ELECTRODE POTENTIALS AND THERMODYNAMIC DATA FOR AQUEOUS IONS . COPPER ZINC CADMIUM IRON COBALT AND NICKEL

Heats of solution of CuSO4(c), ZnSO4(c), CdSO4(c), hydrates of these compounds, and hydrates of FeSO4(c) have been measured. These data lead to ΔHf°, S̄2°, and ΔGf° values for the M2+(aq) ions. Standard potentials are calculated from the ΔGf° values and are compared with standard potentials previously derived from electrochemical measurements. Of particular interest is our E° = 0.473 V for Fe-Fe2+(aq) compared with E° = 0.409, 0.440, and 0.467 V from earlier electrochemical measurements. We also obtain ΔGf°, ΔHf°, and S̄2° values for Fe3+(aq).