We´ll
start with ion’exchange reactions.
In
these reactions solutions of two compounds exchange ions.
For example, if the following reaction did occur as written, then the
reaction would be classified as ion-exchange reaction
2 NaCl (aq) + Pb(NO3)2 (aq) ® PbCl2 + 2 NaNO3
Since both the reactants are in
solution, they contain free aqueous ions, namely Na+ (aq), Cl- (aq), Pb2+ (aq) and NO3- (aq).
What
has basically appeared to have taken place is the exchange of the ions; sodium and lead have swapped their anions, hence the name ion-exchange reaction.
Such
reactions may also be referred to as double-displacement reaction
or metathesis
reaction or precipitation reaction.