Cyclic Voltammetry

  • Thread starter zeromaxxx
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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...
 

Answers and Replies

  • #2
Borek
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What units ipc should be in? mA or A?
 
  • #3
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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?
 
  • #4
Borek
Mentor
28,628
3,102
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.
 
  • #5
Borek
Mentor
28,628
3,102
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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