Displacement Reactions

Introduction

Chemical reactions known as displacement reactions occur when a highly reactive element replaces a lesser reactive element from a molecule. Displacement reactions involve both metals & non-metals.

If a chemical participates readily and fast in chemical reactions, it is said to be reactive. Different metals have varying degrees of reactivity. The reactivity of metals can be ordered in a hierarchy. An example of this is a reactivity series. Less reactive metals either take part in chemical reactions very slowly or often not. Metal as well as the complexity of some other metals can both undergo displacement reactions. In a displacement reaction, a more reactive element will take the place of a weaker reactive element in its complex. The reaction has no impact on the weaker reactive metal. It is no longer linked to any additional elements chemically. Now the element is pure.

Displacement Reaction Definition

Displacement reactions are those in which a portion of one reactant is replaced by another reactant. Another name for it is a replacement reaction. as another reactant ion replaces one ion that was previously present.

What is Single Displacement Reaction?

Single displacement reactions are those in which one element displaces another from its salt or complex. Additionally known as single replacement reactions. It is also possible to write general representations -

$$\mathrm{A\:+\:B\:-\:C\:\rightarrow\:A\:-\:C\:+\:B}$$

If A reacts more than B, it will replace B. For instance, potassium substitutes 𝑀𝑔 from magnesium chloride because it is more highly reactive than magnesium.

What is the Reactivity Series?

A reactivity series is a group of metals arranged from highest to lowest reactivity. As a result, the term "metal reactivity series" refers to a group of metals arranged in ascending order of reactivity. It also goes by the name "activity series." Metals' reactivity is caused by either their electronic structure or by the incompleteness of their outer orbitals. As they tend to lose electrons, metals produce positively charged ions. Because their electrons are located distant from the positively charged nucleus, metals with high atomic numbers tend to be highly reactive. Therefore, they are simple to remove.

Types of Chemical Reaction

Synthesis Reactions

When 2 different atoms/ molecules combine to form a new chemical or molecule, this is known as a synthesis reaction.

$$\mathrm{O_{2}\:+\:2H_{2}\:\rightarrow\:H_{2}O}$$

Decomposition Reactions

The 2 main categories of these reactions are as follows

The reaction of Thermal Decomposition

It is a decomposition reaction that is triggered by heat energy

E.g

$$\mathrm{CaCO_{3}\:\rightarrow\:CO_{2}\:+\:CaO}$$

When heated, calcium carbonate breaks down into calcium oxide and carbon dioxide. Quick lime, a crucial component in several industries, is made using this process.

The reaction of Electrolytic Decomposition

Electrical energy is used to give the activation energy for a breakdown in an electrolytic decomposition process. An electrolytic breakdown reaction, such as the water electrolysis, is exemplified by the chemical equation −

E.g

$$\mathrm{H_{2}O\:\rightarrow\:2H_{2}\:+\:O_{2}}$$

Photo Decomposition

In a photodecomposition reaction, the analyte absorbs energy from photons and disintegrates into its constituent elements. The chemical equation following represents a photodecomposition process that breaks down molecular oxygen into an oxygen radical.

E.g.

$$\mathrm{O_{3}\:+\:hv\:\rightarrow\:O_{2}\:+\:O}$$

Replacement Reactions

When an element in a molecule is exchanged for another, the process is referred to as a replacement reaction.

Single-Replacement Reaction

When one element in a molecule is exchanged for another, the process is referred to as a single replacement reaction.

E.g.

$$\mathrm{2K\:+\:2H_{2}O\:\rightarrow\:2KOH\:+\:H}$$

Double-Replacement Reactions

2 novel compounds are created when the components of 2 ionic compounds are exchanged. Double displacement, exchange, or metathesis processes are other names for double replacement reactions.

E.g.

$$\mathrm{Na_{2}SO_{4}\:+\:BaCL_{2}\:\rightarrow\:BaSO_{4}\:+\:2NaCl}$$

Combustion Reactions

A molecule interacts with an oxidant in a combustion reaction, a sort of chemical process that yields heat as well as a fresh product.

E.g.

$$\mathrm{CH_{4}\:+\:O_{2}\:\rightarrow\:CO_{2}\:+\:H_{2}O}$$

Uses of Displacement Reaction

• Aluminium (𝐴𝑙) and ferric oxide are combined to form an alloy for use in welding railway joints $\mathrm{Fe_{2}O_{3}}$.

