Question

For the reaction 2Co3+(aq)+2Cl−(aq)→2Co2+(aq)+Cl2(g). E∘=0.483 V what is the cell potential at 25 ∘C if the concentrations are [Co3+]= 0.222 M , [Co2+]= 0.275 M , and [Cl−]= 0.309 M and the pressure of Cl2 is PCl2= 3.80 atm ?

Answer 1

Calculate the value for the reaction quotient, Q. (Note: We calculate Q using molar concentrations for solutions and pressures for gases.)

Q = [CO₂]².pCl₂/[CO₃]²[Cl^-]²

Q = 61.0697

Now, number of moles of electrons transferred in the balanced equation, n=2

E_cell, the cell potential at the non-standard state conditions using the Nernst equation.

E_cell = E^o_cell - (RT/nF) ln Q

            E_cell = cell potential at non-standard state conditions
            E^o_cell = standard state cell potential
            R = constant (8.31 J/mole K)
            T = absolute temperature (Kelvin scale)
            F = Faraday's constant (96,485 C/mole e^-)
            n = number of moles of electrons transferred in the balanced equation for the reaction occurring
                  in the cell
            Q = reaction quotient for the reaction.

Putting the standard values,

E_cell = E^o_cell - (0.0257/n) ln Q

= 0.483 - 0.0528 = 0.4302 Volts