Cyclic Voltammetry

[zeromaxxx]

1. The problem statement, all variables and given/known data

Calculate the diffusion coefficient (cm2/s) of ferricyanide if cyclic voltammograms conducted on a solution of 1 mM KClO4 + 5 mM K4Fe(CN)6 at scan rates of 1, 2, 5, 10, 20, and 50 mV/s, resulted in peak currents of 76, 100, 175, 243, 348 and 552 mA. The electrode used for the experiment had been modified with a polymeric coating an effective area of 0.56 cm2.

2. Relevant equations

ipc=(269000)n3/2AD1/2C v1/2

A=0.56 cm2
n=1
C= 0.000005 mol/cm3

3. The attempt at a solution

I ploted the ipc vs. v1/2 and found the slope of the line which was approx. 76.747

ipc/v1/2 = 76.747

Isolating for D =[76.747/((269000)n3/2AC)]2

=[76.747/((269000)13/20.56x0.000005)]2

= 10 382.51

which is clearly wrong since the theoretical value of D is 7.6 x 10-6

Can anyone point out my mistake? I have a feeling it's with the concentration though I'm not quite sure...

[Borek]

What units ipc should be in? mA or A?

[zeromaxxx]

What units ipc should be in? mA or A?

it should be A but does that make a difference when the slope is calculated? since v1/2 is in mV/s and the slope would pretty much amount to the same value of 76.747?

[Borek]

it should be A but does that make a difference when the slope is calculated? since v1/2 is in mV/s and the slope would pretty much amount to the same value of 76.747?

That's not how it works.

[Borek]

it should be A but does that make a difference when the slope is calculated? since v1/2 is in mV/s and the slope would pretty much amount to the same value of 76.747?

That's not how it works.