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: Water can be obtained as the only product during the Options:
  A) combustion of hydrocarbons
  B) neutraliization of an acid by base
  C) combustion of hydrogen
  D) electrolysis of brine
  Show Answer
  The correct answer is C .
• Question 72: The allotropy of carbon used in the decolourization of sugar is Options:
  A) Graphite
  B) Soot
  C) Charcoal
  D) Lampblack
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  The correct answer is C .
• Question 73: Sodium metal is always kept under oil because it Options:
  A) Readily reacts with water
  B) Is reduced by atmospheric nitrogen
  C) Reacts vigorously on exposure to air
  D) Reacts with oxygen and carbon (IV) oxide
  Show Answer
  The correct answer is C .
• Question 74:

  Which of the following statements is correct about the periodic table?

  Options:
  A) Elements in the same period have the same number of valence electrons
  B) The valence electrons of the elements in the same period increase progressively across the period
  C) Elements in the same group have the same number of electron shells
  D) The non-metallic Properties of the elements tend to decrease across each period
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  The correct answer is B .
• Question 75: When ammonia and hydrogen ion bond together to form ammonium ion, the bond formed is called Options:
  A) ionic bond
  B) electrovalent bond
  C) covalent bond
  D) co-ordinate bond
  E) hydrogen bond
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  The correct answer is D .
• Question 76: The ion that will give a white precipitate with aqueous NaOH and soluble in excess of the base is Options:
  A) Ca²⁺
  B) Mg²⁺
  C) Zn²⁺
  D) Cu²⁺
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  The correct answer is C .
• Question 77: When sodium dioxonitrate (lll) (NaNO₂) dissolves in water, ∆H is positive. The process of dissolution is Options:
  A) exothermic
  B) endothermic
  C) isothermal
  D) isomeric
  E) hygroscopic
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  The correct answer is B .
• Question 78:

  Given that M is the mass of a substance deposited during electrolysis and Q is the quantity of electricity consumed, then Faraday's first law can be written as

  [Electrochemical equivalent]

  Options:
  A) M = E/Q
  B) M = EQ
  C) M = Q/E
  D) M = E/2Q
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  The correct answer is B .
• Question 79: The substance least considered as a source of environmental pollution is Options:
  A) Lead compounds
  B) Organophosphorous compounds
  C) Silicate minerals
  D) Uranium
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  The correct answer is C .
• Question 80: In an electrochemical cell, polarization is caused by Options:
  A) Oxygen
  B) Hydrogen
  C) Tetraoxosulphate(IV) acid
  D) Chlorine
  Show Answer
  The correct answer is B .