Zur Thermodynamik der Metallcarbonate 3. Mitteilung [1]. Löslichkeitskonstanten und Freie Bildungsenthalpien von ZnCO 3 und Zn 5 (OH) 6 (CO 3 ) 2 bei 25°

The solubilities of ZnCO 3 and Zn 5 (OH) 6 (CO 3 ) 2 have been investigated at 25°C in solutions of the constant ionic strength 0,2 M consisting primarily of sodium perchlorate. From experimental data the following values for equilibrium constants and G IBBS free energies of formation are deduced:\documentclass{article}\pagestyle{empty}\begin{document}$$ {\rm ZnC}O_3 :\log [{\rm ZN}^{2 +}]P{\rm co}_2 [{\rm H}^ +]^{- 2} = 7.57_4 \pm 0,02_3 (I = 0.2M),7.35_3 \pm 0.03_7 (I = 0); $$\end{document}\documentclass{article}\pagestyle{empty}\begin{document}$$ \Delta G_{f\, 298.2}^0 = - 176.10 \pm 0.04\,{\rm kcal}/{\rm mole}, $$\end{document}\documentclass{article}\pagestyle{empty}\begin{document}$$ {\rm Zn}_5 ({\rm OH})_6 ({\rm CO}_3)_2 :\log [{\rm Zn}^{2 +}]P_{{\rm CO}_{\rm 2}}^{{\rm 0}{\rm .4}} [{\rm H}^ +]^{- 2} = 9.41_7 \pm 0.04_0 (I = 0.2{\rm M}),9.19_9 \pm 0.05_0 (I = 0); $$\end{document}\documentclass{article}\pagestyle{empty}\begin{document}$$ \Delta G_{f\,298.2}^0 = - 755.20 \pm 0.13\,{\rm kcal}/{\rm mole}. $$\end{document}A predominance area diagram for the ternary system Zn 2+ –H 2 O–CO 2( g ) including ZnO, ZnCO 3 , Zn 5 (OH) 6 (CO 3)2 , and Zn 2+ is given.