What characterizes a double replacement reaction?

A double replacement reaction is specifically characterized by the exchange of ions between two compounds, typically ionic compounds. In this type of reaction, the cations and anions of the reactants swap partners to form two new compounds. This process can be visualized in a generalized equation format, where AB and CD (representing two ionic compounds) react to produce AD and CB.

This definition holds true as double replacement reactions often occur in aqueous solutions where the compounds dissociate into their respective ions. These reactions usually result in the formation of a precipitate, a gas, or a weak electrolyte (like water), highlighting the reorganization of ions.

The other options describe different types of reactions. For instance, a single replacement reaction involves one element taking the place of another element in a compound, while synthesis (or combination) reactions refer to the formation of a compound from simpler substances. Decomposition reactions break down a compound into its constituent elements or simpler compounds. Understanding these different reaction types is essential for grasping the broader concepts of chemical reactions.