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# Electrochemistry: Molecules in a Serotonin

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Hi,

Please include a stepwise solution for the questions attached regarding the number of molecules a serotonin produces given other variables.

Problem 6
A very small micro electrode, used to determine serotonin in a single brain cell is held for a period of 0.1 s at a potential positive enough to oxidise the analyte, (it is a 1e- transfer). If 0.5 pA of faradaic current is passed in this time, calculate the number of molecules of serotonin actually determined.

Problem 7
A cyclic voltammogram of a solution of a species (A) is obtained using a 25 urn diameter microelectrode. A • A* + 1e-Under transient conditions (at 4 Vs-') the peak current (in) is 57.8 nA, while under steady-state conditions (at 0.1 Vs-1) the limiting current (iL) is found to be 27.5 nA. Calculate the Diffusion coefficient (D) and the Concentration (c) of the species A in solution.

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#### Solution Preview

Please see the attachment.

Problem 6
According to Faraday's law, the charge is directly proportional to the amount of species undergoing a loss (oxidation) or gain (reduction) of electrons:
Q = n F e
where Q = total charge generated (in coulomb), n = number of moles of a species undergoing oxidation or reduction, F = Faraday's constant (96485 C/mol), and e = number of electrons per molecule lost or gained

Here, e = 1 and Q = current (ampere) x time (sec) = (0.5 x 10-12) x 0.1 coulomb

Thus, 0.5 x 10-12 x 0.1 = n x 96485 x 1
or n = (0.5 x 10-12 x 0.1) / 96485 = 5.18 x 10-7 x 10-12 = 5.18 x 10-19 moles

Now 1 mole of a ...

#### Solution Summary

This solution offers detailed step-wise calculations, in answer to two advanced electrochemistry problems.

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