Calculating rate constants using, dG = -nFEo = -RTlnKc with, Kc = rate constant

Question

Calculating rate constants

using,

dG = -nFEo = -RTlnKc

with,

Kc = rate constant

R = gas constant

T = temperature = 298 K

n = number of electrons

F = Faraday's constant

Eo = Ecathode - Eanode

So,

[Cr(OH2)6]2+ oxidation with [Ru(NH3)6]3+

Eo = 0.07 - (- 0.41) = 0.48 V

So,

Kc = in.ln(1 x 96500 x 0.48/8.314 x 298) = 1.32 x 10^8

[Cr(OH2)6]2+ oxidation with [Fe(OH2)6]3+

Eo = 0.77 - (- 0.41) = 1.18 V

So,

Kc = in.ln(1 x 96500 x 1.18/8.314 x 298) = 9.13 x 10^19

[Cr(OH2)6]2+ oxidation with [Ru(bpy)3]3+

Eo = 1.26 - (- 0.41) = 1.67 V

So,

Kc = in.ln(1 x 96500 x 1.67/8.314 x 298) = 1.77 x 10^28

So as can be seen from the calculations, as the Eo value goes up, the magnitude of rate constant also increases.

Therefore, [Ru(bpy)3]3+ is the strongest oxidizing agent in this case.

Explanation / Answer

Rate constants of Electron Transfer (Inorganic)

21.21 Calculate the rate constants for electron transfer in the oxidation of [Cri OH,kE'ICr"Kr2"F-0.4 1V) and each of the Comment on the relative sizes of the rate constants

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