Question

K = 1.3 * 106 for the disproportionation reaction of Cu+ at 298 K. Calculate the E°cell for this rxn at 298K

The latimer Diagram for Cu+ has:

+0.159 V +0.520 V

Cu2+ ---> Cu+ --> Cu(s)

And then
Cu2+ --> Cu (s) = 0.340 V

So for Ecell would I just do Ecell = (0.520V - (-0.159V))? ... if not how come?

Answer 1

There is another way to solve this problem by using the potential of the half cells.

E_{​​​​​​cell}​​= E_{​​​​​​red}+E_​ox

E_{​​​​​​red} represents reduction half cell(Cu⁺+e^{​​​​​​-} = Cu )and it's value is +0.520 V

E_{​​​​​​ox} represents oxidation half cell (Cu⁺- e^{​​​​​​-} = Cu^{​​​​​2+}) and it's value is -0.159V. Potential for the reduction of Cu^{​​​​​2+} to Cu⁺ is +0.159 V, and for oxidation the half cell reaction is reversed and the potential becomes -(+0.159 V) = -0.159 V and it is represented as E_{​​​​​​ox.}