Difference Between Single Displacement and Double Displacement Reaction

The key difference between single displacement and double displacement reaction is that, in single displacement reactions, one chemical species replaces a part of another chemical species whereas, in double displacement reactions, exchange of two ionic species between two molecules occur.

Single displacement and double displacement reactions are important chemical reactions that involve both bond formation and bond breaking. Thus, it is important to know the exact difference between single displacement and double displacement reaction.

1. Overview and Key Difference
2. What is Single Displacement Reaction
3. What is Double Displacement Reaction
4. Side by Side Comparison – Single Displacement vs Double Displacement Reaction in Tabular Form
5. Summary

What is Single Displacement Reaction?

A single displacement reaction is a type of chemical reaction in which one chemical species replaces a part of another chemical species. For this type of reaction to occur, there should be a reactive species which can displace a part of a molecule (such as a functional group). Mostly, the reactive species is a cation, anion or a metal. The general formula for this type of reactions is as follows:

A-B + C ⟶ A + B-C

Here, B is a part of the AB molecule, and it is replaced by a reactive species C. Thereafter, the BC molecule is formed. We can predict the result of a displacement reaction by looking at the reactivity series. Here, the chemical elements at the top of the series can replace the chemical elements in the bottom of the series. Let us consider an example;

Zn + 2HCl ⟶ ZnCl₂ + H₂

In the above example, Zn is at the upper region of the reactivity series while H is in the lower region; therefore, Zn can replace H in HCl and forms ZnCl₂.

What is Double Displacement Reaction?

Double displacement reactions are a type of chemical reactions in which an exchange of two ionic species between two molecules occurs. The general formula is as follows:

A-B + C-D ⟶ A-C + B-D

Difference Between Single Displacement and Double Displacement Reaction

Figure 01: Precipitation of Silver on Copper

The bond that breaks and forms during this reaction can be either ionic or covalent bonds. Some examples of this type of reactions include precipitation reactions, acid-base reactions, alkylation, etc.

What is the Difference Between Single Displacement and Double Displacement Reaction?

Single and double displacement reactions are two types of chemical reactions that are important in isolating the desired component from a solution. The key difference between single displacement and double displacement reaction is that in single displacement reactions, one chemical species replaces a part of another chemical species whereas, in double displacement reactions, exchange of two ionic species between two molecules occurs. Single displacement reactions need to have a reactive species that can replace a functional group while double displacement reactions need to have exchangeable ions. So, this is another difference between single displacement and double displacement reaction.

Moreover, Zn replacing H in HCl and forming ZnCl₂is an example of a single displacement reaction, whereas precipitation reactions, acid-base reactions, alkylation, etc. are examples of double displacement reactions.