JAMB Chemistry 2022 past questions

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

Ten questions from the 2022 JAMB Chemistry paper, with answers and explanations. We hold 38 questions from this paper, and the Skolra app has all of them.

JAMB Chemistry 2022 questions and answers

1. 1.In which of the following will hydrogen form ionic compound?
   1. A
      Hydrogen chloride
   2. B
      Methane
   3. C
      Sodium hydride
      Correct
   4. D
      Ammonia
   Show answerHide answer

   Answer: C

   Sodium hydride (NaH) is the correct answer. Hydrogen forms an ionic (electrovalent) compound only when it reacts with a metal that is far more electropositive than itself, typically the alkali metals (Group 1) and some alkaline earth metals.

   So only the reaction with a strongly electropositive metal like sodium produces a true ionic hydride.

2. 2.

   Addition of charcoal to the filter bed of sand during water treatment for township supply is to?

   1. A
      To remove the larger suspended solid particles before the water reaches the sand layer
   2. B
      To adsorb impurities that cause unpleasant taste, odour and colour in the water
      Correct
   3. C
      To kill bacteria and other disease-causing microorganisms present in the water
   4. D
      To neutralise the acidity of the water and raise its pH before it is distributed
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   Answer: B

   Charcoal is added to the filter bed mainly to adsorb impurities that cause unpleasant taste, odour and colour in the water. Charcoal (particularly activated charcoal) is highly porous, giving it a very large surface area that traps dissolved organic substances, gases and colour-forming compounds as water passes through it.

   Killing bacteria and other microorganisms is not the role of charcoal — that is achieved by chlorination or other disinfection steps, not by adsorption.

   So among the treatment steps, charcoal's specific job is adsorbing the impurities responsible for bad taste, odour and colour.

3. 3.

   Crude petroleum is converted to useful products by the processof?

   1. A
      Polymerization
   2. B
      Fractional distillation
      Correct
   3. C
      Fermentation
   4. D
      Cracking
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   Answer: B

   Fractional distillation is the process by which crude petroleum is converted into useful products. Crude oil is a mixture of many hydrocarbons with different boiling points. When it is heated in a fractionating column, the different hydrocarbon fractions (like petrol, kerosene, diesel, and bitumen) vaporize and condense at different heights of the column according to their boiling points, allowing them to be separated into useful products.

4. 4.

   The pollutant usually presents in a city which generates its electricity from coal?

   1. A
      Sulphur(IV) oxide
      Correct
   2. B
      Carbon(II) oxide
   3. C
      Nitrogen(IV) oxide
   4. D
      Carbon(IV) oxide
   Show answerHide answer

   Answer: A

   Sulphur(IV) oxide (SO2) is the pollutant usually associated with a city that generates its electricity from coal.

   Coal is not pure carbon — it contains sulphur impurities, mainly as iron pyrites and organic sulphur compounds. When coal is burnt in power stations, this sulphur combines with oxygen to form sulphur(IV) oxide gas, which escapes into the atmosphere. This gas is a major cause of acid rain and respiratory problems in cities that depend heavily on coal for electricity.

5. 5.

   2H$_2$ + O$_2$ 2H$_2$O

   From the equationabove, calculate the volume of unreacted oxygen gas if a mixture of 50cm$^3$ of hydroden and 75cm$^3$ of oxygen are involved

   1. A
      75cm³
   2. B
      25cm³
   3. C
      50cm³
      Correct
   4. D
      100cm³
   Show answerHide answer

   Answer: C

   The equation 2H₂ + O₂ → 2H₂O shows that 2 volumes of hydrogen react with 1 volume of oxygen.

   So 50cm³ of hydrogen needs only half that volume of oxygen to react completely: 50 × ½ = 25cm³ of oxygen used up.

   Oxygen supplied was 75cm³, so the oxygen left unreacted = 75cm³ − 25cm³ = 50cm³.

