Which is not a sign that a double displacement reaction has occurred?
question 15 options:

gas may be formed

water may be produced

a precipitate is formed

the coefficients are equal

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.