ELECTROGRAVIMETRY AND COULOMETRY PDF

Professor and Charles A. Dana Professor Chemistry and Biochemistry at Bates College No headers Electrodeposition or electrogravimetry are two terms used to describe the same analysis method. The general procedure is to use something like a platinum electrode and apply a constant reducing potential that is sufficient to plate out a solid metal. For example, this method could be used to plate out cadmium metal from solution by the reaction shown below. The difference in weight is solid cadmium and this amount can be related back to the concentration of cadmium in the original solution.

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Professor and Charles A. Dana Professor Chemistry and Biochemistry at Bates College No headers Electrodeposition or electrogravimetry are two terms used to describe the same analysis method. The general procedure is to use something like a platinum electrode and apply a constant reducing potential that is sufficient to plate out a solid metal.

For example, this method could be used to plate out cadmium metal from solution by the reaction shown below. The difference in weight is solid cadmium and this amount can be related back to the concentration of cadmium in the original solution.

Calculate potential values relative to a standard hydrogen electrode. Solution The first thing to consider is the two relevant half reactions for the metal ions in this problem. This means that it may be possible to apply a reducing potential that is sufficient to plate out cadmium but not large enough to plate out any of the iron.

The next step is to focus on the plating of cadmium. We only need to consider the half reaction for cadmium for this calculation. As the cadmium plates out, the concentration will be lower than 0. That would mean that only 0. The question we now need to answer is whether the potential needed to plate out The iron will plate out as well and interfere with the method. Is it possible to plate out Setting the potential somewhere in the window between — 0.

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Coulometry

It consists of two independent electrode circuits that are connected with a common electrode. For the better results, three electrode systems re used. Working electrode: used for the deposition of the sample. Counter electrode: used as a current sink. Reference electrode: maintains the fixed potential despite the changes in solution components. Constant potential electrogravimeter Electrode Used in the Electrogravimetry The electrode used in the electrogravimetry should posses the following characters: It should be non-reactive.

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7.2: Electrodeposition (Electrogravimetry)

Dynamic techniques, in which current passes through the electrochemical cell, also are important electrochemical methods of analysis. In this section we consider coulometry. Voltammetry and amperometry are covered in section 11D. Coulometry is based on an exhaustive electrolysis of the analyte. By exhaustive we mean that the analyte is completely oxidized or reduced at the working electrode or that it reacts completely with a reagent generated at the working electrode. There are two forms of coulometry: controlled-potential coulometry, in which we apply a constant potential to the electrochemical cell, and controlled-current coulometry, in which we pass a constant current through the electrochemical cell. Knowing the total charge, we then use equation

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