Question

Show that emf of a cell can be used to calculate the equilibrium constant of a cell reaction?

Answer 1

At equilibrium, the reaction quotient Q is the equilibrium constant, K.

This makes the equation:

Ecell = E°cell - (RT/nF) x log10K

From above, we know the following:

Ecell = 0 V

E°cell = +1.13 V

R = 8.3145 J/mol·K

T = 25 &degC = 298.15 K

F = 96484.56 C/mol

n = 6 (six electrons are transferred in the reaction)

Solve for K:

0 = 1.13 V - [(8.3145 J/mol·K x 298.15 K)/(6 x 96484.56 C/mol)]log10K

-1.13 V = - (0.004 V)log10K

log10K = 282.5

K = 10282.5

K = 10282.5 = 100.5 x 10282

K = 3.16 x 10282

Answer:

The equilibrium constant of the cell's redox reaction is 3.16 x 10282