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Friday, 22 May 2026
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Chemistry Past Questions and Answers

Jamb 1992 Chemistry Questions

Question 21:
Copper (II) tetraoxosulphate (VI) solution is electrolyzed using carbon electrodes. Which of the following are produced at the anode and cathode respectively ?
  • A Copper and oxygen
  • B Oxygen and copper
  • C Hydrogen and copper
  • D Copper and hydrogen
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Question 22:
Calculate the mass, in kilograms, of magnesium produced by the electrolysis of magnesium (II) chloride in a cell operating for 24 hours at 500 amperes.
  • A 2.7
  • B 5.4
  • C 10.8
  • D 21.7
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Question 23:
S2O2-3 + I2 → S2O62- + 2I-. In reaction above, the oxidizing agent is?
  • A S<sub style='font-size: smaller;'>2</sub>O<sub style='font-size: smaller;'>3</sub><sup style='font-size: smaller;'>2-</sup>
  • B I<sub style='font-size: smaller;'>2</sub>
  • C S<sub style='font-size: smaller;'>4</sub>O<sub style='font-size: smaller;'>6</sub><sup style='font-size: smaller;'>2-</sup>
  • D I<sup style='font-size: smaller;'>-</sup>
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Question 24:
MnO2 + 2CI- + 4H+ → MnO2+ + CI2 + 2H2O.
The changes is oxidation numbers when the manganese, chloride and hydrogen ions react according to the above equation are respectively?
  • A 2, 2, 4
  • B -1, -2, 4
  • C -2, 1, 0
  • D 2, 4, 0
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Question 25:
In which of the following is the entropy change positive?
  • A H<sub style='font-size: smaller;'>2</sub>O<sub style='font-size: smaller;'>(I)</sub> → H<sub style='font-size: smaller;'>2</sub>O<sub style='font-size: smaller;'>(g)</sub>
  • B Cu<sup style='font-size: smaller;'>2+</sup><sub style='font-size: smaller;'>(aq) + Fe(s)</sub> → Fe<sup style='font-size: smaller;'>(2+)</sup> + Cu<sub style='font-size: smaller;'>(s)</sub>
  • C N<sub style='font-size: smaller;'>2</sub><sub style='font-size: smaller;'>(g)</sub> + 3H<sub style='font-size: smaller;'>2</sub><sub style='font-size: smaller;'>(g)</sub> → 2NH<sub style='font-size: smaller;'>3</sub><sub style='font-size: smaller;'>(g)</sub>
  • D 2HCI<sub style='font-size: smaller;'>(s)</sub> → H<sub style='font-size: smaller;'>2</sub><sub style='font-size: smaller;'>(g)</sub> + CI<sub style='font-size: smaller;'>2</sub><sub style='font-size: smaller;'>(g)</sub>
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