Those reactions in which two compounds react by an exchange of ions to form two new compounds are called double displacement reactions. In double replacement reactions, the positive ions exchange negative ion partners. A double replacement reaction is represented by the general equation.
AB + CD → AD + CB
In a double displacement reaction, atoms from two different compounds switch places. The reactants are two compounds and the products are two different compounds. Double displacement reactions can also be called double replacement reactions.
Fe2O3 + 6HCl → 2FeCl3 + 3H2O
Many double displacement reactions occur between ionic compounds that are dissolved in water.