JAMB and WAEC Chemistry questions: Oxidation and reduction

41 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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   Explanation and discussion

2. Question 2· Oxidation and reduction· JAMB

   Which change is a reduction?

   • ANa → Na⁺
   • BFe²⁺ → Fe³⁺
   • CCl⁻ → Cl₂
   • DFe³⁺ → Fe²⁺

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3. Question 3· Oxidation and reduction· WAEC

   Find the oxidation number of nitrogen in NO₂.

   • A−4
   • B+2
   • C+4
   • D+6

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4. Question 4· Oxidation and reduction· JAMB

   In terms of electron transfer, oxidation is

   • Athe loss of electrons
   • Bthe gain of electrons
   • Cthe gain of hydrogen
   • Dthe loss of oxygen

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5. Question 5· Oxidation and reduction· JAMB

   Find the oxidation number of chromium in K₂Cr₂O₇.

   • A+7
   • B+6
   • C+3
   • D+12

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6. Question 6· 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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7. Question 7· 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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8. Question 8· 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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9. Question 9· Oxidation and reduction· JAMB

   A metal high in the electrochemical series

   • Acannot lose electrons
   • Bis less reactive
   • Cdisplaces metals below it from solutions of their salts
   • Dis a noble metal

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10. Question 10· Oxidation and reduction· JAMB

    In the reaction 2FeCl₂ + Cl₂ → 2FeCl₃, the oxidising agent is

    • AFeCl₃
    • BFeCl₂
    • CCl₂
    • DFe

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11. Question 11· Oxidation and reduction· WAEC

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

    • Aa catalyst
    • Boxidised
    • Creduced
    • Dneutralised

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12. Question 12· Oxidation and reduction· WAEC

    The oxidation number of chromium in K₂Cr₂O₇ is

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

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13. Question 13· Oxidation and reduction· WAEC

    The oxidation number of sulphur in H₂SO₄ is

    • A+6
    • B+4
    • C−2
    • D+2

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14. Question 14· Oxidation and reduction· JAMB

    In the reaction Cl₂ + 2NaOH → NaCl + NaOCl + H₂O, chlorine is

    • Aonly reduced
    • Bonly oxidised
    • Cboth oxidised and reduced
    • Dneither oxidised nor reduced

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15. Question 15· 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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16. Question 16· 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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17. Question 17· Oxidation and reduction· JAMB

    The oxidation number of manganese in KMnO₄ is:

    • A+2
    • B+4
    • C+6
    • D+7

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18. Question 18· Oxidation and reduction· JAMB

    Find the oxidation number of chlorine in NaClO₃.

    • A−1
    • B+3
    • C+7
    • D+5

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19. Question 19· Oxidation and reduction· WAEC

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

    • Areduced
    • Boxidised
    • Cneutralised
    • Dhydrolysed

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20. Question 20· Oxidation and reduction· WAEC

    Find the oxidation number of manganese in KMnO₄.

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

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    Explanation and discussion