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Redox Reactions

Combining half-equations into a stoichiometric redox equation

  • 3 things to know
  • Component 1

Overview

Mole ratio in which manganate(VII) ions react with iron(II) ions, mole ratio in which dichromate(VI) ions react with iron(II) ions and mole ratio in which iodine reacts with thiosulfate ions.

What you need to know

Answer each one before you reveal it.

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Key term

What must be done to two half-equations before they can be added together?

Key term

Give the overall equation for the reaction between acidified manganate(VII) ions and iron(II) ions.

Key term

State the mole ratio in which manganate(VII) ions react with iron(II) ions.

Questions from this subtopic

Each one with the model answer underneath.

  1. 1

    What must be done to two half-equations before they can be added together?

    Model answer

    Each is multiplied so that the number of electrons lost in the oxidation equals the number gained in the reduction.

  2. 2

    Give the overall equation for the reaction between acidified manganate(VII) ions and iron(II) ions.

    Model answer

    MnO₄⁻ + 5Fe²⁺ + 8H⁺ → Mn²⁺ + 5Fe³⁺ + 4H₂O.

  3. 3

    State the mole ratio in which manganate(VII) ions react with iron(II) ions.

    Model answer

    One mole of MnO₄⁻ reacts with five moles of Fe²⁺.

  4. 4

    Give the overall equation for the reaction between acidified dichromate(VI) ions and iron(II) ions.

    Model answer

    Cr₂O₇²⁻ + 6Fe²⁺ + 14H⁺ → 2Cr³⁺ + 6Fe³⁺ + 7H₂O.

  5. 5

    State the mole ratio in which dichromate(VI) ions react with iron(II) ions.

    Model answer

    One mole of Cr₂O₇²⁻ reacts with six moles of Fe²⁺.

  6. 6

    Give the overall equation for the reaction between acidified manganate(VII) ions and ethanedioate ions.

    Model answer

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

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