Single Displacement Reaction in Chemistry

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.