Single Displacement Reaction in Chemistry

Overview of a Single Displacement or Substitution Reaction

In a single displacement or substitution reaction, one element replaces another.
In a single displacement or substitution reaction, one element replaces another. Don Farrall, Getty Images
By
Anne Marie Helmenstine, Ph.D.
Chemistry Expert
  • Ph.D., Biomedical Sciences, University of Tennessee at Knoxville
  • B.A., Physics and Mathematics, Hastings College
Dr. Helmenstine holds a Ph.D. in biomedical sciences and is a science writer, educator, and consultant. She has taught science courses at the high school, college, and graduate levels.
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Anne Marie Helmenstine, Ph.D.
Updated February 08, 2020

A single displacement reaction or substitution reaction is a common and important type of chemical reaction. A substitution or single displacement reaction is characterized by one element being displaced from a compound by another element.
A + BC → AC + B

A single displacement reaction is a specific type of oxidation-reduction reaction. An element or ion is replaced by another in a compound.

Single Displacement Reaction Examples

An example of a substitution reaction occurs when zinc combines with hydrochloric acid. The zinc replaces the hydrogen:
Zn + 2 HCl → ZnCl2 + H2

Here is another example of a single displacement reaction:

3 AgNO3 (aq) + Al (s) → Al(NO3)3 (aq) + 3 Ag (s)

How to Recognize a Substitution Reaction

You can recognize this type of reaction by looking for a trade between one cation or anion in a compound with a pure substance in the reactants side of the equation, forming a new compound in the products side of the reaction.

If, however, two compounds appear to "trade partners", then you're looking at a double displacement reaction rather than a single displacement.

Sources

  • Brown, T.L.; LeMay, H.E.; Burston, B.E. (2017). Chemistry: The Central Science (14th ed.). Pearson. ISBN:9780134414232.