Single displacement is a type of chemical reaction where one element replaces another element in a compound. This reaction typically occurs between a more reactive element and a less reactive one. For example, when zinc reacts with hydrochloric acid, the zinc displaces hydrogen from the acid, forming zinc chloride and releasing hydrogen gas. In a single displacement reaction, the general formula can be represented as A + BC → AC + B. Here, A is a free element, and BC is a compound. This reaction is common in various applications, including metal extraction and the production of gases.