sulphate, ZnSO₄
   3. C
      Copper, Cu
   4. D
      Zinc, Zn
      Correct
   Show answerHide answer

   Answer: D

   Reducing agent = zinc, Zn.

   In the reaction Zn + CuSO₄ → ZnSO₄ + Cu, track the oxidation states: zinc starts as Zn (oxidation state 0) and ends up as Zn²⁺ in ZnSO₄. It has lost two electrons, so zinc is oxidized. A substance that is itself oxidized (loses electrons) is the one that reduces the other species — that makes it the reducing agent.

   Meanwhile, copper starts as Cu²⁺ in CuSO₄ (oxidation state +2) and ends up as Cu metal (oxidation state 0). It has gained two electrons, so copper(II) sulphate is reduced — it is the oxidizing agent, not the reducing agent, so copper(II) sulphate, CuSO₄ is a wrong choice for this question.

10. 10.

    The nucleusof a hydrogen atom consist of a?

    1. A
       a proton and a neutron
    2. B
       a proton and an electron
    3. C
       a single proton only
       Correct
    4. D
       a neutron only
    Show answerHide answer

    Answer: C

    Hydrogen has atomic number 1, meaning it has just 1 proton. The most common form of hydrogen (protium, which makes up about 99.98% of natural hydrogen) has no neutron in its nucleus at all.

    So the nucleus of a hydrogen atom consists of a single proton only — that is correct.

    The electron is not inside the nucleus; it moves around the nucleus in an orbital, so an option that puts a proton and an electron together in the nucleus is wrong — that mixes up nuclear particles with the orbiting electron.

    A proton and a neutron together describe the nucleus of deuterium (an isotope of hydrogen), not ordinary hydrogen, so that option is a common mix-up but not correct here.

The questions come from past JAMB, WAEC and NECO papers. We use software to help write the answer options and explanations, and every answer is checked twice before it goes on the site. How we check

Spotted a wrong answer? Tell us from the app or on the contact page and we check it.

Sit a full timed 40-question JAMB Chemistry test in the Skolra app

All 575 JAMB Chemistry questions we hold are in the app, each with the answer and an explanation. Practise by year, or sit a full JAMB mock exam.

Download for WindowsDownload for Mac

About the app · Skolra for Windows · Skolra for Mac