Transition Metal Reactions (Edexcel International A Level Chemistry)

Exam Questions

11 mark

Aqueous ammonia is added drop by drop to a solution of cobalt(II) chloride, CoCl2(aq), until in excess.

What would be the sequence of observations?

  • blue solution → pink precipitate → dark blue solution

  • pink solution → blue precipitate

  • blue solution → pink precipitate

  • pink solution → blue precipitate → yellow‐brown solution

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11 mark

When an alkene is added to a solution of potassium manganate(VII), the purple solution turns colourless.

In terms of electron transfer and oxidation number, how does the manganese change in this reaction?

      Electron transfer Oxidation number
  A gains electrons increases
  B gains electrons decreases
  C loses electrons increases
  D loses electrons decreases

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    21 mark

    Aqueous sodium hydroxide was added to aqueous iron(II) sulfate and the mixture allowed to stand.

    What would be observed?

        Observations
        Immediately after adding
    sodium hydroxide
    After standing
    A brown precipitate no change
    B green precipitate no change
    C brown precipitate precipitate turns green
    D green precipitate precipitate turns brown 

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      31 mark

      Which of the following is not true of the reactions occurring in the catalytic converter fitted to a car exhaust?

      • they involve heterogeneous catalysis

      • carbon monoxide is adsorbed onto the surface of the catalyst

      • nitrogen is desorbed from the surface of the catalyst

      • the products cause no harm to the environment

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      41 mark

      When aqueous ammonia is added to an aqueous solution of zinc sulfate, a white precipitate forms which dissolves in excess ammonia to give a colourless solution.

      What types of reaction are occurring?

          Type of reaction
          Formation of white
      precipitate
      Formation of colourless
      solution
      A deprotonation ligand exchange
      B deprotonation deprotonation
      C ligand exchange deprotonation
      D ligand exchange ligand exchange

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        51 mark

        The reaction of ethanedioate ions, C2O42–, with manganate(VII) ions, MnO4, in acidic solution involves autocatalysis.

        2MnO4 + 16H++ 5C2O42– → 2Mn2+ + 10CO2 + 8H2O

        The catalyst in this reaction is

        • Mnstraight O subscript 4 superscript minus

        • H+

        • Mn2+

        • CO2

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        61 mark

        Iodide ions are oxidised by peroxodisulfate ions in aqueous solution.

        2 straight I to the power of minus space plus space straight S subscript 2 straight O subscript 8 superscript 2 minus end superscript space rightwards arrow space straight I subscript 2 space plus space 2 SO subscript 4 superscript 2 minus end superscript

        This reaction is catalysed by adding Fe2+ ions to the solution.
        This catalysis is effective because

        • Fe2+ reacts with iodide ions and with peroxodisulfate ions

        • Fe2+ has many electrons in its outermost subshells

        • Fe2+ has many active sites on which the reaction can occur

        • Fe2+ is readily oxidised to Fe3+ which is then reduced to Fe2+

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        11 mark

        Iodide ions, I, are oxidised by peroxodisulfate(VI) ions, S2straight O subscript 8 superscript 2 minus end superscript.

        2I(aq) + S2straight O subscript 8 superscript 2 minus end superscript(aq) → I2(aq) + 2Sbegin mathsize 16px style O subscript 4 to the power of 2 minus sign end style(aq)

        Which of the following statements is true of this reaction?

        • both Fe2+(aq) and Fe3+(aq) catalyse the reaction

        • Fe2+(aq) catalyses the reaction but Fe3+(aq) does not

        • Fe3+(aq) catalyses the reaction but Fe2+(aq) does not

        • neither Fe2+(aq) nor Fe3+(aq) catalyses the reaction

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