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 21:

  Isotopes of an element have

  Options:
  A) The same number of protons but different numbers of neutrons.
  B) The same number of neutrons and electrons
  C) The same number of protons and neutrons
  D) The same number of protons and electrons
  Show Answer
  The correct answer is A .
• Question 22: Which of the following represents a precipitation reaction? Options:
  A) H₂SO₄ + NaCl $\to$ NaHSO₄ + HCl
  B) Fe +H₂SO₄ $\to$ FeSO₄ + H₂
  C) 4HCl + MnO₂ $\to$ MnCl₂ + 2H₂O + Cl₂
  D) Na₂SO₄ + pb(NO₃) $\to$ PbSO₄ + 2NaNO
  E) CuO +2HCl $\to$ Cl₂ + H₂O
  Show Answer
  The correct answer is D .
• Question 23: The octane number of a fuel whose performance is the same as that of a mixture of 55 g of 2,2,4- trimethly pentane and 45 g of n-heptane is ? Options:
  A) 45
  B) 55
  C) 80
  D) 100
  Show Answer
  The correct answer is B .
• Question 24: The air around a petroleum refinery is most likely to contain? Options:
  A) CO₂, SO₃ and N₂O
  B) CO₂, CO and N₂O
  C) SO₂, CO and NO₂
  D) PH₃ H₂O and CO₂
  Show Answer
  The correct answer is C .
• Question 25: When excess ethanol is heated to 145^oC in the presence of concentrated H₂SO₄, the product is Options:
  A) ethyne
  B) diethyl sulphate
  C) diethyl ether
  D) acetone
  Show Answer
  The correct answer is C .
• Question 26: If 10.8 g of silver is deposited in a silver coulometer volume of oxygen liberated is? Options:
  A) 0.56 dm³
  B) 5.60 dm³
  C) 11.20 dm³
  D) 22.40 dm³
  Show Answer
  The correct answer is A .
• Question 27:

  The heat required to raise the temperature of the body by 1k is called?

  Options:
  A) Specific heat
  B) Thermal capacity
  C) Water equivalent
  D) None of the above
  Show Answer
  The correct answer is B .
• Question 28:

  What volume of gas is evolved at S.t.p if 2g of calcium trioxocarbonate (IV) is added to a solution of hydrochloric acid?

  [Ca = 40, C = 12, O = 16, Cl = 35.5, H = 1 Molar volume of agas at s.t.p = 22.4 dm³

  Options:
  A) 112 cm²
  B) 224 cm²
  C) 448 cm²
  D) 2240 cm²
  Show Answer
  The correct answer is C .
• Question 29:

  Which of the following is a physical change?

  Options:
  A) Exposing white phosphorus to air
  B) Burning kerosene
  C) Dissolving calcium in water
  D) Freezing ice cream
  Show Answer
  The correct answer is D .
• Question 30: Sodium hydroxide (NaOH) pellets are Options:
  A) deliquescent
  B) hygroscopic
  C) efflorescent
  D) hydrated
  E) fluorescent
  Show Answer
  The correct answer is A .