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Transition Metals

Vanadium and chromium chemistry

  • 3 things to know
  • Papers 1 and 3

Overview

The colours of vanadium in its +5, +4, +3 and +2 oxidation states, using E° values to explain reduction by zinc in acid, reducing dichromate(VI) to Cr³⁺ and Cr²⁺ with zinc, oxidising Cr³⁺ with alkaline hydrogen peroxide, and the chromate(VI) and dichromate(VI) equilibrium.

What you need to know

Answer each one before you reveal it.

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Numbers

Write the equilibrium equation for the interconversion between chromate(VI) and dichromate(VI) ions.

Key term

When vanadium is reduced from +5 to +4 using zinc in acidic conditions, why does this reduction occur?

Key term

Explain why zinc in acidic solution can reduce V(III) to V(II).

Questions from this subtopic

Each one with the model answer underneath.

  1. 1

    What colour are vanadium(V) compounds?

    Model answer

    Yellow.

  2. 2

    What colour are vanadium(IV) compounds?

    Model answer

    Blue.

  3. 3

    What colour are vanadium(III) compounds?

    Model answer

    Green.

  4. 4

    What colour are vanadium(II) compounds?

    Model answer

    Violet.

  5. 5

    When vanadium is reduced from +5 to +4 using zinc in acidic conditions, why does this reduction occur?

    Model answer

    The Zn²⁺/Zn couple has a more negative standard electrode potential than the V(V)/V(IV) couple, making the reduction feasible.

  6. 6

    Explain why zinc in acidic solution can reduce V(III) to V(II).

    Model answer

    The Zn²⁺/Zn couple has a more negative standard electrode potential than the V(III)/V(II) couple, making the reduction feasible.

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BIonisation energy removes electrons from the metal atoms.
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