What formula do I use to calculate E°cell given [Ni2+]= 0.80M and [Co2+]= 0.20M?

Question

Ni2+ +Co -> Ni + Co 2+

Answer 1

You would use the Nernst Equation:

E_cell = Eº_cell - RT/nF ln Q

Q = [Co²⁺]/[Ni²⁺] = 0.20/0.80 = 0.25

n = 2 since 2 electrons are transferred in the redox equation

R = 8.314 J/Kmol

F = Faraday constant = 96,485 C/mol e-

Eº_cell = standard potential = -0.23 V + 0.28 V = 0.05 V

At 25ºC, the Nernst equation can be written as...

E_cell = Eº_cell - (0.0591/n) log Q (combined R, T, and F and converted to natural log)

E_cell = 0.05 - (0.0591/2)(log 0.25) = 0.05 + 0.018

E_cell = 0.068 V