The examination of the activity coefficients of Cu(II) complexes with OH- and Cl- in NaClO4 using pitzer equations: Application to other divalent cations

J. M. Santana-Casiano, M. González-Dávila, F. J. Millero

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9 Scopus citations


The stability constants for the hydrolysis of Cu(II) and formation of chloride complexes in NaClO4 solution, at 25∈°C, have been examined using the Pitzer equations. The calculated activity coefficients of CuOH+, Cu(OH)2, Cu2(OH)3+, Cu 2(OH) 2 2+ , CuCl+ and CuCl 2 have been used to determine the Pitzer parameter (β i (0) , β i (1) , and C i ) for these complexes. These parameters yield values for the hydrolysis constants (log∈10 β 1 * , log∈10 β 2 * , log∈10 β 2,1 * and log∈10 β 2,2 * ) and the formation of the chloride complexes (log∈10 β CuCl * and log10βCuCl2 that agree with the experimental measurements, respectively to ±0.01, ±0.02,±0.03,±0.06,±0.03 and ±0.07. The stability constants for the hydrolysis and chloride complexes of Cu(II) were found to be related to those of other divalent metals over a wide range of ionic strength. This has allowed us to use the calculated Pitzer parameters for copper complexes to model the stability constants and activity coefficients of hydroxide and chloride complexes of other divalent metals. The applicability of the Pitzer Cu(II) model to the ionic strength dependence of hydrolysis of zinc and cadmium is presented. The resulting thermodynamic hydroxide and chloride constants for zinc are log10βZnOH+=-9.04±0.04 and log10βZn(OH)2=-16.90±0.02. For cadmium the thermodynamic hydrolysis constants are log10βCdOH+=- 10.24±0.05 and log10βCd(OH)2=-20.42±0. 07. The Cu(II) model allows one to determine the stability of other divalent metal complexes over a wide range of concentration when little experimental data are available. More reliable stepwise stability constants for divalent metals are needed to test the linearity found for the chloro complexes.

Original languageEnglish (US)
Pages (from-to)749-762
Number of pages14
JournalJournal of Solution Chemistry
Issue number6
StatePublished - Jun 2008


  • Chloride complexes
  • Copper complexes
  • Cu(II) hydrolysis
  • Stability complexes

ASJC Scopus subject areas

  • Biophysics
  • Biochemistry
  • Molecular Biology
  • Physical and Theoretical Chemistry


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