Question

The Nernst equation is the one of the most important equations in electrochemistry. At standard temperature, 25 ∘C or 298 K, the equation has the form

E=E∘−(0.0591n)logQ

where E∘ is the standard reduction potential for the reaction in volts and Q is the reaction quotient. The reaction quotient has the usual form

Q=[products]x[reactants]y

A table of standard reduction potentials gives the voltage at standard conditions, 1.00 Mfor all solutions and 1.00 atm for all gases. The Nernst equation allows for the calculation of the cell potential E at other conditions of concentration and pressure.

Using the reaction and the E∘ given below

2Co3+(aq)+2Cl−(aq)→2Co2+(aq)+Cl2(g)      E∘=0.46 V

what is the cell potential at 25 ∘C if the concentrations are [Co3+]= 0.284 M , [Co2+]= 2.00×10⁻²M , and [Cl−]= 0.845 M and the pressure of Cl2 is PCl2= 4.20 atm ?

Express your answer numerically in volts.

E =

Answer 1

Ecell = E⁰cell −(0.0591/n)logQ

E⁰cell is given as 0.46 V

n = 2 in this reaction two electrons transferred

Q = [products]^x[reactants]^y

Q = [Cl2]²[ Co²⁺] / [ Co3+]² [ Cl^-]²

Q = [4.2]²[ 0.02] / [ 0.248]² [ 0.845]²

Q = 8.018

log Q = log (8.018) = 0.9040

plug in all the values in the above equation

Ecell = 0.46 V - 0.059/2 (0.9040)

Ecell = 0.46 V - 0.0266 V

Ecell = 0.433 V