IGCSEChemistryCambridge (CIE)Exam Questions6. Chemical ReactionsRedox

Redox (Cambridge (CIE) IGCSE Chemistry): Exam Questions

Exam code: 0620 & 0971

2 hours34 questions

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11 mark

Which row correctly describes oxidation in terms of oxygen, electrons and oxidation state?

 

oxygen is

electrons are

oxidation state is

A

added

added

increased

B

added

lost

increased

C

lost

added

decreased

D

lost

lost

decreased

    Choose your answer

    21 mark

    Magnesium reacts with iron(III) oxide in the following reaction.

    magnesium + iron(III) oxide → magnesium oxide + iron

    Which statement about this reaction is correct?

    • Magnesium oxide is reduced

    • Iron is oxidised

    • Magnesium is oxidised

    • Iron(III) oxide is oxidised

    Choose your answer

    31 mark

    When copper is heated in air, its surface turns black.

    What is happening to the copper in this reaction?

    • Copper undergoes thermal decomposition

    • Copper is oxidised

    • Copper burns with a lilac flame

    • Copper is reduced

    Choose your answer

    41 mark

    Lead(II) oxide undergoes a number of different redox reactions.

    In which of the following reactions is lead(II) oxide, PbO, not reduced?

    • PbO + Zn → Pb + ZnO

    • PbO + H2 → Pb + H2O

    • PbO + C → Pb + CO

    • 2PbO + O2 → 2PbO2

    Choose your answer

    51 mark

    The following equations are all examples of redox reactions.

    In which equation is the underlined substance being oxidised?

    • CO2 + C → 2CO

    • FeO + Mg → MgO + Fe

    • 3CO + Fe2O3 → 2Fe + 3CO2

    • CuCO3 → CuO + CO2

    Choose your answer

    11 mark

    Three reactions are shown below.

    • NO + O3 → NO2 + O2

    • 2C + O2 → 2CO

    • 2MgO + O2 → 2MgO2

    Which row correctly describes the process each reactant molecule undergoes?

     

    NO

    O3

    MgO

    A

    oxidised

    reduced

    oxidised

    B

    oxidised

    oxidised

    reduced

    C

    reduced

    oxidised

    oxidised

    D

    reduced

    reduced

    oxidised

      Choose your answer

      21 mark

      What is the oxidation state of Fe in Fe2O3?

      • +2

      • -2

      • -3

      • +3

      Choose your answer

      31 mark

      Which row correctly describes the process of reduction in terms of oxygen, electrons and oxidation state?

       

      oxygen is

      electrons are

      oxidation state is

      A

      lost

      added

      unchanged

      B

      added

      lost

      increased

      C

      lost

      added

      decreased

      D

      added

      lost

      unchanged

        Choose your answer

        41 mark

        Which row correctly names each compound?

         

        CuSO4

        KMnO4

        FeCl3

        A

        copper sulfate

        potassium manganate (IV)

        iron(II) chloride

        B

        copper sulfate

        potassium manganate (V)

        iron(III) chloride

        C

        copper(II) sulfate

        potassium manganate (VI)

        iron(II) chloride

        D

        copper(II) sulfate

        potassium manganate (VII)

        iron(III) chloride

          Choose your answer

          51 mark

          Potassium iodide is used to test for the presence of oxidising agents.
          Which row correctly describes what happens when potassium iodide is added to an acidified solution containing an oxidising agent?

          • colour change - turns brown
            reason for colour change -iodine is used up

          • colour change - turns brown
            reason for colour change -iodine is formed

          • colour change - turns yellow
            reason for colour change -iodine is used up

          • colour change - no colour change
            reason for colour change -iodine is formed

          Choose your answer

          11 mark

          A series of redox reactions are shown. What is the oxide that undergoes oxidation?

          1

          2CO + 2NO → 2CO2 + N2

          2

          Fe2O3 + 2Al → Al2O3 + 2Fe

          3

          2ZnO + C → 2Zn + CO2

          4

          Fe2O3 + 3CO → 2Fe + 3CO2

          • CO

          • C

          • NO

          • Fe2O3

          Choose your answer

          21 mark

          In which reaction is the reactant being reduced?

          • Mg → Mg2+ + 2ē

          • Mg2+ + 2ē → Mg

          • CrO → Cr2O3

          • C → CO2

          Choose your answer

          31 mark

          Vanadium is a transition element and forms several oxides. In which of the following reactions does vanadium undergo oxidation?

          • V2O3 → VO

          • V2O5 → VO2

          • V2O3 → V2O5

          • VO2 → V2O3

          Choose your answer

          41 mark

          Manganese is a transition element and forms several oxides. In which of the following changes does manganese undergo reduction?

          • Mn2O3 → Mn2O7

          • MnO → MnO3

          • Mn2O2 → MnO

          • MnO → Mn

          Choose your answer

          51 mark

          Potassium manganate (VII) is used to test for the presence of reducing agents. Which row correctly describes what happens when acidified potassium manganate (VII) is added to a solution containing a reducing agent?

          • colour change - pink/purple to colourless
            reason for colour change - MnO4- is oxidised

          • colour change - pink/purple to colourless
            reason for colour change - MnO4- is reduced

          • colour change - colourless to pink/purple
            reason for colour change - MnO4- is oxidised

          • colour change - colourless to pink/purple
            reason for colour change - MnO4- is reduced

          Choose your answer

          61 mark

          Which row correctly describes an oxidising agent and a reducing agent?

          • oxidising agent - adds oxygen to a substance
            reducing agent - removes oxygen from a substance

          • oxidising agent - adds oxygen to a substance
            reducing agent -increases the oxidation number of a substance

          • oxidising agent - removes oxygen from a substance
            reducing agent - adds oxygen to a substance

          • oxidising agent - decreases the oxidation number of a substance
            reducing agent - increases the oxidation number of a substance

          Choose your answer

          71 mark

          Which one of the following substances is commonly used as a reducing agent?

          • H2SO4

          • KMnO4

          • H2O2

          • CO

          Choose your answer

          81 mark

          In which two of the following redox reactions is the substance in bold acting as a reducing agent?

          1

          CuO + H2 → Cu + H2O

          2

          2Ca + O2 → 2CaO

          3

          CO + CuO → Cu + CO2

          4

          CO2 + C → 2CO

          • 1 and 2 only

          • 1 and 3 only

          • 2 and 3 only

          • All of them

          Choose your answer

          91 mark

          Hydrogen and copper(II) oxide react to produce copper metal and water.

          CuO + H2 → Cu + H2O

          Which row correctly describes the oxidising agent and reducing agent?

          • oxidising agent -H2O
            reducing agent -Cu

          • oxidising agent -H2
            reducing agent -CuO

          • oxidising agent -Cu
            reducing agent -H2O

          • oxidising agent -CuO
            reducing agent -H2

          Choose your answer