Reactivity series & displacement reactions
In this topic you will
- use the reactivity series of metals to predict which metals will displace others from a solution of their salts
- carry out some displacement reactions
Key words
- reactivity
- reactivity series
- displacement reaction
The reactivity series
In previous topics, you learnt that some metals are more reactive than others, by looking at the reaction of the metals with oxygen, water (or steam) and dilute acid. Some metals are much more reactive than others. You can use the results of all the investigations, to place the metals in the order of their reactivity.
This list is called the reactivity series. It has the most reactive metals at the top and the least reactive at the bottom.
Common Mistake
Don’t assume that a shiny or expensive-looking metal is always more reactive. For example, gold is one of the least reactive metals even though it's valuable.
This table shows a summary of the reactions of the metals in the reactivity series.
| Metal | Reaction with oxygen | Reaction with water | Reaction with dilute acid |
|---|---|---|---|
| potassium (extension material) |
burns brightly when heated to form an oxide | very vigorous reaction in cold water, the hydroxide is formed | violent reaction and very dangerous |
| sodium (extension material) |
 |
 |
 |
| calcium | burns brightly in air when heated to form an oxide | slow reaction in cold water to form the hydroxide | |
| magnesium |  |
|
reaction, which becomes less vigorous as you go down the list |
| zinc | slow reaction when heated to form an oxide | reacts with steam but not water to form an oxide |
|
| iron |  |
 |
|
| copper | no reaction with steam or water | ||
| silver | no reaction |  |
|
| gold |  |
|
Questions
Show Answer
Lithium should be placed near the top of the reactivity series, just below potassium and sodium, as it is a very reactive alkali metal.
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Lithium reacts quickly with cold water and forms a hydroxide and hydrogen gas, similar to sodium and potassium, indicating its high reactivity.
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Platinum should be placed at the very bottom of the reactivity series, below gold, due to its extremely low reactivity.
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Platinum does not react with air, water, or acids under normal conditions, and remains untarnished, showing it is less reactive than gold.
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The most reactive metal is the one producing the most bubbles of gas (hydrogen). Greater bubbling indicates a faster reaction and higher reactivity.
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zinc + sulfuric acid → zinc sulfate + hydrogen
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magnesium + oxygen → magnesium oxide
Displacement reactions
If you place a clean iron nail in a beaker containing copper sulfate solution, there is an interesting reaction.
The blue copper sulfate solution changes to a slightly paler colour. The most remarkable thing that happens is that the nail looks a different colour. It has become copper coloured. What has happened in this reaction?
The word and symbol equations for this reaction are:
copper sulfate + iron → iron sulfate + copper
CuSO₄ + Fe → FeSO₄ + Cu
The iron nail has become coated with copper. Iron is more reactive than the copper that it has ‘pushed out’ from the copper sulfate and has reacted to form iron sulfate. This ‘pushing out’ is called displacement, so this type of reaction is called a displacement reaction. A more reactive metal can replace a less reactive one in a salt.
If a copper nail was placed in a solution of iron sulfate there would be no reaction because copper is less reactive than iron. Copper cannot displace the iron in the iron sulfate.
Quick Fact
Displacement reactions are often used in metal extraction and corrosion prevention. They are key to understanding how reactive metals behave in real-world applications.
Questions
Use the reactivity series to answer these questions.
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Zinc is more reactive than copper.
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Yes, zinc can displace copper from copper sulfate because zinc is more reactive.
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Magnesium is more reactive than silver.
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No, silver cannot displace magnesium because it is less reactive.
Think Like a Scientist
This investigation explores how different metals displace one another from salt solutions. The experiment helps you understand the reactivity series by comparing which metals can displace others.
Equipment: copper sulfate, magnesium sulfate, iron sulfate and zinc sulfate solutions; small pieces of iron, zinc, copper, and magnesium; test tubes, test tube rack, forceps, safety glasses.
Method:
Step 1: Read through the instructions and prepare a results table.
Step 2: Pour copper sulfate solution into three test tubes, each one-third full.
Step 3: Add a small piece of iron to one, magnesium to the second, and zinc to the third.
Step 4: Wait a few minutes.
Step 5: Observe and record any changes.
Step 6: Repeat Steps 2–5 using magnesium sulfate solution with copper, iron and zinc.
Step 7: Repeat Steps 2–5 using iron sulfate solution with copper, magnesium and zinc.
Step 8: Repeat Steps 2–5 using zinc sulfate solution with copper, iron and magnesium.
Show Answer
You know a metal has displaced another when a solid metal appears and the solution changes color. This means the more reactive metal has replaced the less reactive one from the solution.
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Magnesium is the most reactive metal because it displaces the other three metals from their salt solutions.
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Copper is the least reactive metal because it does not displace any of the others from their solutions.