Displacement Reaction: Definition, Equation, Types, & Applications

Have you ever mixed two chemicals and seen one push the other out to form something new? That’s exactly what happens in a displacement reaction. This type of reaction is not only interesting to observe but also plays a key role in many chemical processes around us from extracting metals to purifying water. In this article, we’ll break down what displacement reactions are, how they work, the types you need to know for your exams, and some real life applications. So, if you’re preparing for NEET, JEE, or just brushing up for your school test, you are in the right place. Let’s scroll down and understand displacement reactions in the simplest way possible.

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Displacement Reaction

It is a chemical reaction in which a more reactive element takes the place of the less reactive element. This type of reaction includes both metals and non-metals. It is also known as replacement or exchange reaction.

E.g., Magnesium is a more reactive element than copper. When we put magnesium into the blue copper sulphate solution, there occurs a displacement reaction. The more reactive magnesium displaces the copper and yields copper and magnesium sulphate. This reaction can be written as:

The displacement reactions are represented by the following general formula:

A + B-C → A-C + B

Where, If A and B are halogens, C will be a cation And if A and B are metals, C will be anion

Displacement Reaction Diagram

Take a test tube. Fill it with blue copper sulphate solution. Now drop the iron nail in it. After some time, the displacement reaction will occur. The layer of copper metal will cover the iron nail, and its colour will change into red-brown. The blue copper sulphate solution will transform into the light green solution of iron sulphate.

Types of Displacement Reaction

There are two types of displacement reactions.

Single Displacement Reaction:

It is a replacement reaction in which a single ion or element displaces another ion or element from its compound. These types of reactions are also known as single replacement reactions.

E.g., if we take a zinc strip and dip it into the solution of blue copper sulphate, copper metal will be replaced by zinc. The colour of the solution will also disappear.

Double Displacement Reaction

It is that type of replacement reaction in which two elements change their position with each other. It is also known as a double replacement reaction and can be represented by the following general formula:

AB + CD → CB + AD

In the above formula, the two elements ‘A’ and ‘C’ replace their positions with each other.

E.g., When we combine the sodium sulphate solution and barium chloride solution, the result is white precipitation of barium sulphate. It can be shown as:

Examples of Displacement Reaction

Category	Example	Explanation in Simple Words
In the Lab	Zn + CuSO₄ → ZnSO₄ + Cu	Zinc replaces copper from copper sulphate solution. Copper gets deposited and zinc forms a salt.
	Fe + CuSO₄ → FeSO₄ + Cu	Iron displaces copper from its salt solution.
In Biology/Daily Life	Hydrochloric acid + Iron → Iron chloride + Hydrogen gas	Happens during digestion of supplements or iron reactions in the stomach.
-	Chlorine added to water: Cl₂ + H₂O → HOCl + HCl	Chlorine displaces elements and forms compounds that kill germs in drinking water.
Class 10/11 Level	Cu + AgNO₃ → Cu(NO₃)₂ + Ag	Copper displaces silver. It’s used to demonstrate reactivity of metals.
	Cl₂ + 2KBr → 2KCl + Br₂	Chlorine displaces bromine. It’s used to explain displacement among halogens.

 

 

Applications of Displacement Reactions

1. Thermite welding:When Al and combine, the Al being more reactive replaces in . It produces molten iron, used to join railway rails together.
2. Iron extraction: When iron ore is heated with carbon in a giant blast furnace, it extracts the iron from its ore. The iron present in iron ore is displaced by carbon which is an example of a displacement reaction.
3. Acid indigestion: When we drink a sodium hydrogen carbonate solution ( ), our stomach produces more Hydrochloric acid, which can relieve the distress. The hydrogen in hydrochloric acid replaces the sodium from sodium hydrogen carbonate. So we can say the displacement reaction occurs in acid indigestion.
4. PhotosynthesisIn photosynthesis, the carbon dioxide and water with sunlight are converted into food and oxygen. Here, we are discussing this vital process because a displacement reaction occurs in this process. In this process carbon from carbon dioxide replaces the oxygen from water to produce glucose and oxygen. The chemical equation for this process is

Difference Between Single and Double Displacement Reaction

Point	Single Displacement	Double Displacement
What happens?	One element replaces another in a compound.	Two compounds swap their ions.
Formula	A + BC → AC + B	AB + CD → AD + CB
Example	Zn + CuSO₄ → ZnSO₄ + Cu	Na₂SO₄ + BaCl₂ → BaSO₄↓ + 2NaCl
Where seen?	Metal reactions, corrosion	Salt reactions, water treatment
Main change	One element is displaced	Ions are exchanged between compounds

So, this was all about the displacement reactions. We are hopeful that you understood all the concepts related to this topic. For more such Chemistry topics, you can join our platform for free. To do that, you need to download the Testbook App. It will give you access to several study materials like study notes, sample papers, mock tests, etc. So, don’t waste the opportunity and download the app now!

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