Single-Displacement Reaction Definition and Examples

The four main types of chemical reactions are synthesis reactions, decomposition reactions, single-displacement reactions, and double-displacement reactions.

Single-Displacement Reaction Definition

A single-displacement reaction is a chemical reaction where one reactant is exchanged for one ion of a second reactant. It is also known as a single-replacement reaction. Single displacement reactions take the form:

A + BC → B + AC

Single-Displacement Reaction Examples

The reaction between zinc metal and hydrochloric acid to produce zinc chloride and hydrogen gas is an example of a single-displacement reaction:

Zn(s) + 2 HCl(aq) → ZnCl₂(aq) + H₂(g)

Another example is the displacement of iron from an iron(II) oxide solution using coke as a carbon source:

2 Fe₂O₃ (s) + 3 C (s) → Fe(s) + CO₂ (g)

Recognizing a Single-Displacement Reaction

When you look at the chemical equation for a reaction, a single-displacement reaction is characterized by one cation or anion trading places with another to form a new product. It's easy to spot when one of the reactants is an element and the other is a compound. Usually, when two compounds react, both cations or both anions will change partners, producing a double-displacement reaction.

You can predict whether a single-displacement reaction will occur by comparing the reactivity of an element using an activity series table. In general, a metal can displace any metal lower in the activity series (cations). The same rule applies to halogens (anions).