Double Displacement Reactions
Double displacement reactions are those in which two compounds exchange ions to form two new compounds.
These reactions are also called 'partner exchange' reactions. These reactions occur in ionic compounds. For example, in the reaction of copper sulphate and hydrogen sulphide, copper sulphide and sulphuric acid are formed. Thus, the partner of copper is exchanged for the partner of hydrogen in hydrogen sulphide.
CuSO4(aq) + H2S(g) CuS(s) + H2SO4(l)
The reaction of barium chloride and sulphuric acid to form barium sulphate is also a double decomposition reaction.
BaCl2(aq) + H2SO4(l) BaSO4(s) + 2HCl(aq)
The neutralisation reactions are also double decomposition reactions.
NaOH(aq) + HCl(aq) NaCl(aq) + H2O(l)