Displacement Reaction

Displacement Reaction, also known as single replacement reaction, is a chemical reaction in which one element displaces another element in a compound. In this reaction, the less reactive element is replaced by a more reactive element or metal which results in the formation of a new substance.

In this article, we will discuss displacement reactions, single displacement reactions, and double displacement reactions along with their examples.

What is a Displacement Reaction?

When a more reactive atom replaces or displaces a less reactive atom in the course of a reaction and forms a new substance, then such a reaction is called Displacement Reaction. Both metals and non-metals can participate in a displacement reaction but a metal can only replace other metals and a nonmetal will only replace a nonmetal.

In a displacement reaction, only one atom is displaced, hence displacement reaction is also called a Single Replacement Reaction.

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• Chemical Reactions
• Types of Chemical Reactions

Displacement Reaction Definition

Displacement Reaction is a chemical reaction in which a more reactive element takes the place of a less reactive element. Both metals and nonmetals are involved in this type of reaction. This is also known as a single replacement or exchange reaction.

Displacement Reaction Equation

The general form of displacement reaction can be written simply as follows:

A + CD → AD + C

In the above reaction, A is more reactive than C and so a displacement reaction occurred here.

Examples of Displacement Reaction

Here are a few examples related to the different types of Displacement Reaction:

• Mg + 2HCl → MgCl₂ + H₂
• Zn + CuSO₄ → ZnSO₄ + Cu
• Cl₂ + 2NaBr→ 2NaCl + Br₂
• CH₄ + Cl₂ → CH₃Cl + HCl

These Reactions are further classified based on the kind of element participating in the chemical reaction. They are explained below:

Metal Displacement Reaction

Some metals are more reactive than others and so a metal displacement reaction takes place. In a metal displacement reaction, a highly reactive metal replaces a less reactive metal and forms a new salt.

The reactivity of a metal can be described according to their position in the reactivity series. The metals placed above are more reactive than all other metals that are below them. An example of a metal displacement reaction is given below:

Zn + CuSO₄ → ZnSO₄ + Cu

In the above reaction, Zinc is a more reactive metal than copper and hence replaces copper in copper sulphate solution.

Here are a few more examples of metal displacement reactions:

• Mg(s) + 2HCl(aq) → MgCl₂(aq) + H₂(g)
• 2Al(s) + Fe₂O₃(s) → Al₂O₃(s) + 2Fe(s)

Halogen Displacement Reaction

The Halogen Displacement Reaction occurs when a less reactive halide is replaced by a more reactive halogen in a compound. In the displacement reaction, the more reactive halogen atoms oxidize the less reactive halide ions, causing the halide ions to lose electrons and form halogen atoms. The halogen atoms then gain electrons to form halide ions, that are reduced.

An example for the Halogen Displacement Reaction is illustrated below:

Cl₂ + 2Kl → 2KCl + l₂

Here are a few more examples of halogen displacement reactions:

• F₂(g) + 2 NaI (aq) → 2 NaF (aq) + I₂ (s)
• Br₂ (aq) + CaCl₂ (aq) → CaBr₂ (aq) + Cl₂ (g)

Hydrogen Displacement Reactions

In the hydrogen displacement reaction, the hydrogen in the acid is replaced by an active metal. Many metals react rapidly with acids and are so reactive that they can replace hydrogen in water. The products of this reaction are metal hydroxide and hydrogen gas.

An example of a Hydrogen displacement reaction is given below:

2K + 2H₂O → 2KOH + H₂

A few more example of hydrogen displacement reactions include:

• Mg(s) + 2HCl(aq) → MgCl₂(aq) + H₂(g)
• CaH₂(s) + 2H₂O(l) → Ca(OH)₂(aq) + 2H₂(g)

Reactivity Series

Reactivity series is a series of metals in order of their reactivity from highest to lowest. It is used to determine the products of single displacement reactions, where metal A will replace another metal B in solution if A is higher in the series.

A metal can displace the metal listed below it in the reactivity series, but not above it. For example, zinc is more active than copper and is able to displace copper ions from the solution. The following reaction will take place:

Zn(s) + Cu²⁺ → Zn²⁺ (aq) + Cu(s)

However, silver cannot displace the copper ions from the solution as it is less reactive than the copper.

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Displacement Reaction Diagram

The diagram of the displacement reaction is given below:

Let us consider a simple experiment to understand the above reaction in a more efficient way:

Materials Required

Following are the materials required for the experiment:

• test tube
• iron nail
• copper sulphate solution

Theory

According to the reactivity series, more reactive metals displace less reactive metals. When iron is compared with copper, it is placed above copper in the reactivity series. Therefore, iron being more reactive tends to replace the less reactive metal(copper).

Procedure

Follow the given steps to conduct the experiment:

• Wash and dry the test tube.
• Add 30 mL of blue copper sulphate solution inside the test tube
• Take an iron nail and dip it in CuSO₄ in the test tube for about 15 minutes.
• Observe the intensity of the blue color of CuSO₄ before and after the experiment conducted in a test tube. The following reaction will take place:

Fe(s) + CuSO₄(aq) → FeSO₄(aq) + Cu(s)

Observation

When an iron nail is placed in CuSO₄ solution, iron displaces copper from the copper sulphate solution to form a ferrous sulphate solution. A brownish-red layer of copper metal gets deposited on iron nails.

