Extracting Parameters from Microdisc Chronoamperometry

A lOmM aqueous solution of hydrazine, N2H4, was studied in pH 4.8 acetate buffer using a platinum microdisc electrode of radius 13.8 fim. Chronoamper-ometric transients were recorded in which the potential was stepped from a value corresponding to no current flow to one corresponding to the transport-limited current for the oxidation of N2H4. The following short-time data were recorded  

At long times a steady-state current of 1.96 x 10 A was measured. Calculate the number of electrons transferred in the oxidation of hydrazine. 

Since the concentration of the hydrazine is known to be 10 mM, the current-time data and the steady-state current allow us to find two unknowns, namely n, the number of electrons transferred in the oxidation, and D, the diffusion coefficient 0fN2H4. 

Note this plot is not expected to go through the origin, because of the decay to a constant value at a microelectrode, although the slope will be Cottrellian at short enough times. The limiting current value is not small enough compared to the current values reported in the table of data for the intercept of a Cottrell plot to be near zero. 

A graph of Ivst 2 shows a straight line of gradient 3.95 x 10 A S2. Therefore 

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