Heats of Formation Table for Cations and Anions

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 25Â °C for 1 mole of the ion. Cations Hf (kJ/mol) Anions Hf (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.