Science, Tech, Math › Science Formation Reaction Definition Share Flipboard Email Print One mole of product is made in a formation reaction. iStock Vectors, 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 July 08, 2019 A formation reaction is a reaction where the one mole of product is formed. Formation Reaction Example Hydrogen and oxygen combine to form water by the formula:2 H2 + O2 → 2 H2OThe formation reaction of this process is:H2 + ½ O2 → H2O Cite this Article Format mla apa chicago Your Citation Helmenstine, Anne Marie, Ph.D. "Formation Reaction Definition." ThoughtCo, Aug. 25, 2020, thoughtco.com/definition-of-formation-reaction-605143. Helmenstine, Anne Marie, Ph.D. (2020, August 25). Formation Reaction Definition. Retrieved from https://www.thoughtco.com/definition-of-formation-reaction-605143 Helmenstine, Anne Marie, Ph.D. "Formation Reaction Definition." ThoughtCo. https://www.thoughtco.com/definition-of-formation-reaction-605143 (accessed January 24, 2021). copy citation