Chemistry Exam Past Questions and Answers | JAMB, WAEC and NECO

Chemistry is the study of the substances that make up matter. It looks at their properties, how they react with each other, and how these reactions can create new substances.

• Question 1:

  Which organic compound is responsible for the characteristic aroma of fruits?

  Options:
  A) Alkane
  B) Alkyne
  C) Ester
  D) Amine
  Show Answer
  The correct answer is C .
• Question 2:

  The following are isoelectronic ions except

  Options:
  A) Na${}^{+}$
  B) Mg${}^{2+}$
  C) Si${}^{2+}$
  D) O${}^{2+}$
  Show Answer
  The correct answer is C .
• Question 3: Which of the following gases is the most dangerous pollutant? Options:
  A) Hydrogen sulphide
  B) Carbon (lV) oxide
  C) Sulphur (lV) oxide
  D) Carbon (ll) oxide
  Show Answer
  The correct answer is D .
• Question 4: The Avogadro number of 24g of magnesium is the same as that of Options:
  A) 1g of hydrogen molecules
  B) 16g of oxygen molecules
  C) 32g of oxygen molecules
  D) 35.5g of chlorine molecules
  Show Answer
  The correct answer is C .
• Question 5: The atomic radius of Li, Na and K are 1: 33A, 1. 54A and 1. 96A res pectively. Which of the following explaqins this gradation in atomic radius? Options:
  A) electropositivity decreases from Li to Na to K
  B) electronegativity decreases from Li to Na to K
  C) the number of the electron shells increases from Li to Na to K
  D) the elements are in the same period
  Show Answer
  The correct answer is C .
• Question 6: If 100cm³ of oxygen pass through a porous plug is 50 seconds, the time taken for the same volume of hydrogen to pass through the same porous plug is? [O = 16, H = 1] Options:
  A) 10.0s
  B) 12.5s
  C) 17.7s
  D) 32.0s
  Show Answer
  The correct answer is B .
• Question 7: The correct order of increasing oxidation number of the transition metal ions for the compounds K₂Cr₂O₇, V₂O₅ and KMnO₄ is Options:
  A) V₂O₅< K_2Cr2O₇< KMnO₄
  B) K₂Cr₂O₇< KMnO_{4 < V2O5}
  C) KMnO₄< K_2Cr2O₇< V_2O5
  D) KMnO₄< V_2O5< K_2Cr2O₇
  Show Answer
  The correct answer is A .
• Question 8: The relative atomic mass of a naturally occurring lithium consisting of 90% Li and 10% Li is Options:
  A) 6.9
  B) 7.1
  C) 6.2
  D) 6.8
  Show Answer
  The correct answer is C .
• Question 9: What volume of 0.5 mol dm^-3 H₂SO₄ will exactly neutralize 20cm³ of 0.1 mol dm^-3 NaOH solution? Options:
  A) 2.0 cm³
  B) 5.0 cm³
  C) 6.8 cm³
  D) 8.3 cm³
  Show Answer
  The correct answer is A .
• Question 10: 9.8g of solid potassium chlorate (KCIO₃) were added to 40 cm³ of water and heated to dissolve all the solid. As he solution cooled, crystals of potassium chlorate started forming at 60°C. The solubility of potassium chlorate at 66°C is therefore? Options:
  A) 24.5 mole per dm³
  B) 0.2 mole per dm³
  C) 10.0 mole per dm³
  D) 20.0 mole per dm³
  E) 2.0 mole per dm³
  Show Answer
  The correct answer is E .