Reversibilidade Eletroquímica

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199Chapter 11 Electrochemical Methods
 A one-electron reduction for Ni2+ is not consistent with its reduction 
reaction of
( ) eaq 2 Ni(Hg)Ni2
?+
+ -
 Presumably there is a slow rate of electron transfer that prevents the 
reduction from displaying electrochemical reversibility.
39. To evaluate electrochemical reversibility for cyclic voltammetry we 
examine values for DEp, where DEp = Ep,a – Ep,c. For an electro-
chemically reversible reaction, DEp is independent of scan rate and 
equal to 0.05916/n. For p-phenyldiamine, DEp varies from 0.044 V 
at a scan rate of 2 mV/s to 0.117 V at a scan rate of 100 mV/s, all of 
which exceed the theoretical value of 0.05916/2 = 0.02953 V; thus, 
the reaction is not electrochemically reversible. For each scan rate, the 
ratio of the cathodic peak current and the anodic peak currents are 
approximately 1.00, which means the reaction must be chemically 
reversible; thus, the lack of electrochemical reversibility presumably 
results from slow kinetics and not from a chemical reaction.