October 10, 2015

Homework Help: Re: chemistry

Posted by Brunette on Saturday, December 8, 2012 at 8:10pm.

The average pH of open ocean water is 8.1. What is the maximum value of [Fe3+] in pH 8.1 seawater if the Ksp of Fe(OH)3 is 1.1*10^-36?
chemistry - DrBob222, Friday, December 7, 2012 at 10:14pm
Fe(OH)3 ==> Fe^3+ + 3OH^-
pH = 8.1
pH + pOH = pKw = 14
Therefore, pOH = 14-8.1 = ?
pOH = -log(OH^-) and
(OH^-) = ?
Ksp = (Fe^3+)(OH^-)^3
Substitute Ksp and OH^- from above into Ksp expression and solve for Fe^3+.

I cant seem to get the right answer. I have no idea if I'm doing it right. So when you subtract 8.1 from 14, you get 5.9. Is that the value for OH that you plug into the pOH equation?

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