Question

Calculate the Ecell and ΔG of redox reactions at 25 degrees Celsius with the following conditions:

a) n = 1 and K = 5.0 x 10^-6

b) n = 2 and K = 0.065

Answer 1

using equation, G=Go+RT ln Q   [Q=reaction quotient,at equilibrium G=0 and Q=K]

Go=-RT ln K

   R=8.314 J/K.mol (universal gas constant)

T=25+273=298K

Go=-(8.314 J/K.mol)*298K ln (5.0*10^-6)=-(8.314 J/K.mol)*298K *2.030 log (5.0*10^-6)=30246.87 J/mol=30.246 KJ/mol

Also Go=-nFEocell

30246.87 J/mol=-(1mol electron)*(96485 C/mol)*Eocell                    [F=faraday's constant, C=J/V]

Eocell=-30246.87J/96485 J/V=-0.31V

b)

Go=-(8.314 J/K.mol)*298K ln (0.065)=-(8.314 J/K.mol)*298K *2.030 log (0.065)=6773.336 J/mol=Go

for n=2 mol

Go=6773.336 J/mol* 2 mol =13546.672 J/mol=13.546 KJ/mol

Also Go=-nFEocell

6773.336 J/mol=-(2mol electron)*(96485 C/mol)*Eocell                    [F=faraday's constant, C=J/V]

Eocell=-6773.336J/96485 J/V=-0.070 V