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 21: The conversion of open chain alkanes into cycloalkanes and aromatic compounds is called Options:
  A) cracking
  B) reforming
  C) isomerization
  D) polymerization
  Show Answer
  The correct answer is B .
• Question 22: 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 23: When pollen grains are suspended in water and viewed through a microscope, they appear to be in a state of constant but erratic motion. This is due to? Options:
  A) convection currents
  B) small changes
  C) small changes in temperature
  D) a chemical reaction between the pollen grain and water
  E) the bombardment of the pollen grains by molecules of water
  Show Answer
  The correct answer is E .
• Question 24: Deliquescent substance are used for Options:
  A) Cooling
  B) Wetting
  C) Melting
  D) Drying
  Show Answer
  The correct answer is D .
• Question 25: Ethanol reacts with concentrated tetraoxosulphate (V) acid at a temperature above 170 ^oC to form Options:
  A) ethanone
  B) ethene
  C) ethyne
  D) ethanal
  Show Answer
  The correct answer is B .
• Question 26: Elements X and Y have electronic configurations 1s²2s²2p⁶ and 1s²2s²2p⁶3s²3p¹ respectively. When they combine, the formula of the compound formed is Options:
  A) XY
  B) YX
  C) X₂Y₃
  D) Y₂X₃
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  The correct answer is D .
• Question 27:

  When chlorine water is exposed to bright sunlight, the following products are formed

  Options:
  A) HCl${}_{(aq)}$ and Cl${}_2$
  B) HOCl${}_{(aq)}$ and Cl${}_2$
  C) HCl${}_{(aq)}$ and O${}_2$
  D) HOCl${}_{(aq)}$ and O${}_2$
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  The correct answer is C .
• Question 28:

  Elements in the periodic table are arranged in the order of their

  Options:
  A) atomic numbers
  B) metallic character
  C) mass number
  D) relative atomic mass
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  The correct answer is A .
• Question 29: Tin is unaffected by air at ordinary temperature due to its Options:
  A) Low melting point
  B) Weak electropositive character
  C) High boiling point
  D) White lustrous appearance
  Show Answer
  The correct answer is A .
• Question 30: The iron (III) oxide impurity in bauxite can be removed by? Options:
  A) Fractional crystallization in acid solution
  B) dissolution in sodium hydroxide and filtration
  C) extraction with concentrated ammonia and reprecipitation
  D) electroysis of molten mixture
  Show Answer
  The correct answer is B .