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Topic: Calculate concentration ratio  (Read 2302 times)

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Offline kdbmvp

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Calculate concentration ratio
« on: April 12, 2019, 07:57:23 AM »
Hello,

If we have the half-reactions:

Fe3++e- -> Fe2+
and
2H+ + 2e- -> H2

Calculate the ratio [Fe3+] / [Fe2+] at pH 2. Any hint? I was immediately thinking standard electrode potentials as we have two half reactions, but not sure exactly how to go on..

Offline kdbmvp

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Re: Calculate concentration ratio
« Reply #1 on: April 13, 2019, 03:20:52 AM »
Anyone?

Offline isears

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Re: Calculate concentration ratio
« Reply #2 on: April 14, 2019, 11:09:48 AM »
I think you're going to need the Nernst equation for this. The Nernst equation relates standard electrode potentials and Q, which is a function of the concentrations, to include the concentration of H+, which will eventually finally yield pH if you take -log.

Check out this khan academy vid!

https://www.khanacademy.org/test-prep/mcat/physical-processes/intro-electrochemistry-mcat/v/nerst-equation-edited

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