Displacement Reaction

Summary: A reaction where a more reactive element replaces a less reactive element in a compound. Tags: igcse chemistry definition reactions metals Created: 2026-07-14 Last Updated: 2026-07-14

A displacement reaction is a chemical reaction in which a more reactive element replaces a less reactive element from its compound, following the reactivity series. In a typical metal displacement, a more reactive metal such as zinc will displace a less reactive metal ion like copper(II) from its salt solution: Zn(s) + CuSO₄(aq) → ZnSO₄(aq) + Cu(s), with the blue colour of the solution fading as copper metal deposits on the zinc. This principle also applies to the halogens, where a more reactive halogen displaces a less reactive halide ion — for example, chlorine gas displaces bromide ions from potassium bromide solution, turning the solution brown as bromine is formed. Displacement reactions provide a practical method for determining the relative order of reactivity and are the chemical basis for sacrificial protection in corrosion prevention, where a more reactive metal such as zinc is deliberately oxidised in place of iron. IGCSE exam questions frequently ask students to predict whether a reaction will occur by consulting the reactivity series and to write balanced symbol equations with state symbols for the displacement.

Key term — IGCSE Chemistry (0620/0971) glossary.