| Popis: |
Solubility constants, *Kpso = [Fe2+]P [H+]−2, of iron(II) sulphide phases such as troilite, FeS, hexagonal pyrrhotite, FeS1,11, and natural monoclinic pyrrhotite, FeS1,14, have been determined at 323.15 K and total anionic molality, I = 1.0 mol kg−1 (Na)ClO4. At the same conditions the equilibrium constant for the reaction Fe2+ + 2Tl(s) ≈ Fe(s) + 2Tl+ was measured and used for the evaluation of the standard electrode potential of Fe2+/Fe. The respective solubility constants combined with the standard electrode potential of Fe2+/Fe and the well known thermodynamic data of hydrogen sulphide led to the free enthalpies of formation, ΔfG⊖ of the above mentioned iron(II) sulphide phases. Nickel(II) carbonate, NiCO3, was synthesized and its solubility constant determined at 348.15, 358.15 and 363.15 K and at I = 1.00 and 0.20 mol kg−1 (Na)ClO4. From the results obtained the ΔfG⊖ of NiCO3 was calculated and turned out to be considerably more negative (> 30 kJ mol−1) than the value previously accepted. |
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