Chemistry 2018 Past Questions | WAEC

Study the following Chemistry past questions and answers for JAMBWAEC  NECO and Post-JAMB. Get prepared with official past questions and answers for upcoming examinations.

21The number of Hydrogen ions in 1.0dm3dm3 of 0.02moldm3moldm−3 tetraoxosulphate(VI) acid is   [NA=6.02×1023][NA=6.02×1023]

  • A. 1.2×10221.2×1022
  • B. 1.2×10231.2×1023
  • C. 2.4×10222.4×1022
  • D. 2.4×1023

22.  The most suitable substance for putting out petrol fire is

  • A. water
  • B. carbon(IV) oxide
  • C. fire blanket
  • D. sand

23. The following factors would contribute to environmental pollution except

  • A. production of ammonia
  • B. manufacture of cement
  • C. photosynthesis
  • D. combustion

24.  The position of equilibrium in a reversible reaction is affected by

  • A. particle size of the reactants
  • B. vigorous stirring of the reaction mixture
  • C. presence of a catalyst
  • D. change in concentration of the reactants

25. Id9V4BbdPBcKvLfqVVLRovefRrMdqb9ePs4vvkX8

The diagram above illustrates a conical flask containing water and ice. Which of the following is correct about the diagram?

  • A. The water is at lower temperature than the ice
  • B. Energy is absorbed when the ice changes to water
  • C. Energy is released when the ice changes to water
  • D. The water molecules vibrate about a fixed point

26.  Which of the following statements best explains the difference between a gas and a vapour?

  • A. Unlike gases, vapours are liquids at room temperature
  • B. Unlike gases, vapour can easily be condensed into liquids
  • C. Unlike gases, vapour is readily converted into solids
  • D. Vapours are generally denser than gases

27.  Consider the following reaction equation: 2HCl+Ca(OH)2CaCl2+H2O2HCl+Ca(OH)2→CaCl2+H2O. What is the volume of 0.1moldm3moldm−3 HCl that would completely neutralize 25cm3cm3 of 0.3moldm3moldm−3 Ca(OH)22?

  • A. 150cm3cm3
  • B. 75cm3cm3
  • C. 30cm3cm3
  • D. 25cm3


CuCu and HNO3HNO3 are not suitable for preparing hydrogen gas because of their

  • A. reactivity and oxidation respectively
  • B. conductivity and corrosiveness respectively
  • C. melting point and reduction respectively
  • D. electronegativity and solubility respectively

29. Which of the following CANNOT be an empirical formula?

  • A. CHCH
  • B. CH2CH2
  • C. P2O5P2O5
  • D. N2O4

30.  One of the criteria for confirming the purity of benzene is to determine its

  • A. heat capacity
  • B. boiling point
  • C. mass
  • D. colour

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