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 71: When the kerosene fraction from petrol is heated at high temperature, a lower boiling liquid is obtained. This process is known as Options:
  A) polymerization
  B) refining
  C) hydrogenation
  D) cracking
  Show Answer
  The correct answer is D .
• Question 72: 2X_(g) + Y_(g) → Z_(g): In the equation above, The rate of formation of Z is found to be independent of the concentration of Y and to quadruple when the concentration of X is doubled. The correct equation for the reaction is? Options:
  A) R = k (X)(Y)
  B) R = K (X) ° (Y)
  C) R = K (X) ° (Y) ₂
  D) R = K (X) ₂(Y)°
  Show Answer
  The correct answer is D .
• Question 73: In a chemical reaction, the change in concentration of a reactant with time is Options:
  A) entropy of reaction
  B) enthalpy of reaction
  C) rate of reaction
  D) order of reaction
  Show Answer
  The correct answer is C .
• Question 74: Which of these represents a redox reaction? Options:
  A) AgNO₃ + NaCl → AgCAl + NaNO₃
  B) H₂S + Pb(NO₃) → PbS + 2HNO₃
  C) CaCO₃ → CaO + CO₂
  D) Zn + 2HCl → ZnCl₂ + H₂
  Show Answer
  The correct answer is D .
• Question 75:

  A colored gas that is known to be poisonous and can readily damage the mucous liningof the lungs is?

  Options:
  A) hydrogen sulphide
  B) carbon(ii)oxide
  C) chlorine
  D) sulphur(iv)oxide
  Show Answer
  The correct answer is C .
• Question 76: The highest rate of production of carbon (lV) oxide can be achieved using Options:
  A) 0.05 mol ^-3HCI and 5g powdered CaCO₃
  B) 0.05 mol ^-3HCI and 5g lump CaCO₃
  C) 0.10 mol ^-3HCI and 5g powdered CaCO₃
  D) 0.025 mol ^-3HCI and 5g powdered CaCO₃
  Show Answer
  The correct answer is C .
• Question 77:

  Sodium sulphate decahydrate (Na₂SO₄.10 H₂O) on exposure to air loses all its water of crystallization.

  The process of loss is known as

  Options:
  A) efflorescence
  B) hygroscopy
  C) deliquescence
  D) effervescence
  E) dehydration
  Show Answer
  The correct answer is A .
• Question 78: The pH of four solutions W, X, Y, Z are 4, 6, 8, 10 respectively, therefore Options:
  A) none of these solutions is acidic
  B) the pH of Y is made more acidic by addition of distilled water
  C) Z is the most acidic solution
  D) W is the most acidic solution
  E) X is neutral
  Show Answer
  The correct answer is D .
• Question 79: Which of the following fraction is used as raw material for the cracking process? Options:
  A) kerosine
  B) lubricating oil
  C) bitumen
  D) diesel oils
  Show Answer
  The correct answer is D .
• Question 80: The number of atoms of chlorine present in 5.85g of NaCl is [Avogaro's Number = 6.02 x 10²³] Options:
  A) 6.02 x 10²²
  B) 5.85 x 10²³
  C) 6.02 x 10²³
  D) 5.85 x 10²⁴
  Show Answer
  The correct answer is A .