JAMB Chemistry 2015 past questions

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

Ten questions from the 2015 JAMB Chemistry paper, with answers and explanations. We hold 28 questions from this paper, and the Skolra app has all of them.

JAMB Chemistry 2015 questions and answers

1. 1.Which of the activities is commonly used as a nuclear fuel
   1. A
      carbon-14
   2. B
      hydrogen-1
   3. C
      uranium-235
      Correct
   4. D
      radium-226
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   Answer: C

   Uranium-235 (²³⁵U) is the most widely used nuclear fuel. It is fissile: when struck by slow (thermal) neutrons it undergoes nuclear fission, splitting into lighter nuclei and releasing a very large amount of energy. This makes it the fuel of choice in the majority of commercial nuclear power reactors worldwide.

2. 2.A change in the temperature of a saturated solution disturbs the equilibrium between the
   1. A
      solvent and undissolved solute
   2. B
      solvent and dissolved solute
   3. C
      saturated solution and unsaturated solution
   4. D
      dissolved solute and undissolved solute
      Correct
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   Answer: D

   A saturated solution exists at equilibrium between the dissolved solute and the undissolved solute. Any change in temperature disturbs this balance: raising the temperature generally increases solubility and shifts the equilibrium toward more dissolved solute, while lowering the temperature decreases solubility and causes solute to crystallise out.

3. 3.

   Chlorine, consisting of two isotopes of mass numbers 35 and 37, has an atomic mass of 35.5.

   The relative abundance of the isotope of mass number 37 is?

   1. A
      75%
   2. B
      25%
      Correct
   3. C
      12.5%
   4. D
      50%
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   Answer: B

   Let the fractional abundance of the ³⁷Cl isotope be x, so the abundance of ³⁵Cl is (1 − x). Setting up the weighted average: 35(1 − x) + 37x = 35.5. Expanding gives 35 + 2x = 35.5, so 2x = 0.5 and x = 0.25. The relative abundance of the isotope of mass number 37 is therefore 25%.

4. 4.Which of these require crystallization most?
   1. A
      copper(II) sulphate
      Correct
   2. B
      river sand
   3. C
      petrol
   4. D
      ethanol
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   Answer: A

   Copper(II) sulphate is the substance that most classically requires crystallization for purification. Its solubility is strongly temperature-dependent: it dissolves freely in hot water but deposits large, well-formed blue crystals on cooling. Distillation is unsuitable because the salt decomposes on heating to very high temperatures, making recrystallization the standard purification method.

5. 5.Tartaric acid is used industrially to
   1. A
      stabilize wine and as a food acidulant
      Correct
   2. B
      produce fertilizers and pesticides
   3. C
      manufacture synthetic rubber
   4. D
      refine crude petroleum
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   Answer: A

   Tartaric acid is a naturally occurring dicarboxylic acid found in grapes. Its main industrial applications are as an acidulant and antioxidant synergist in food and beverages — imparting a tart flavour — and as a stabilizer in wine production where it prevents unwanted chemical changes. It is also the parent compound of cream of tartar (potassium hydrogen tartrate) used in baking.

6. 6.The oxidation state of oxygen in tetraoxosulphate (VI) acid is
   1. A
      +2
   2. B
      -1
   3. C
      -2
      Correct
   4. D
      +6
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   Answer: C

   In almost all compounds, oxygen carries an oxidation state of −2. In tetraoxosulphate(VI) acid (H₂SO₄), each of the four oxygen atoms has an oxidation state of −2, giving sulfur an oxidation state of +6 — consistent with the (VI) designation in the IUPAC name.

7. 7.What volume of 0.5 M H₂SO₄ will exactly neutralize 20 cm³ of 0.1 M NaOH Solution?
   1. A
      2 cm³
      Correct
   2. B
      4 cm³
   3. C
      10 cm³
   4. D
      40 cm³
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   Answer: A

   The neutralization equation is H₂SO₄ + 2NaOH → Na₂SO₄ + 2H₂O, giving a 1:2 acid-to-base molar ratio. Moles of NaOH = 0.1 mol dm⁻³ × 0.020 dm³ = 0.002 mol. Moles of H₂SO₄ required = 0.002 ÷ 2 = 0.001 mol. Volume of 0.5 M H₂SO₄ = 0.001 ÷ 0.5 = 0.002 dm³ = 2 cm³.

8. 8.

   A small quantity of solid ammonium chloride (NH₄Cl) was heated gently in a test tube, the solid gradually disappears to produce two gases. Later, a white cloudy deposit was observed on the cooler part of the test tube. The ammonium chloride is said to have undergone

   1. A
      combustion
   2. B
      sublimation
      Correct
   3. C
      evaporation
   4. D
      dissolution
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   Answer: B

   When ammonium chloride is heated, it undergoes sublimation — it converts directly from solid to vapour without passing through a liquid phase: NH₄Cl(s) ⇌ NH₃(g) + HCl(g). The two gases travel up to the cooler upper part of the test tube where they recombine and deposit as a white solid. This direct solid-to-gas-to-solid cycle is the defining characteristic of sublimation.

9. 9.

   Two equal bulbs, one containing ammonia and the other nitrogen are opened mouth-to-mouth to each other at room temperature. The entropy in the mixture of gases is likely to

   1. A
      decrease
   2. B
      remain constant
   3. C
      increase
      Correct
   4. D
      become zero
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   Answer: C

   When two different gases are allowed to mix, the number of possible arrangements (microstates) of the molecules increases enormously. By the second law of thermodynamics, this greater disorder corresponds to an increase in entropy. Mixing is a spontaneous, irreversible process driven by the increase in disorder, and it occurs regardless of whether the gases are ideal.

10. 10.Electronic configuration of an elements 13x in the subsidiary energy level is
    1. A
       1s² 2s² 2p⁶ 3s¹ 3p²
    2. B
       1s² 2s² 2p⁶ 3s² 3d¹
    3. C
       1s² 2s² 2p⁶ 3s² 3p¹
       Correct
    4. D
       1s² 2s² 2p⁵ 3s² 3p²
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    Answer: C

    Element 13 is aluminium (Al) with 13 electrons. Filling the subshells in order of increasing energy: 1s takes 2, 2s takes 2, 2p takes 6, 3s takes 2, and the remaining 1 electron enters 3p. The full subshell (subsidiary energy level) configuration is therefore 1s² 2s² 2p⁶ 3s² 3p¹.

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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