Science, Tech, Math › Science Double Replacement Reaction Definition Double Displacement or Metathesis Reaction Share Flipboard Email Print Ions are exchanged in a double displacement reaction. Comstock, Getty Images Science Chemistry Chemical Laws Basics Molecules Periodic Table Projects & Experiments Scientific Method Biochemistry Physical Chemistry Medical Chemistry Chemistry In Everyday Life Famous Chemists Activities for Kids Abbreviations & Acronyms Biology Physics Geology Astronomy Weather & Climate By Anne Marie Helmenstine, Ph.D. Chemistry Expert Ph.D., Biomedical Sciences, University of Tennessee at Knoxville B.A., Physics and Mathematics, Hastings College Dr. Helmenstine holds a Ph.D. in biomedical sciences and is a science writer, educator, and consultant. She has taught science courses at the high school, college, and graduate levels. our editorial process Facebook Facebook Twitter Twitter Anne Marie Helmenstine, Ph.D. Updated June 03, 2019 A double replacement reaction is a chemical reaction where two reactant ionic compounds exchange ions to form two new product compounds with the same ions. Key Takeaways: Double Replacement Reaction A double replacement reaction is a type of chemical reaction that occurs when two reactants exchange cations or anions to yield two new products.Double replacement reactions are also called double replacement reactions, double displacement reactions, or metathesis reactions.Neutralization, precipitation, and gas formation are types of double replacement reactions. Double replacement reactions take the form: A+B- + C+D- → A+D- + C+B- In this type of reaction, the positive-charged cations and the negative-charged anions of the reactants both trade places (double displacement), to form two new products. Also Known As: Other names for a double displacement reaction are a metathesis reaction or a double replacement reaction. Examples of Double Replacement Reactions The reaction: AgNO3 + NaCl → AgCl + NaNO3 is a double replacement reaction. The silver traded its nitrite ion for the sodium's chloride ion. Another example is the reaction between sodium sulfide and hydrochloric acid to form sodium chloride and hydrogen sulfide: Na2S + HCl → NaCl + H2S Types of Double Displacement Reactions There are three classes of metathesis reactions: neutralization, precipitation, and gas formation reactions. Neutralization Reaction - A neutralization reaction is an acid-base reaction which yields a solution with a neutral pH. Precipitation Reaction - Two compounds react to for a solid product called a precipitate. The precipitate is either slightly soluble or else insoluble in water. Gas Formation - A gas formation reaction is one which yields a gas as a product. The example given earlier, in which hydrogen sulfide was produced, was a gas formation reaction.