# Cyclic Voltammetry

## 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

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...

Borek
Mentor
What units ipc should be in? mA or A?

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
Mentor
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
Mentor
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.