Displacement reactions of solutions

A more reactive metal will displace a less reactive metal from a solution of one of its salts. For example:

magnesium + copper(II) sulfate → copper + magnesium sulfate

Mg(s) + CuSO4(aq) → Cu(s) + MgSO4(aq)

In this reaction, the blue colour of the copper(II) sulfate fades as it is used up (magnesium sulfate solution is colourless). We would also see copper metal (red/brown solid) forming.

Diagram showing that when magnesium and blue copper(II) sulfate solution are stirred, it forms a colourless magnesium sulfate solution and copper.

Reactions between metals and solutions of metal salts allow us to put a selection of metals into a reactivity series. Using metals J, K and L:

Metal JMetal KMetal L
J sulfateXNo reaction observedNo reaction observed
K sulfateDisplaces KXDisplaces K
L sulfateDisplaces LNo reaction observedX

Note that the displacement is observed by a change in colour of the metal and/or a change in colour of the solution.

  • Metal J displaces both K and L – so it must be the most reactive and be at the top of this reactivity series.
  • Metal K cannot displace either J or L – so it must be the least reactive and be at the bottom of this reactivity series.
  • Metal L displaces K but cannot displace J – so it must be more reactive than K but less reactive than J, and be in between them in this reactivity series.

Therefore, the order is:

Three boxes positioned vertically labelled J, L and K. An arrow pointing upwards is labelled Increasing reactivity.
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