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 81:

  Cr₂O₇^2-_(aq) + 14H⁺_(aq) + 6l^-_(aq) → 2Cr³⁺_(aq) + 3l_(g) + 7H₂O_(I).

  The change in the oxidation number of oxygen in the equation above is?

  Options:
  A) 1
  B) 2
  C) 7
  D) 0
  Show Answer
  The correct answer is D .
• Question 82: How many Faraday of electricity are required to deposit 0.20 mole of nickel, if 0.10 Faraday of electricity deposited 2.98g of nickel during electrolysis of its aqueous solution?(Ni = 58.7, 1F = 96 500 C mol^-) Options:
  A) 0.20
  B) 0.30
  C) 0.40
  D) 0.50
  Show Answer
  The correct answer is C .
• Question 83:

  C_(s) + 2S_(g) → CS_2(g)

  ΔH = +89 kJ mol^-1

  The chemical equation above implies that

  Options:
  A) each of carbon and sulphur has 89 kJ of energy
  B) both carbon and sulphur contribute 89 kJ of energy
  C) 89 kJ of energy is released
  D) 89 kJ of energy is absorbed
  Show Answer
  The correct answer is D .
• Question 84:

  Which of the following is the best starting material for the preparation of oxygen? Heating of trioxonitrate (v) with

  Options:
  A) Pb
  B) Zn
  C) Ca
  D) Na
  Show Answer
  The correct answer is A .
• Question 85:

  Which of the following gases contains the least number of atoms at s.t.p?

  Options:
  A) 1 mole of butane
  B) 4 moles of chlorine
  C) 3 moles of ozone
  D) 7 moles of argon
  Show Answer
  The correct answer is A .
• Question 86: When temporary hard water is boiled for sometime in a kettle, the inner surface of the kettle becomes coated with a deposit of Options:
  A) calcium tetraoxosulphate(VI)
  B) calcium trioxocarbonate (IV)
  C) calcium hydrogentrioxocarbonate (IV)
  D) aluminium trioxocarbonate (IV)
  Show Answer
  The correct answer is B .
• Question 87:

  What happens to the value of the equilibrium constant (Kc) for a reaction if the reaction is reversed?

  Options:
  A) It becomes zero
  B) It becomes negative
  C) It remains the same
  D) It becomes the reciprocal of the original value
  Show Answer
  The correct answer is D .
• Question 88: In the electrolysis of brine the anode is Options:
  A) platinum
  B) copper
  C) zinc
  D) carbon
  Show Answer
  The correct answer is D .
• Question 89:

  A gas occupies a volume of 1.5 liters at a pressure of 2 atmospheres. If the pressure is increased to 4 atmospheres while the temperature remains constant, what will be the new volume of the gas?

  Options:
  A) 6 liters
  B) 1.5 liters
  C) 0.75 liters
  D) 3 liters
  Show Answer
  The correct answer is C .
• Question 90:

  Equal volumes of CO,SO₂, and H₂S were released into a room at the same point and time. Which of the following gives the order of diffusion of the gases to the opposite corner of the room?

  (S = 32, C = 12, O = 16, N = 14, H = 1)

  Options:
  A) CO, SO₂,NO₂,H₂S
  B) SO₂,NO₂,H₂S,CO
  C) CO,H₂S,SO₂,NO₂
  D) CO,H₂S,NO₂,SO₂
  Show Answer
  The correct answer is D .