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 691: Which of the following equilibria shows little or no net reaction when the volume of the system is decreased? Options:
  A) H_2(g) + I_2(g) ≈ 2HI_(g)
  B) 2NO₂^(g) ≈ N₂O_4(g)O_4(g)N₂O_4(g)
  C) PCI_5(g) ≈ PCI_3(g) + CI_2(g)
  D) ZnO_(s) + CO_2(g) ≈ ZnCO_3(g)
  Show Answer
  The correct answer is D .
• Question 692:

  Which of the following is the electronic configuration of sodium?

  (Atomic number of Na = 11)

  Options:
  A) 1s² 2s²2p⁶ 3s²
  B) 1s² 2s²2p⁶ 3s² 3p1s² 2s²2p⁶ 3s¹
  C) 1s² 2s²2p⁶ 3s¹
  D) 1s² 2s²2p⁶ 3s^°
  E) 1s² 2s²2p⁶ 4s¹
  Show Answer
  The correct answer is C .
• Question 693:

  A sample of any of the following substances disappearsafter some time when exposed to air like camphor, naphthalene, or dry ice. This phenomenon is called?

  Options:
  A) Sublimation
  B) Evaporation
  C) Diffusion
  D) Radiation
  Show Answer
  The correct answer is A .
• Question 694: Addition of an aqueous solution of a salt gives a white precipitate. The salt is likely to be a? Options:
  A) nitrate
  B) carbonate
  C) chloride
  D) sulphide
  Show Answer
  The correct answer is B .
• Question 695: According to Charle's law, the volume of a gas becomes zero at Options:
  A) −100°c
  B) −273°c
  C) −373°c
  D) 0°c
  Show Answer
  The correct answer is B .
• Question 696: There are basic particles from which matter called be made except Options:
  A) Salt
  B) Atom
  C) Ion
  D) Molecule
  Show Answer
  The correct answer is A .
• Question 697: The acid used in electrolysis of water is dilute Options:
  A) HNO₃
  B) CH₃COOH
  C) H₂SO₄
  D) HCl
  Show Answer
  The correct answer is C .
• Question 698:

  Which of the following is a primary constituent of crude oil?

  Options:
  A) Pentane
  B) Ethanol
  C) Heptane
  D) Methane
  Show Answer
  The correct answer is D .
• Question 699: Which of the following molecules has two other positional isomers? Options:
  A) CH₃CH₂Br
  B) CH₃CHBrCH₃
  C) CBr₂F₂
  D) CH₂CHBrCH₂Br
  Show Answer
  The correct answer is D .
• Question 700:

  Which of the following reactions would be expected to have the highest entropy change?

  Options:
  A) Liquid → Gas
  B) Solid → Liquid
  C) Gas → Liquid
  D) Gas → Solid
  Show Answer
  The correct answer is A .