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:

  An organic compound contains 69% carbon, 15.3% hydrogen and 30.7% oxygen. Calculate the the empirical formula [C=12, H = 1, O = 16]

  Options:
  A) C${}_4$H${}_{1}2$O
  B) C${}_3$H${}_9$O
  C) C${}_4$H${}_9$O
  D) C${}_3$H${}_8$O
  Show Answer
  The correct answer is D .
• Question 692: In countries where the temperature falls below 273K, salt is always sprinkled on the icy road in order to Options:
  A) lower the melting point of the ice
  B) increase the density of the ice
  C) make the ice impure
  D) raise the melting point of the ice
  Show Answer
  The correct answer is A .
• Question 693: When copper (ii) sulphate solution is treated with excess ammonium hydroxide, a precipitate is first formed, and then this dissolves to give a deep blue solution. This deep blue solution is a Options:
  A) Cu(OH)₂
  B) CuSo₄.5H₂O
  C) (NH₄)₂SO₄
  D) Cu(NH₃)₄(OH)₂
  E) CuSO₄.(NH₄)₂SO₄.2H₂O
  Show Answer
  The correct answer is E .
• Question 694: The shape of the carbon (lV) oxide molecule is Options:
  A) pyramidal
  B) linear
  C) angular
  D) tetrahedral
  Show Answer
  The correct answer is B .
• Question 695:

  What number of moles of Cu ²⁺ will be deposited by 360 coulombs of electricity?

  [f = 96500 C mol ^-1]

  Options:
  A) 5.36 x 10 ^-4 mole
  B) 1. 87 x 10 10 ^-3 mole
  C) 9. 35 x 10 ^-4 mole
  D) 3. 73 x 10 ^-3
  Show Answer
  The correct answer is B .
• Question 696: The ion that will give a white precipitate with aqueous NaOH and soluble in excess of the base is Options:
  A) Ca²⁺
  B) Mg²⁺
  C) Zn²⁺
  D) Cu²⁺
  Show Answer
  The correct answer is C .
• Question 697: Which of the following compounds will undergo polymerization reaction? Options:
  A) C₂H₄
  B) C₂H₅COOH
  C) C₂H₆
  D) C₂H₅OH
  Show Answer
  The correct answer is A .
• Question 698: The correct order of increasing boiling points of the following compounds C₃H₇OH, C₇H₁₆ and C₄H₁₀ is Options:
  A) C₃H₇OH → C₄H₁₀ → C₇H₁₀
  B) C₄H₁₀ → C₇H₁₆ → C₃H₇OH
  C) C₇H₁₆ → C₃H₇OH → C₄H₁₀
  D) C₄H₁₀ → C₃H₇OH → C₇H₁₆
  Show Answer
  The correct answer is D .
• Question 699: For a gas, the relative molecular mass is equal to 2Y. What is Y? Options:
  A) The mas of the gas
  B) The vapour density of the gas
  C) The volume of the gas
  D) The temperature of the gas
  Show Answer
  The correct answer is B .
• Question 700: When sugar is dissolved in tea, the reaction is always accomplished by Options:
  A) positive change
  B) negative entropy change
  C) no entropy change
  D) a minimum entropy change
  Show Answer
  The correct answer is C .