Displacement reactions
A displacement reaction happens when a more reactive element takes the place of a less reactive element in a compound. For metals in solution, compare the added metal with the metal in the dissolved compound.
Put metals in order with Reactivity Rank.
How to predict a displacement reaction
Compare the added metal with the metal in the solution using the reactivity series. If the added metal is more reactive, it can take the other metal’s place. If it is less reactive, or the same metal, there is no displacement.
The picker uses magnesium, zinc, iron and copper with their sulfate solutions. It predicts the products for these pairs. Iron sulfate here means iron(II) sulfate.
Displacement reaction examples
Zinc is more reactive than copper. Add zinc to copper sulfate solution and zinc sulfate and copper form: zinc + copper sulfate → zinc sulfate + copper. The blue solution becomes paler as copper ions are removed, and copper forms on the zinc.
Copper is less reactive than zinc. Copper added to zinc sulfate solution cannot displace zinc, so there is no displacement reaction. Magnesium can displace iron from iron(II) sulfate: magnesium + iron(II) sulfate → magnesium sulfate + iron.
In symbols, the zinc example is Zn + CuSO₄ → ZnSO₄ + Cu. The page on balancing equations explains how to check the number of atoms on each side.
Electrons in displacement
In the zinc and copper example, zinc atoms lose electrons to form zinc ions. Copper ions gain those electrons to form copper atoms. Loss of electrons is oxidation and gain is reduction. Both happen in this reaction, so it is a redox reaction. Explaining redox in terms of electron transfer is Higher tier on AQA, Edexcel and OCR Gateway.
The ionic equation for this example is Zn(s) + Cu²⁺(aq) → Zn²⁺(aq) + Cu(s). The sulfate ions do not change and are left out. Writing ionic equations is Higher tier for AQA, Edexcel and OCR Gateway.
Other reactions
Displacement is one way substances react. In neutralisation, an acid reacts with a base to make a salt and water. The chemistry hub links to more guides and games.
Common mistakes
- Reversing the order: the added metal must be more reactive than the metal in the compound.
- Predicting displacement when the added metal and the metal in solution are the same.
- Adding sulfate ions to the ionic equation when they do not change.
Try another way to explore ions with ionic bonding.
Questions people ask
What is a displacement reaction?
It is a reaction in which a more reactive element takes the place of a less reactive element in a compound.
Can copper displace zinc from zinc sulfate?
No. Copper is less reactive than zinc, so it cannot displace zinc from zinc sulfate solution.
What happens when zinc is added to copper sulfate?
Zinc displaces copper. Zinc sulfate and copper form.
Does a metal displace itself from a solution?
No. A metal cannot displace the same metal from its compound.