Displacement reaction is a chemical reaction in which a more reactive element displaces a less reactive element from its compound. Both metals and non-metals take part in displacement reaction. An example of a single replacement reaction is the reaction of iron nails with copper sulphate solution. An important thing to remember with single displacement reaction is that elements that form cations can only displace cations and elements that form anions can only displace anions. There are two types of single displacement reactions : (a) Cation Replacement Reaction and (b) Anion Replacement Reaction. In cation replacement reaction, one cation replaces another one from its solution. All metal displacement reactions are cation replacement reactions. In anion replacement reaction, one anion replaces another one from its solution. For example, more reactive halogen replaces less reactive halogen from its solution.
This video explains how to study a single displacement reaction with the help of iron nails and copper sulphate solution.