Chapter 25: Q. 3 (page 686)
Why is a high supporting electrolyte concentration used in most electroanalytical procedures?
To reduce the effect of moving electroactive spaces caused by electrostatic attraction, So we use high supporting electrolyte.
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What is the purpose of the electrodeposition step in stripping analysis?
A new method for determining ultrasmall () volumes by anodic stripping voltammetry has been proposed (W. R. Vandaveer and I. Fritsch, Anal. Chem.). In this method, a metal is exhaustively deposited from the small volume to be measured onto an electrode, from which it is later stripped. The solution volume is related to the total charge required to strip the metal by
where is the number of moles of electrons per mole of analyte, is the faraday, and is the molar concentration of the metal ion before electrolysis.
() Beginning with Faradayโs law (see Equation ), derive the above equation for .
() In one experiment, the metal deposited was from a solution that was in . The solution was electrolyzed for min at a potential of versus a gold top layer as a pseudo reference. A tubular nano band electrode was used. The silver was then anodically stripped off the electrode using a linear-sweep rate of . The following table represents idealized anodic stripping results. By integration, determine the total charge required to strip the silver from the tubular electrode. You can do a manual Simpsonโs rule integration or do the integration with Excel From the charge, determine the volume of the solution from which the silver was deposited.
() Suggest experiments to show whether all the was reduced to in the deposition step.
() Would it matter if the droplet were not a hemisphere? Why or why not?
() Describe an alternative method against which you might test the proposed method.
Why is a high supporting electrolyte concentration used in most electroanalytical procedures?
A solution containing was analyzed voltammetrically using the standard addition method. Twenty-five milliliters of the deaerated solution, which was in , produced a net limiting current of } at a rotating mercury film working electrode at a potential of (versus ). Following addition of of a standard solution, the resulting solution produced a current of }. Calculate the concentration of the sample.
What is the purpose of the electrodeposition step in stripping analysis?
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