the coefficients are equal is NOT a sign that a double displacement reaction has occurred
Explanation:
Usually during solutions of two ionic compounds are combined a precipitate (solid) is created. The mix may become cloudy, or may also separate, with the solids falling at the seat of the receptacle. Infrequently, the mix may bubble as a gas or water is produced.
A precipitation reaction is at two aqueous ionic compounds that make a unique ionic compound that is not soluble in water. The insoluble product compound is called the precipitate. The reaction, in this case, is not balanced, which are evaluated by summing coefficients.