Calculate E(initial), delta G(initial), and K for the following rxn:?

Question

4Co3+ + 2H2O <--> 4Co2+ +02 + 4H+

Answer 1

The half reactions and the standard electrode potentials are

1: Co³⁺ + e⁻ ←→ Co²⁺ , E₁° = +1.81V

2: O₂ + 4H⁺ + 4e⁻ ←→ 2H₂O , E₂° = +1.23

Overall reaction is 4 times reaction 1 plus reaction 2 reverse. Hence the cell potential of the reaction is:

E° = 4∙E₁° - E₂° = 4∙1.81V - 1.23V = 6.01V

Cell potential is related to Gibbs energy of reaction by:

ΔG = -z∙F∙E°

(z number od electrons exchanged, F Faraday&#039;s constant)

For this reaction

ΔG = -4 ∙ 96485C/mol ∙ 5.46V = 2.32·10³J/mol

Equilibrium constant to ΔG by:

ΔG = -R∙T∙ln(K)

&lt;=&gt;

K = exp{-ΔG/(R∙T)}

(R gas constant, T absolute Temperature)

At standard temperature of 298.15K for our reaction

K = exp{-2.32·10³ / (8.314472J/molK ∙ 298.15K)} = 2.55