Single Displacement Reaction Definition and Examples

What You Need to Know About Single Displacement Reactions

One reactant exchanges for one ion in a single displacement reaction.
One reactant exchanges for one ion in a single displacement reaction. Westend61 / Getty Images

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

Basically, when you look at the chemical equation for a reaction, a single displacement reaction is characterized by one cation or anion trading place 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 or not a single displacement reaction will occur by comparing the reactivity of element using an activity series table. In general, a metal can displace any metal lower in the activity series (cations). The same rule applies for halogens (anions).