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Chemistry Forums for Students => Undergraduate General Chemistry Forum => Topic started by: Ciubba on April 20, 2015, 08:03:27 PM

Title: Solubility Question
Post by: Ciubba on April 20, 2015, 08:03:27 PM
Calculate the solubilities of Cd(OH)2(s) and Fe(OH)3(s) as a function of pH, then determine at what pH range the two hydroxides can be separated.

I can get that the solubility of Cd(OH)2 is (7.2*1013)*[H3O+]2 and that the solubility of Fe(OH)3 is (2.8*103)*[H3O+]3, which agrees with the book's answer. However, I cannot figure out how the book determined that the pH range of separability is from 2 to 8-- could someone point me in the right direction?
Title: Re: Solubility Question
Post by: Borek on April 21, 2015, 02:47:02 AM
It means one precipitates, the other doesn't. Actually exact values are a function of concentrations of both cations, so the question - as stated - is not possible to answer precisely, unless your book defined what it means by separation.