A single replacement reaction is a type of chemical reaction where one element replaces another element in a compound. This occurs when a more reactive element displaces a less reactive one. For example, in the reaction between zinc and copper(II) sulfate, zinc replaces copper to form zinc sulfate and copper. These reactions can be represented by the general formula: A + BC → AC + B, where A is the reactive element, and BC is the compound. Single replacement reactions are commonly observed in metals and halogens, and they are important in various applications, including metallurgy and battery technology.