Reactions −

$$\mathrm{2AL\:+\:Fe_{2}O_{3}\:\rightarrow\:2Fe\:+\:AL_{2}O_{3}}$$

• Fe may be extracted from its ore by a reaction with 𝐶.

$$\mathrm{3C\:+\:Fe_{2}O_{3}\:\rightarrow\:4Fe\:+\:3CO_{2}}$$

• Metals are Extracted

Through a displacement process, it can derive other metals, including 𝐶𝑟.

$$\mathrm{3C\:+\:Cr_{2}O_{3}\:\rightarrow\:4Cr\:+\:3CO_{2}}$$

• Neutralisation of Acids

The formation of 𝐻𝐶𝑙 acid in our stomachs is what causes indigestion. An antacid's base induces the body to respond by displacing itself.

$$\mathrm{Mg(OH)_{2}\:+\:2HCl\:\rightarrow\:MgCl_{2}\:+\:2H_{2}O}$$

Examples of Single Displacement Reaction

• The reaction between $\mathrm{HCl}$ and $\mathrm{Zn}$ −

$$\mathrm{2HCl\:+\:Zn\:\longrightarrow\:ZnCl_{2}\:+\:H_{2}}$$

• The reaction between $\mathrm{Cal_{2}}$ and $\mathrm{Cl}$ −

$$\mathrm{CaCl_{2}\:+\:Cl_{2}\:\longrightarrow\:CaCl_{2}\:+\:l_{2}}$$

Examples of Double Displacement Reaction

• The reaction between $\mathrm{AgNO_{3}}$ & $\mathrm{NaCl}$ −

$$\mathrm{NaCl\:+\:AgNO_{3}\:\rightarrow\:AgCl\:+\:NaNO_{3}}$$

• The reaction between $\mathrm{H_{2}SO_{4}}$ & $\mathrm{LiOH}$ −

$$\mathrm{H_{2}SO_{4}\:+\:2LiOH\:\Longleftrightarrow\:LiO_{2}OH\:+\:2H_{2}O}$$

• The reaction between $\mathrm{[Pb(NO]_{3})_{2}}$ & $\mathrm{NaCl}$ −

$$\mathrm{[Pb(NO]_{3})_{2}\:+\:2NaCl\:\Longleftrightarrow\:2NaNO_{3}\:+\:PbCl}$$

• The reaction between $\mathrm{[Al(SO]_{4})_{3}}$ & $\mathrm{NH_{4}OH}$ −

$$\mathrm{[Al(SO]_{4})_{3}\:+\:6NH_{4}OH\:\rightarrow\:2AL(OH)_{3}\:+\:3[(NH]_{4})_{2}SO_{4}}$$

Applications of Displacement Reactions

Many different disciplines have used displacement reactions. Following are a few of them −

• Thermite welding uses these reactions, where iron is displaced from its oxide by aluminium.

• Steel is made using these reactions, where iron is displaced from its oxide by carbon.

• Most of the time, these reactions are employed in the extraction of metals.

• Acid indigestion is treated by these reactions.

• Photometry of flames by these reactions.

Conclusion

It can be concluded that when one reactant is partially displaced by another, the reaction is referred to as a displacement reaction. Replacement or metathesis reactions are other names for displacement reactions. Double and single displacement reactions are the two different forms of displacement reactions. Cations and anions in the reactants exchange partners to generate products in a process known as double displacement: Single displacement reactions occur when a single reactant partially replaces another.

FAQs

1. What is the displacement reaction's general rule?

One component from a compound replaces another element in a displacement reaction. A much more active element often takes the place of a lower reactive element in its compound. For instance, copper is less reactive than iron. Iron sulphate is created when a piece of iron is introduced to a solution of copper sulphate.

$$\mathrm{Fe\:+\:CuSO_{4}\:\rightarrow\:FeSO_{4}\:+\:Cu}$$

2. Why do metals replace each other?

When the ions of a metal higher up in the electrochemical series are combined with those of metal closer to the bottom, displacement reactions take place.

The ions among the less reactive metal get the electrons that are forced from the atoms of the more reactive metal.

3. What causes an exothermic displacement reaction?

When one element in a molecule is replaced by another, a single-displacement reaction takes place. A chemical reaction either releases or absorbs energy. If energy is released during the process, it is exothermic. Bond formation is an exothermic process.

4. Do all displacement processes include redox?

Yes, all displacement reactions are redox reactions. Consider the interaction between sodium and water. In this reaction, sodium removes hydrogen from the water while simultaneously becoming oxidised by receiving oxygen and reducing the water to hydrogen by removing oxygen.

$$\mathrm{2Na\:+\:2H_{2}O\:\rightarrow\:2NaOH\:+\:H_{2}}$$

5. Can oxidation result in a double displacement reaction?

No. Only a displacement occurs in double displacement reactions. In redox reactions, the number of atoms that are oxidised changes throughout the reaction.