Determination of the Hydrolysis Constants and Solubility Product of Chromium(III) from Reduction of Dichromate Solutions by ICP-OES and UV-Visible Spectroscopy

作者：Lopez Gonzalez H; Peralta Videa J R; Romero Guzman E T; Rojas Hernandez A; Gardea Torresdey J L^*

来源：Journal of Solution Chemistry, 2010, 39(4): 522-532.

DOI：10.1007/s10953-010-9522-0

• Chromium
• Hydrolysis
• Stability constant
• pCr-pC(H) diagram
• UV-Vis spectroscopy

The determination of equilibrium constants is difficult when several chemical species are simultaneously present in solution. In this investigation, optical emission spectroscopic determinations of chromium(III) concentration in a 10(-4) mol.dm(-3) solution, prepared from K(2)Cr(2)O(7) reduced in HNO(3) or HCl media, were used to construct the pCr((aq))-pC(H) diagram. This diagram was used to calculate the pC(H) borderline of precipitation, to estimate the solubility product (log(10) K(sp, Cr(OH)3)*), and the hydrolysis constants (log(10)beta(Cr,) (H)*, log(10)beta(Cr, 2H)*, and log(10)beta(Cr, 3H)*) of Cr(III). The hydrolysis constants were also calculated using the SQUAD and SUPERQUAD software, along with the average ligand number method. UV-Vis absorption data and associated variables were used in SQUAD, SUPERQUAD, and the average ligand calculations. Results are: 9.00 +/- 0.04 for the pC(H) at the onset of precipitation, 12.40 for log(10)K(sp, Cr(OH)3)*, -3.52 +/- 0.02 for log10 beta(Cr, H)*, -9.30 +/- 0.87 for log10 beta(Cr, 2H)* and -17.18 +/- 0.16 for log(10) beta(Cr, 3H)*, respectively. All methods produced essentially the same values for the hydrolysis constants of Cr(III).

• 出版日期2010-4