WAEC Chemistry 2017 past questions

Checked by the Skolra question team · Last updated 15 October 2026

Ten questions from the 2017 WAEC Chemistry paper, with answers and explanations. We hold 50 questions from this paper, and the Skolra app has all of them.

WAEC Chemistry 2017 questions and answers

1. 1.

   Soluble salts can be prepared by the following methods except

   1. A
      neutralization of an acid with a base
   2. B
      direct combination of elements
   3. C
      displacement of a metal from its salt solution
   4. D
      precipitation
      Correct
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   Answer: D

   Precipitation is a method used specifically for preparing insoluble salts: two soluble solutions are mixed, and the insoluble salt forms as a solid precipitate. Since the desired product must be insoluble to be collected this way, precipitation cannot be used to prepare soluble salts. Neutralization, direct combination, and displacement can all yield soluble products.

2. 2.

   Which of the following statements about endothermic reaction is correct?

   1. A
      The enthalpy change is positive
      Correct
   2. B
      The products have less energy than the reactants
   3. C
      The temperature of the reaction mixture increases
   4. D
      Heat is released to the surroundings
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   Answer: A

   In an endothermic reaction, energy is absorbed from the surroundings. The products have more energy than the reactants, so the enthalpy change (ΔH) is positive. Heat flows into the system, so the temperature of the surroundings decreases, not increases.

3. 3.

   The seperation of Nitrogen from oxygen using fractional distillation of air is possible because

   1. A
      Nitrogen is much lighter than oxygen
   2. B
      Nitrogen and oxygen have different boiling points
      Correct
   3. C
      Oxygen is more soluble in liquid air than nitrogen
   4. D
      Nitrogen and oxygen react differently with catalysts
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   Answer: B

   Fractional distillation separates components of a mixture based on differences in their boiling points. Nitrogen boils at −196°C and oxygen boils at −183°C. When liquefied air is gradually warmed, nitrogen (having the lower boiling point) vaporises first and can be collected separately from oxygen.

4. 4.

   The name of the compound $C_{4}H_{9}COOC_{3}H_{7}$ is

   1. A
      Propyl butanoate
   2. B
      Butyl propanoate
   3. C
      Propyl pentanoate
      Correct
   4. D
      Pentyl propanoate
   Show answerHide answer

   Answer: C

   In IUPAC ester nomenclature, the alkyl group derived from the alcohol is named first, followed by the carboxylate part from the acid. C₄H₉COO– contains five carbons in the acid chain (including the carbonyl carbon), corresponding to pentanoic acid. The –C₃H₇ group is the propyl group from propan-1-ol. The compound is therefore propyl pentanoate.

5. 5.

   Graphite and Diamond are similar in that they

   1. A
      Have identical physical properties
   2. B
      Are both good conductors of electricity
   3. C
      Have the same crystal structure
   4. D
      Are both made entirely of carbon atoms
      Correct
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   Answer: D

   Graphite and diamond are both allotropes of carbon — they are both composed entirely of carbon atoms. They differ fundamentally in their bonding arrangements: diamond has a giant tetrahedral covalent lattice, while graphite has a layered structure with delocalised electrons between planes, giving them very different physical properties.

6. 6.

   The condensation of two units of glucose will produce a dissacharide with the formula $C_{12}H_{22}O_{11}$ which is

   1. A
      Lactose
   2. B
      Maltose
      Correct
   3. C
      Galactose
   4. D
      Sucrose
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   Answer: B

   When two glucose molecules undergo a condensation reaction, one water molecule is eliminated and a glycosidic bond forms between them, producing the disaccharide maltose (C₁₂H₂₂O₁₁). Sucrose is formed from glucose and fructose, lactose from glucose and galactose, and galactose is itself a monosaccharide, not a disaccharide.

7. 7.

   A hydrocarbon contained 14.3% hydrogen. The empirical formula for the hydrocarbon is [H= 1.0, C= 12.0]

   1. A
      CH₂
      Correct
   2. B
      CH
   3. C
      CH₄
   4. D
      CH₃
   Show answerHide answer

   Answer: A

   Hydrogen is 14.3% so carbon is 85.7%.
   Moles of H = 14.3 ÷ 1.0 = 14.3
   Moles of C = 85.7 ÷ 12.0 = 7.14
   Ratio H : C = 14.3 : 7.14 ≈ 2 : 1
   The empirical formula is therefore CH₂.

8. 8.

   The use of diamond in abrasives is due to its

   1. A
      Transparency
   2. B
      Extreme hardness
      Correct
   3. C
      Electrical conductivity
   4. D
      High melting point
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   Answer: B

   Diamond is the hardest naturally occurring substance, rated 10 on the Mohs hardness scale. This extreme hardness, which arises from its giant tetrahedral covalent network structure, makes it ideal for cutting tools and abrasives where it can wear down virtually any other material.

9. 9.

   The following glasswares are used to measure the volume of liquids EXCEPT

   1. A
      Burette
   2. B
      Measuring cylinder
   3. C
      Pipette
   4. D
      Conical flask
      Correct
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   Answer: D

   A burette, pipette, and measuring cylinder are all calibrated glassware designed for accurate volume measurement. A conical flask (Erlenmeyer flask) is used as a reaction vessel — for example, to hold the solution being titrated — but it is not calibrated for precise volume measurement and is therefore not a volumetric instrument.

10. 10.

    Which of the following gases is not acidic?

    1. A
       Hydrogen chloride (HCl)
    2. B
       Carbon dioxide (CO₂)
    3. C
       Ammonia (NH₃)
       Correct
    4. D
       Sulphur dioxide (SO₂)
    Show answerHide answer

    Answer: C

    Acidic gases dissolve in water to form acidic solutions. Ammonia (NH₃) dissolves in water to form ammonium hydroxide, an alkaline solution, making it a basic gas. Carbon dioxide, hydrogen chloride, and sulphur dioxide all produce acidic solutions when dissolved in water.

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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