chapter 15/17 Flashcards
(23 cards)
Reference electrode
One that maintains a constant potential against which the potential of another half-cell may be measured.
Indicator electrode
One that develops a potential whose magnitude depends on the activity of one or more species in contact with the electrode. Same as working electrode.
Working electrode
One at which the reaction of interest occurs. Same as indicator electrode.
Sensing electrode
An electrode in which a gas-permeable membrane separates the test solution fluid from an aqueous electrode solution in contact with an ion-selective electrode.
Junction potential
An electric potential that exists at the junction (interface) between two different electrolyte solutions or substances. It arises in solutions as a result of unequal rates of diffusion of different ions.
Anodic/cathodic peak potential
(Epc or Epa) The peaks on a cyclic voltammetry graph (head and feet of the duck) and the cathodic peak comes first.
Selectivity Coefficient
With respect to an ion-selective electrode, a measure of the relative response of the electrode to two different ions. In ion-exchange chromatography, the selectivity coefficient is the equilibrium constant for displacement of one ion by another from the resin.
Anodic/cathodic peak currents
(ipc and ipa) The distance from the middle of the duck to the peaks of either the anodic or cathodic peak potentials
Potentiometry
An analytical method in which an electric potential difference (a voltage) of a cell is measured.
Coulometry
A technique in which the quantity of analyte is determined by measuring the number of coulombs needed for complete electrolysis.
coulometric titration
An electrolytic titration conducted with a constant current for a measured time
Electrogravimetry
Analyte is quantitatively deposited on an electrode by electrolysis, whose increase in mass is them measured.
Electrochemical AND Mass measurement
Amperometry
Measurement of electric current for analytical purposes.
Voltammetry
An analytical method in which the relation between current and voltage is observed during an electrochemical reaction.
Counter electrode
Current-carrying partner of the working electrode in an electrolysis. Also called auxillary electrode.
Stripping Voltammetry
Involves preconcentration of an analyte on an electrode, followed by a sweep to selectively oxidize or reduce the analyte
(The current generated is proportional to the amount of analyte present on the electrode)
Polarography
a voltammetric technique in which ions or molecules undergo oxidation or reduction at the surface of a dropping mercury electrode (DME) at an applied potential
Results in a linear voltage pattern
IR drop
resistance encountered when charge has to flow between a liquid gap or across a salt bridge. Can be considered as a drop in ohmic potential.
Eapplied=Ecell-IR
How is IR drop minimized?
1) having a small cell resistance
2) using a 3 electrode cell
“ohmic response”
a low resistance junction that provides current conduction from metal to semiconductor and vice versa.
Theoretically speaking the current should increase/ decrease linearly with the applied voltage
Polarization
occurs when you have an uneven distribution of things (charge, magnetic flux, ions, etc.)
Two Forms: Concentration Polarization (difference in bulk and surface concentrations) and Kinetic Polarization (current limited by electron transfer rate between the electrode surfaces and the reactants in the solution.)
Overpotential
the voltage required to overcome the activation energy for a reaction at an electrode
(if you want the reaction to happen faster then you need a greater overpotential)
ohmic potential
the voltage needed to overcome electric resistance of the solution in the electrochemical cell when a current is flowing.
