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. |
