Displacement reactions of metal oxides
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 A substance formed by the chemical union of two or more elements.. The A displacement or competition reaction between aluminium and iron oxide, producing aluminium oxide and iron. It releases enough heat to melt the iron, so it can be used for joining railway tracks together. is a good example of this. It is used to produce white hot molten (liquid) iron in remote locations for welding. A lot of heat is needed to start the reaction (a magnesium fuse is used, which provides heat to the reactants), but then it releases an incredible amount of heat, enough to melt the iron.
aluminium + iron(III) oxide 鈫 iron + aluminium oxide
2Al + Fe2O3 鈫 2Fe + Al2O3
As aluminium is more reactive than iron, it displaces iron from iron(III) oxide. The aluminium removes oxygen from the iron(III) oxide:
- iron(III) oxide is The loss of oxygen, gain of electrons, or gain of hydrogen by a substance during a chemical reaction.
- aluminium is The gain of oxygen, or loss of electrons, by a substance during a chemical reaction.
Reactions between metals and metal oxides allow us to put a selection of metals into a reactivity series. Using metals A, B and C:
| Metal A | Metal B | Metal C | |
| A oxide | X | Displaces A | Displaces A |
| B oxide | No reaction | X | No reaction |
| C oxide | No reaction | Displaces C | X |
| A oxide | |
|---|---|
| Metal A | X |
| Metal B | Displaces A |
| Metal C | Displaces A |
| B oxide | |
|---|---|
| Metal A | No reaction |
| Metal B | X |
| Metal C | No reaction |
| C oxide | |
|---|---|
| Metal A | No reaction |
| Metal B | Displaces C |
| Metal C | X |
- Metal A cannot displace either B or C 鈥 so it must be the least reactive and be at the bottom of this reactivity series.
- Metal B displaces both A and C 鈥 so it must be the most reactive and be at the top of this reactivity series.
- Metal C displaces A but cannot displace B 鈥 so it must be more reactive than A but less reactive than B, and be in between them in this reactivity series.
Therefore, the order is:
In general, the greater the difference in reactivity between two metals in a displacement reaction, the greater the amount of energy released.
Aluminium is much higher than iron in the reactivity series, so the thermite reaction releases a lot of energy. Magnesium is very high in the reactivity series, and copper is very low 鈥 so the reaction between magnesium and copper(II) oxide is more violent.