Displacement reactions of solutions
A more reactive metal will Take the place of another substance in a chemical reaction. For example, a metal can displace a less reactive metal from its oxide, removing oxide ions from the less reactive metal and becoming an oxide itself. 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.
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 J | Metal K | Metal L | |
| J sulfate | X | No reaction observed | No reaction observed |
| K sulfate | Displaces K | X | Displaces K |
| L sulfate | Displaces L | No reaction observed | X |
| J sulfate | |
|---|---|
| Metal J | X |
| Metal K | No reaction observed |
| Metal L | No reaction observed |
| K sulfate | |
|---|---|
| Metal J | Displaces K |
| Metal K | X |
| Metal L | Displaces K |
| L sulfate | |
|---|---|
| Metal J | Displaces L |
| Metal K | No reaction observed |
| Metal L | X |
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:
