A double displacement reaction is a type of chemical reaction where two compounds exchange ions or elements to form two new compounds. This often occurs in aqueous solutions, where the reactants are typically ionic compounds. The general formula can be represented as AB + CD → AD + CB, where A and C are cations, and B and D are anions. These reactions are commonly seen in processes like precipitation and neutralization. For example, when silver nitrate reacts with sodium chloride, they exchange ions to form silver chloride, a precipitate, and sodium nitrate, which remains dissolved in the solution.