Experiment	Before	After
Colour of CuSO4	Blue	Green
Colour of iron nail	Silvery grey	Brownish red coating

Types of Displacement Reaction

The displacement reaction is broadly classified into two types namely:

• Single Displacement Reaction
• Double Displacement Reaction

Single Displacement Reaction

Single Displacement Reaction is a reaction in which one element is displaced by another element of a compound. This reaction is a specific type of oxidation-reduction chemical reaction. In this reaction, a change of colour is observed, however, no precipitate is formed in this reaction. Since this reaction involves the displacement of one element only therefore it is also known as a Single Replacement Reaction.

The general form of a single-displacement reaction is illustrated as:

A + BC → B + AC

Single Displacement Reaction Definition

Single displacement reaction is a type of oxidation-reduction chemical reaction in which an ion or element moves out of a compound, i.e., one element in a compound is replaced by another element.

Single Displacement Reaction Examples

When chlorine is reacted with sodium bromide, sodium chloride and bromine is formed. This reaction is as follows:

Cl₂(aq) + 2NaBr(aq) → NaCl + Br₂(aq)

In this reaction, Bromine is replaced by chlorine which results in the formation of sodium chloride.

Two more examples of Single Displacement Reaction are:

• Mg (s) + 2HCl (aq) → MgCl₂ (aq) + H₂ (g)
• 2K (s) + 2H₂O (l) → 2KOH (aq) + H₂ (g)

Double Displacement Reaction

Double Displacement Reaction is a reaction in which two compounds exchange their elements which results in the formation of two new compounds. In this reaction, a precipitate is formed when the cations from one of the reactants react with the anion of the other reactant.

The general form of a double-displacement reaction is illustrated as:

AB + CD → AD + CB

Double Displacement Reaction Definition

The chemical reaction in which ions are exchanged between two compounds and two new compounds are formed is called Double Displacement Reaction.

Since two displacements take place in this reaction, hence it is called double displacement reaction. It is also known as Double Replacement Reaction or Salt Metathesis Reaction.

A double displacement reaction can be represented as follows:

Double Displacement Reactions Example

When barium chloride solution is mixed with sodium sulphate solution, barium sulphate and sodium chloride are formed. This reaction is as follow:

Na₂SO₄ + BaCl₂ → BaSO₄ + 2NaCl

In this reaction, sulphate and chloride ions are exchanged between sodium sulphate and barium chloride, due to which barium sulphate and sodium chloride are formed. This reaction results in the formation of a white precipitate of barium sulphate.

Below are the few more examples of double displacement reaction:

• AgNO₃ (aq) + NaCl (aq) → AgCl (s) + NaNO₃ (aq)
• HCl (aq) + KOH (aq) → KCl (aq) + H₂O (l)

Difference Between Single Displacement and Double Displacement Reaction

The difference between Single displacement and double displacement reaction is given below:

Aspect	Single Displacement Reaction	Double Displacement Reaction
Definition	In Single Displacement Reaction, a single element replaces a less reactive element in a compound.	In Double Displacement Reaction, two compounds swaps their elements to form two new compounds.
General Formula	AB + C → A + BC	AB + CD → AC + BD
Formation of Percipitate	In this reaction, a change in colour takes place but no precipitate is formed.	In this reaction, a formation of percipitate takes place.
Application	Electrolytic Refining, Metal Extraction	Acid-base neutralization, Water Softening
Example	Zn + CuSO4 → ZnSO4 + Cu	AgNO3 + NaCl → AgCl + NaNO3

Applications of Displacement Reactions

Displacement reaction has a wide range of applications in Chemistry, few of them are:

• Displacement Reaction are used in extraction of the metals from its ore.

• It is used in thermite welding in which aluminum displaces iron from its oxide.

• Acid-base neutralization is also an important application of this reaction.

• Displacement reaction is also used in the formation of steel where carbon displaces iron from its oxide.

• It is also used in the production of hydrogen gas.

• This reaction also helps in prevention of metals from corrosion.

• Displacement Reaction can also be used in the flame photometry.

Displacement Reaction: FAQs

What is Displacement Reaction? Give Two Examples.

A reaction in which a less reactive element is replaced by a more reactive element is known as a displacement reaction. Two examples of displacement reactions are:

• Fe + CuSO₄ → FeSO₄ + Cu
• Zn + FeSO₄ → ZnSO4 + Fe

What is the Rule of Displacement Reaction?

The rule of displacement reaction is that a more reactive element replaces a less reactive element in a compound.

What are 5 examples of Double Displacement Reaction?

The examples of double displacement reaction are as follows:

• Mg + Cu(NO₃)₂ → Mg(NO₃)₂ + Cu
• AgNO₃ + NaCl → AgCl + NaNO₃
• HCl + KOH → KCl + H₂O
• Na₂SO₄ + BaCl₂ → BaSO₄ + 2NaCl
• Zn + 2 HCl → ZnCl₂ + H₂

What is Single Displacement Reaction?

A single displacement reaction is reaction in which one element replaces a similar but less reactive element in a compound.

What is the General Form of Displacement Reaction?

The general form of displacement reaction is as follows:

A + CD → AD + C