Single Displacement Reaction

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.
Updated March 06, 2017

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.