   A candidate who stops at the oxygen actually consumed (25cm³) mistakes that figure for the leftover amount — it is the opposite. Picking the full 75cm³ wrongly assumes none of the oxygen reacted at all, while 100cm³ comes from wrongly doubling the hydrogen volume instead of halving it to find the oxygen needed.

6. 6.

   SO$_2$ + O$_2$ 2SO$_3$

   In the reaction above, the most suitable catalyst is?

   1. A
      Platinum
   2. B
      Vanadium(V) oxide
      Correct
   3. C
      Nickel
   4. D
      Iron
   Show answerHide answer

   Answer: B

   The equation SO₂ + O₂ → 2SO₃ is the central step of the Contact Process, which is how sulfuric acid (H₂SO₄) is manufactured industrially. This oxidation of sulfur(IV) oxide to sulfur(VI) oxide is catalysed by vanadium(V) oxide (V₂O₅), which is the correct answer.

   So for this specific step of sulfuric acid production, the correct catalyst is vanadium(V) oxide.

7. 7.

   Addition of sodium chloride to water to form a solution would lead to?

   1. A
      Increase in freezing point and decrease in boiling point
   2. B
      Decrease in freezing point and decrease in boiling point
   3. C
      Decrease in freezing point and increase in boiling point
      Correct
   4. D
      Increase in freezing point and increase in boiling point
   Show answerHide answer

   Answer: C

   Dissolving sodium chloride in water is a colligative property effect. The Na⁺ and Cl⁻ ions get in the way of the water molecules arranging into ice and escaping as vapour, so both boundary temperatures of the solution shift away from those of pure water at the same time.

   Decrease in freezing point and increase in boiling point is correct: the dissolved ions lower the vapour pressure, which depresses the freezing point (this is why salt is spread on icy roads, to stop water freezing at 0°C) and elevates the boiling point (salted water boils above 100°C).

8. 8.

   The following non-metal form acidic oxides with oxygen except?

   1. A
      Phosphorus
   2. B
      Carbon
   3. C
      Hydrogen
      Correct
   4. D
      Nitrogen
   Show answerHide answer

   Answer: C

   Non-metals generally react with oxygen to form acidic oxides - oxides that dissolve in water to give an acid and turn blue litmus paper red.

   Carbon forms CO₂, which dissolves in water to form carbonic acid (H₂CO₃) - acidic.
   Nitrogen forms oxides such as NO₂ and N₂O₅, which give nitric/nitrous acid - acidic.
   Phosphorus forms P₄O₁₀, which reacts with water to give phosphoric acid (H₃PO₄) - acidic.

   Hydrogen, on the other hand, combines with oxygen to form water (H₂O). Water is a neutral oxide, not an acidic one - it does not behave as an acid and does not turn litmus red. So among these non-metals, hydrogen is the one whose oxide with oxygen is not acidic.

9. 9.

   How many bonding pair are present in carbon(iv)oxide?

   1. A
      4
      Correct
   2. B
      8
   3. C
      2
   4. D
      6
   Show answerHide answer

   Answer: A

   Carbon(iv)oxide, CO₂, has the structure O=C=O. Carbon shares a double bond with each of the two oxygen atoms.

   Each double bond is made up of 2 shared (bonding) electron pairs — one sigma pair and one pi pair. Since there are two double bonds in the molecule:

   2 double bonds × 2 bonding pairs each = 4 bonding pairs in total.

   So the correct number of bonding pairs in CO₂ is 4.

10. 10.

    In the extraction of iron, hot air is introduced into the blast furnacethrough?

    1. A
       The slag notch
    2. B
       The hopper
    3. C
       The tuyeres
       Correct
    4. D
       The tap hole
    Show answerHide answer

    Answer: C

    The tuyeres are correct. In the blast furnace used to extract iron, hot air (the "blast") is blown into the furnace through a set of nozzles called tuyeres, positioned near the base of the furnace. This hot air reacts with the coke to produce heat and carbon(IV) oxide, which is then reduced to carbon(II) oxide, the main reducing agent that converts iron(III) oxide to molten iron.

    So only the tuyeres carry the hot air blast into the furnace.

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

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