4.2.2

Displacement Reactions

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Displacement Reactions

A more reactive metal (one that forms positive ions more easily) can remove a less reactive metal from a compound. This is called a displacement reaction.

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Displacement order

  • A metal can only displace another metal from a compound if it is located above it in the reactivity series.
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Example of a displacement reaction

  • Calcium is higher in the reactivity series than copper. This means that calcium is able to displace copper from a copper sulfate solution to create calcium sulfate.
    • Calcium + copper sulfate → calcium sulfate + copper
    • Ca(s) + CuSO4(aq) → CaSO4(aq) + Cu(s)
  • Platinum, on the other hand, is less reactive than copper and so would not be able to displace copper from a copper sulfate solution.

Displacement Reactions - Halogens

More reactive substances can displace (replace) less reactive substances from compounds. For example, chlorine can displace bromine from a compound:

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Displacement reaction

  • Sodium bromide + chlorine → sodium chloride + bromine
    • 2NaBr + Cl2 → 2NaCl + Br2
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Bromide ions (Br-)

  • Bromide ions are oxidised (electrons are lost):
    • 2Br- → Br2 +2e-
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Chlorine (Cl2)

  • Chlorine is reduced (electrons are gained):
    • Cl2 + 2e- → 2Cl-
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Spectator ions

  • The sodium ions are unchanged in the reaction, so we call them spectator ions.

Jump to other topics

1Atomic Structure

2Chemical Bonding

3Quantitative Chemistry

4Chemical Changes

5Energy Changes

6The Rate & Extent of Chemical Change

7Organic Chemistry

8Chemical Analysis

9Chemistry of the Atmosphere

10Using Resources

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