Question

A solution with pH = 6.0 and the total concentration of Cr {(Cr)T = 2.0 x 10-5mol/L} and activity corrections (γs) for an ionic strength of 1.0x 10-3. determine the speciation for Cr among various hydroxy complexes and Cr3+. Stability constants (as base 10 logarithms) are 10.0, 18.3, and 24.0 for Cr(OH)²⁺, Cr(OH)2⁺ and Cr(OH)3⁰ respectively . Assume That the PH does not change with the addition of the metal, no solids form, and the solution behaves ideally. Your answer should include concentrations in moles/L for Cr³⁺, Cr(OH)²⁺, Cr(OH)2⁺, and Cr(OH)3⁰.

Answer 1

Chromium is naturally occurring heavy metal found in the environment commonly in trivalent,Cr(III),and hexavalent Cr(IV)forms.The reduction of Cr(VI) to Cr(III) results in the formation of reactive intermediates that contribute to the cytotoxicity,genotoxicity and carcinogenicity of Cr(VI) containing compounds.The major non occupational source of chromium for humans is food such as vegetables,meat,urban air.Cr3+ is essential to human metabolism at low concentrations.Cr6+ is toxic and carcinogenic.

The effects of water chemical parameters such as pH,presence of halides,alkalinity and iron content were evaluated in environmentally relevant conditions.The existence of these varying parameters was studied at typical drinking water conditions in order to determine any catalyst or inhibitory effects on the oxidation of Cr(III) and subsequent formation of Cr(VI) in the presence of disinfectants