[koale]

Can someone give me guides in solving this problem?
Galvanic cell is based on reaction: 2Fe³⁺ (aq) + H₂ (g)  2Fe²⁺ (aq) + 2H⁺ (aq)

Find emf if: [Fe³⁺]=1.75 mol/dm³  ;  P_H2=40.6 kPa  ;  [Fe²⁺]= 1*10^-3 mol/dm³ ; pH=3 in both half-cells.

[Zeeshan Manzoor]

you can find emf of the cell by using Nernst equation which is given as:
                 Ecell=E°-[0.0591]\[n] logK

Here E° is standard emf of cell calculated by eclectrochemical series
        K=[H+]\[Fe+2]
         n is no. of electrons transferred

[koale]

But i dont have [H+]

[Borek]

But i dont have [H+]

Sure you have:

pH=3 in both half-cells.

[koale]

You mean pH=-log[H+]. I get [H+]=10^-3 , same as [Fe²⁺]. And log of 1 is 0. How can I use pressure?

[Zeeshan Manzoor]

so what if you are getting second factor as zero? your answer will be just same as E°
i mean
           Ecell = E°

[koale]

I know that solution is 1.13V. And E^o=0.77V.

[Zeeshan Manzoor]

i solved it in many ways but the answer given by you is not proved therefore i have a serious doubt on conditions given in your question. As hydrogen has greater ability to get oxidized then hydrogen ion concentration should be greater than iron. can you please quote the name of book and chapter where i can find this question

[Borek]

I got 1.03V, but I am too tired to be sure it is a correct solution.

Define the half cells first, then use information given to calculate potential for each separately. You will need to convert pressure to bar to plug it into the Nernst equation.

[koale]

Textbook is not in English. Thank you for help anyway.