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Thursday, 11 June 2026
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Chemistry Past Questions and Answers

Chemistry Questions

Question 2621:
WAEC 2000
In which of the following is the oxidation number of sulphur equal to -2?
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  • A S<sub style='font-size: smaller;'>8</sub>
  • B H<sub style='font-size: smaller;'>2</sub>S
  • C SO <sub style='font-size: smaller;'>2</sub>
  • D SO <sub style='font-size: smaller;'>3</sub><sup style='font-size: smaller;'>2-</sup>
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Question 2622:
WAEC 2000
An iron nail placed in a solution copper (ll) tetraoxosulphate (VI) is soon covered with a deposit of copper which of the following equations represents the reactions ?
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  • A Fe <sup style='font-size: smaller;'>2+</sup><sub style='font-size: smaller;'>(aq)</sub> + Cu<sub style='font-size: smaller;'>(s)</sub> → Fe <sup style='font-size: smaller;'>3+</sup> + Cu <sup style='font-size: smaller;'>2+</sup><sub style='font-size: smaller;'>(aq)</sub>
  • B Fe <sup style='font-size: smaller;'>2+</sup><sub style='font-size: smaller;'>(aq)</sub> + Cu<sub style='font-size: smaller;'>(s)</sub> → Fe<sub style='font-size: smaller;'>(s)</sub> + Cu<sup style='font-size: smaller;'>2+</sup><sub style='font-size: smaller;'>(aq)</sub>
  • C Fe <sub style='font-size: smaller;'>(s)</sub> + Cu<sup style='font-size: smaller;'>2+</sup><sub style='font-size: smaller;'>(aq)</sub> → Fe<sup style='font-size: smaller;'>2+</sup><sub style='font-size: smaller;'>(aq)</sub> + Cu<sup style='font-size: smaller;'>2+</sup><sub style='font-size: smaller;'>(aq)</sub>
  • D Fe<sub style='font-size: smaller;'>(s)</sub> + Cu<sup style='font-size: smaller;'>2+</sup> → Fe<sup style='font-size: smaller;'>2+</sup><sub style='font-size: smaller;'>(aq)</sub> + Cu<sub style='font-size: smaller;'>(s)</sub>
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Question 2623:
WAEC 2000
0.10 mol dm<sup style='font-size: smaller;'>-3</sup> NaCI conducts electricity better than 0.10 mol dm<sup style='font-size: smaller;'>-3</sup> CH<sub style='font-size: smaller;'>3</sub>COOH because the solution of NaCI
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  • A Contains more ions
  • B Is neutral to litmus
  • C Has a lower molar mass
  • D Has a higher pH
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Question 2624:
WAEC 2000
Which of the following occurs when a solution of CuSO<sub style='font-size: smaller;'>4</sub>/> is electrolysed using copper electrodes?
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  • A The cathode becomes coated with copper
  • B Both electrodes gain electrons
  • C The blue colour of the solution fades gradually
  • D The anode increases in mass
View Answer & Explanation
Question 2625:
WAEC 2000
Which of the following procedures is suitable for identifying the food colouring added to a pastry sample?
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  • A The cathode becomes coated with copper
  • B Both electrodes gain electrons
  • C The blue colour of the solution fades gradually
  • D The anode increases in mass
View Answer & Explanation

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