Calculate Diffusion Coefficient K4Fe(CN)6 Cyclic Voltammetry

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The discussion focuses on calculating the diffusion coefficient of ferricyanide using cyclic voltammetry data. The user plotted peak current (ipc) against the square root of scan rate (v1/2) and derived a slope of approximately 76.747. They attempted to isolate the diffusion coefficient (D) using the equation provided but obtained a value significantly higher than the theoretical value. Questions arose regarding the appropriate units for ipc, whether to use mA or A, and how this choice affects the slope calculation. Clarifications on unit consistency and calculation methods are sought to resolve the discrepancy.
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Homework Statement



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.

Homework Equations



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

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

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...
 
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What units ipc should be in? mA or A?
 
Borek said:
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?
 
zeromaxxx said:
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.
 
zeromaxxx said:
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.
 

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