WAEC Chemistry questions: Oxidation and reduction

19 questions with answers and explanations. Tap an option to check yourself.

1. Question 1· Oxidation and reduction· WAEC

   In the reaction Fe₂O₃ + 3CO → 2Fe + 3CO₂, the substance that is reduced is

   • ACO
   • BFe₂O₃
   • CFe
   • DCO₂

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2. Question 2· Oxidation and reduction· WAEC

   Find the oxidation number of nitrogen in NO₂.

   • A−4
   • B+2
   • C+4
   • D+6

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3. Question 3· Oxidation and reduction· WAEC

   In terms of electrons, oxidation is

   • Aloss of neutrons
   • Bgain of electrons
   • Cgain of protons
   • Dloss of electrons

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4. Question 4· Oxidation and reduction· WAEC

   Which of these is an oxidising agent?

   • Ahydrogen gas
   • Bhydrogen sulphide
   • Ccarbon(II) oxide
   • Dacidified potassium heptaoxodichromate(VI)

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5. Question 5· Oxidation and reduction· WAEC

   Acidified potassium dichromate(VI) turns from orange to green when it

   • Ais neutralised
   • Bis oxidised
   • Cis reduced
   • Dis heated alone

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6. Question 6· Oxidation and reduction· WAEC

   In the reaction CuO + H₂ → Cu + H₂O, copper(II) oxide is

   • Aa catalyst
   • Boxidised
   • Creduced
   • Dneutralised

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7. Question 7· Oxidation and reduction· WAEC

   The oxidation number of chromium in K₂Cr₂O₇ is

   • A+3
   • B+7
   • C+6
   • D+12

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8. Question 8· Oxidation and reduction· WAEC

   The oxidation number of sulphur in H₂SO₄ is

   • A+6
   • B+4
   • C−2
   • D+2

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9. Question 9· Oxidation and reduction· WAEC

   Which of these is a redox reaction?

   • ACaCO₃ → CaO + CO₂
   • BNaOH + HCl → NaCl + H₂O
   • CAgNO₃ + NaCl → AgCl + NaNO₃
   • DZn + CuSO₄ → ZnSO₄ + Cu

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10. Question 10· Oxidation and reduction· WAEC

    What is the oxidation number of chromium in potassium heptaoxodichromate(VI), K₂Cr₂O₇?

    • A+3
    • B+7
    • C+6
    • D+12

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11. Question 11· Oxidation and reduction· WAEC

    In the change Fe²⁺ → Fe³⁺ + e⁻, the iron(II) ion is

    • Areduced
    • Boxidised
    • Cneutralised
    • Dhydrolysed

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12. Question 12· Oxidation and reduction· WAEC

    Find the oxidation number of manganese in KMnO₄.

    • A+4
    • B+7
    • C+6
    • D−7

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13. Question 13· Oxidation and reduction· WAEC

    Hydrogen sulphide gas is a good

    • Acatalyst
    • Boxidising agent
    • Cdrying agent
    • Dreducing agent

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14. Question 14· Oxidation and reduction· WAEC

    The oxidation number of nitrogen in NH₃ is

    • A+3
    • B−3
    • C0
    • D+5

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15. Question 15· Oxidation and reduction· WAEC

    In terms of electron transfer, oxidation is the

    • Again of electrons
    • Bloss of electrons
    • Cgain of protons
    • Dloss of neutrons

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16. Question 16· Oxidation and reduction· WAEC

    Oxidation in terms of oxidation number is

    • Ano change in oxidation number
    • Ba decrease in oxidation number
    • Can increase in oxidation number
    • Dthe gain of electrons

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17. Question 17· Oxidation and reduction· WAEC

    An oxidising agent

    • Agains electrons
    • Bloses electrons
    • Cgains protons
    • Ddonates hydrogen

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18. Question 18· Oxidation and reduction· WAEC

    Zinc dust added to blue copper(II) tetraoxosulphate(VI) solution reacts as Zn + Cu²⁺ → Zn²⁺ + Cu. Which species is reduced?

    • Athe copper(II) ion
    • Bzinc metal
    • Cthe zinc ion
    • Dcopper metal

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19. Question 19· Oxidation and reduction· WAEC

    In the reaction 2Mg + O₂ → 2MgO, the reducing agent is

    • Amagnesium
    • Boxygen
    • Cmagnesium oxide
    • Dnone

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    Explanation and discussion