Science, Tech, Math › Science Heats of Formation Table Enthalpy of Cations and Anions in Aqueous Solution Share Flipboard Email Print PM Images/Getty Images Science Chemistry Periodic Table Basics Chemical Laws Molecules 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 November 04, 2019 The molar heat of formation or standard enthalpy of formation is the change in enthalpy when 1 mole of a substance is formed from its elements under standard state conditions. The standard enthalpy change of formation is the sum of the heats of formation of the products of a reaction minus the sum of the heats of formation of the reactants. Molar Heat of Formation These are molar heats of formation for anions and cations in aqueous solution. In all cases, the heats of formation are given in kJ/mol at 25°C for 1 mole of the ion. Cations ΔHf (kJ/mol) Anions ΔHf (kJ/mol) Ag+ (aq) +105.9 Br- (aq) -120.9 Al3+ (aq) -524.7 Cl- (aq) -167.4 Ba2+ (aq) -538.4 ClO3- (aq) -98.3 Ca2+ (aq) -543.0 ClO4- (aq) -131.4 Cd2+ (aq) -72.4 CO32- (aq) -676.3 Cu2+ (aq) +64.4 CrO42- (aq) -863.2 Fe2+ (aq) -87.9 F- (aq) -329.1 Fe3+ (aq) -47.7 HCO3- (aq) -691.1 H+ (aq) 0.0 H2PO4- (aq) -1302.5 K+ (aq) -251.2 HPO42- (aq) -1298.7 Li+ (aq) -278.5 I- (aq) -55.9 Mg2+ (aq) -462.0 MnO4- (aq) -518.4 Mn2+ (aq) -218.8 NO3- (aq) -206.6 Na+ (aq) -239.7 OH- (aq) -229.9 NH4+ (aq) -132.8 PO43- (aq) -1284.1 Ni2+ (aq) -64.0 S2- (aq) +41.8 Pb2+ (aq) +1.6 SO42- (aq) -907.5 Sn2+ (aq) -10.0 Zn2+ (aq) -152.4 Reference: Masterton, Slowinski, Stanitski, Chemical Principles, CBS College Publishing, 1983. Cite this Article Format mla apa chicago Your Citation Helmenstine, Anne Marie, Ph.D. "Heats of Formation Table." ThoughtCo, Aug. 25, 2020, thoughtco.com/heats-of-formation-table-603969. Helmenstine, Anne Marie, Ph.D. (2020, August 25). Heats of Formation Table. Retrieved from https://www.thoughtco.com/heats-of-formation-table-603969 Helmenstine, Anne Marie, Ph.D. "Heats of Formation Table." ThoughtCo. https://www.thoughtco.com/heats-of-formation-table-603969 (accessed March 7, 2021). copy citation