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 1841: In two separate experiments, 0.36g and 0.71g of chlorine combined with a metal X to give Y and Z respectively. An analysis showed that Y and Z contain 0.20g and 0.40g of X respectively. The data above represents the law of ? Options:
  A) multiple proportion
  B) conservation of mass
  C) constant composition
  D) reciprocal proportion
  Show Answer
  The correct answer is C .
• Question 1842: The general formula for the alkanals is Options:
  A) ROH
  B) R₂CO
  C) RCOOR¹
  D) RCHO
  Show Answer
  The correct answer is D .
• Question 1843:

  For the reaction NH₄NO₂ $\to$ N₂ + 2H₂O, calculate the volume of nitrogen that would be produced at S. T. P from 320 g of the dioxonitrate(iii)salt. (Relative atomic masses: N = 14, O = 16, H = 1)

  Options:
  A) 2.24 dm ³
  B) 224 dm³
  C) 1.12 dm ³
  D) 112 dm ³
  E) 4.48 dm ³
  Show Answer
  The correct answer is D .
• Question 1844:

  When an acidic solution is diluted, what happens to its pH?

  Options:
  A) It depends on the specific acid
  B) It decreases
  C) It remains the same
  D) It increases
  Show Answer
  The correct answer is D .
• Question 1845: Argon is used in gas-filled electric lamp because it helps to? Options:
  A) prevent the reduction of the lamp fillaments
  B) prevent oxidation of the lamp fillaments
  C) make the lamp fillament glow brightly
  D) keep the atmosphere in the lamp inert
  Show Answer
  The correct answer is C .
• Question 1846: Carbon is tetravalent because Options:
  A) The electrons in both the 2s and 2p orbitals are equivalent
  B) The electrons in all the orbitals of carbon are equivalent
  C) The 2s and 2p atomic orbitals hybridize
  D) All the atomic orbitals of carbon hybridize
  Show Answer
  The correct answer is A .
• Question 1847: 2CL^-_(aq) → CI_2(g) + 2e^-(aq). The above half-cell reaction occuring at the anode during the electrolysis of dilute ZnCI₂ solution is? Options:
  A) ionization
  B) oxidation
  C) reduction
  D) recombination
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  The correct answer is B .
• Question 1848: The fraction of crude oil used as jet fuel is? Options:
  A) refinery gas
  B) diesel oil
  C) kerosene
  D) gasoline
  Show Answer
  The correct answer is C .
• Question 1849: A hydrocarbon has an empirical formula CH and a vapour density of 39. Determine its molecular formula.[C = 12, H = 1] Options:
  A) C₂H₆
  B) C₃H₈
  C) C₃H₄
  D) C₆H₆
  Show Answer
  The correct answer is D .
• Question 1850:

  If the quantity of oxygen occupying 2.76L container at a pressure of 0.825 atm and 300k is reduced by one-half, what is the pressure exerted by the remaining gas?

  Options:
  A) 1.650atm
  B) 0.825atm
  C) 0.413atm
  D) 0.275atm
  Show Answer
  The correct answer is A .