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Volumetric Analysis

Manganate(VII) titrations

  • 3 things to know
  • Unit A2 2

Overview

Colour change at the end point of a manganate(VII) titration and mole ratio of manganate(VII) to iron(II).

What you need to know

Answer each one before you reveal it.

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Key term

What is the colour change at the end point of a manganate(VII) titration?

Key term

Write the half-equation for the reduction of manganate(VII) in acid.

Key term

Write the half-equation for the oxidation of iron(II).

Questions from this subtopic

Each one with the model answer underneath.

  1. 1

    Why is potassium manganate(VII) described as a self-indicating titrant?

    Model answer

    It is intensely purple and its reduction product is almost colourless, so the first permanent pink tinge marks the end point without any indicator.

  2. 2

    What is the colour change at the end point of a manganate(VII) titration?

    Model answer

    Colourless to the first permanent pale pink.

  3. 3

    Write the half-equation for the reduction of manganate(VII) in acid.

    Model answer

    MnO₄⁻(aq) + 8H⁺(aq) + 5e⁻ → Mn²⁺(aq) + 4H₂O(l).

  4. 4

    Write the half-equation for the oxidation of iron(II).

    Model answer

    Fe²⁺(aq) → Fe³⁺(aq) + e⁻.

  5. 5

    Combine those to give the overall equation.

    Model answer

    MnO₄⁻(aq) + 8H⁺(aq) + 5Fe²⁺(aq) → Mn²⁺(aq) + 4H₂O(l) + 5Fe³⁺(aq).

  6. 6

    What is the mole ratio of manganate(VII) to iron(II)?

    Model answer

    One to five.

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