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 151: Elements in the same period in the periodic table have the same Options:
  A) number of shells
  B) atomic number
  C) chemical properties
  D) physical properties
  Show Answer
  The correct answer is A .
• Question 152: In recharging a lead-acid accumulator, the reaction at the cathode can be represented as Options:
  A) Pb²⁺_(aq) + SO^2-_4(aq) →PbSO_4(s)
  B) Pb²⁺_(aq) + 2e^- →Pb_(s)
  C) Pb²⁺_(aq) + 2H₂O_(l) → PbO_2(s) + 4H⁺_(aq) + 4e^-
  D) Pb_(s) → Pb²⁺_(aq) + 2e^-
  Show Answer
  The correct answer is D .
• Question 153: Under high pressure, real gases do not obey gas laws because their molecules? Options:
  A) have become more energetic
  B) have become less energetic
  C) have become smaller in size
  D) decompose into atoms
  E) start repelling each other
  Show Answer
  The correct answer is B .
• Question 154:

  0.46g of ethanol when burned raised the temperature of 50g of water by 14.3K. Calculate the heat of combustion of ethanol.

  [C = 12, O = 16, H = 1, Specific heat capacity of water = 4.2 jg^-1K^-1]

  Options:
  A) +3000 KJ mol^-1
  B) +300 KJ mol^-1
  C) -300 KJ mol^-1
  D) -3000 KJ mol^-1
  Show Answer
  The correct answer is C .
• Question 155: The number of hydrogen ions in 4.9 g of tetraoxosulphate (IV) acid is?(S = 32, O =16, H = 1, Na = 6.02 x 10₂₃ Options:
  A) 3.01 x 10₂₂
  B) 6.02 x 10₂₂
  C) 3.01 x 10₂₃
  D) 6.01 x 10₂₃
  Show Answer
  The correct answer is B .
• Question 156: Calculate the volume of carbon (IV)oxide measured at s.t.p, produced when 1 kg of potassium hydrogen trioxocarbonate (IV) is totally decomposed by heat?(G.M.V. at s.t.p 22.4 dm³, K = 39, O = 16, C = 12, H = 1) Options:
  A) 28 dm³
  B) 56 dm³
  C) 112 dm³
  D) 196 dm³
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  The correct answer is C .
• Question 157: When few drops of concentrated trioxonitrate(V) acid is added to an unknown sample and wanned an intense yellow colouration is observed. The likely functional group present in the sample is Options:
  A) NH₃—C—C=O
  B) CHO
  C) CO
  D) CNH₂
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  The correct answer is A .
• Question 158: The ores that can be concentrated by flotation are Options:
  A) nitride ores
  B) sulphide ores
  C) oxide ores
  D) non-metals
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  The correct answer is B .
• Question 159:

  An element X has two isotopes, ²⁰₁₀X and ²⁰₁₀X, present in the ratio 1:3. The relative atomic mass of X would be?

  Options:
  A) 20.5
  B) 21.0
  C) 21.5
  D) 22.0
  E) 22.5
  Show Answer
  The correct answer is C .
• Question 160: A liquid that will dissolve fat is Options:
  A) hydrochloric acid
  B) calcium hydrochloride
  C) kerosene
  D) water
  Show Answer
  The correct answer is C .