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Chemistry Forums for Students => Undergraduate General Chemistry Forum => Topic started by: mburn on October 24, 2019, 08:31:02 PM

Title: Nernst equation and Fe3+/Fe2+ ratio help
Post by: mburn on October 24, 2019, 08:31:02 PM

Hello! We've been given this problem

Show that when pH = 5.5  [Fe3+]/[Fe2+] = 200
Given E°(O2/H2O) = 1.23 V
Eº (Fe3+/Fe2+) = 0.77 V
And Ecell=0.46V

I think I know roughly what to do but am a bit confused, because doesn't the E° of this equation also equal 0.46V so any reaction quotient will come out as equal to zero? Or am I misunderstanding something?

Thank you very much

Title: Re: Nernst equation and Fe3+/Fe2+ ratio help
Post by: Borek on October 25, 2019, 02:44:51 AM

Quote from: mburn on October 24, 2019, 08:31:02 PM

doesn't the E° of this equation also equal 0.46V

Of which equation?

Quote

any reaction quotient will come out as equal to zero

Reaction quotient calculated from the Nernst equation can never be zero.