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 1971: The electron configuration of ₂₂X ²⁺ ion is Options:
  A) 1s² 2s²2p⁶ 3s² 3p⁶ 4s² 3d²
  B) 1s² 2s²2p⁶ 3s² 3p⁶ 4s² 3d¹
  C) 1s² 2s²2p⁶ 3s² 3p⁶
  D) 1s² 2s²2p⁶ 3s² 3p⁶ 4s²
  Show Answer
  The correct answer is D .
• Question 1972:

  What is the mass percentage of carbon (C) in methane (CH4)? (The molar mass of carbon is approximately 12 g/mol.)

  Options:
  A) 25%
  B) 12%
  C) 75%
  D) 50%
  Show Answer
  The correct answer is C .
• Question 1973: A major effect of oil pollution in coastal waters is the? Options:
  A) destruction of marine life
  B) desalination of the water
  C) increase in the acidity of the water
  D) detoxification of the water
  Show Answer
  The correct answer is C .
• Question 1974: CO_g + H₂O_g $\to$ _2g + H_2g $\mathrm{\Delta }$H = -4100J. Which of the following factors favour the formation of hydrogen in the above reaction? i. high pressure. ii. low pressure iii. high temperature iv. use of excess steam Options:
  A) i, iii and iv
  B) iii only
  C) ii, iii and i
  D) iv only
  Show Answer
  The correct answer is D .
• Question 1975: Ethanol reacts with aqueous sodium mono-oxoio date (l) to give a bright yellow solid with a characteristic smell. The product is? Options:
  A) trichloromethane
  B) triodomethane
  C) iodoethane
  D) ethanal
  Show Answer
  The correct answer is B .
• Question 1976: Which of the following separation processes is most likely to yield high quality ethanol (>95%) from palm wine? Options:
  A) Fractional distillation without a dehydrant
  B) simple distillation with a dehydrant
  C) fractional distillation with a dehydrant
  D) column chromatography
  E) evaporation
  Show Answer
  The correct answer is C .
• Question 1977: A blue solid, T, which weighed 5.0g was placed on a table. After 8 hours, the resulting pink solid was found to weigh 5.5g. It can be inferred that substance T? Options:
  A) is deliquescent
  B) is hydroscopic
  C) has some molecules of water of crystallization
  D) is efflorescent
  Show Answer
  The correct answer is A .
• Question 1978: The reaction 3C(s) + 2Fe₂O₃(s) = 4Fe(s) + 3CO₂(g): $\mathrm{\Delta }$H =46.0 kJ is Options:
  A) isothermic
  B) adiabatic
  C) isobaric
  D) endothermic
  E) exothermic
  Show Answer
  The correct answer is D .
• Question 1979: When chlorine gas is passed into a solution of sulphur dioxide? Options:
  A) sulphur dioxide is reduced to sulphur
  B) the chlorine is oxidized to hydrochloric acid
  C) dilute sulphuric acid and hydrochloric acid are produced
  D) Hydrochloric acid and sulphur are produced
  E) sulphur trioxide is the only product
  Show Answer
  The correct answer is C .
• Question 1980: Kerosine is commonly used to remove the red colour stain of palm oil from cloths because it Options:
  A) helps to spread the oil over a larger surface area
  B) react with the oil to form an odourless compound
  C) makes the oil evaporate easily by dissolving it
  D) helps to dilute the oil and reduce its colour
  Show Answer
  The correct answer is C .