chapter 15/17

Question 1

Reference electrode

Answer 1

One that maintains a constant potential against which the potential of another half-cell may be measured.

Question 2

Indicator electrode

Answer 2

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.

Question 3

Working electrode

Answer 3

One at which the reaction of interest occurs. Same as indicator electrode.

Question 4

Sensing electrode

Answer 4

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.

Question 5

Junction potential

Answer 5

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.

Question 6

Anodic/cathodic peak potential

Answer 6

(Epc or Epa) The peaks on a cyclic voltammetry graph (head and feet of the duck) and the cathodic peak comes first.

Question 7

Selectivity Coefficient

Answer 7

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.

Question 8

Anodic/cathodic peak currents

Answer 8

(ipc and ipa) The distance from the middle of the duck to the peaks of either the anodic or cathodic peak potentials

Question 9

Potentiometry

Answer 9

An analytical method in which an electric potential difference (a voltage) of a cell is measured.

Question 10

Coulometry

Answer 10

A technique in which the quantity of analyte is determined by measuring the number of coulombs needed for complete electrolysis.

Question 11

coulometric titration

Answer 11

An electrolytic titration conducted with a constant current for a measured time

Question 12

Electrogravimetry

Answer 12

Analyte is quantitatively deposited on an electrode by electrolysis, whose increase in mass is them measured.

Electrochemical AND Mass measurement

Question 13

Amperometry

Answer 13

Measurement of electric current for analytical purposes.

Question 14

Voltammetry

Answer 14

An analytical method in which the relation between current and voltage is observed during an electrochemical reaction.

Question 15

Counter electrode

Answer 15

Current-carrying partner of the working electrode in an electrolysis. Also called auxillary electrode.

Question 16

Stripping Voltammetry

Answer 16

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)

Question 17

Polarography

Answer 17

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

Question 18

IR drop

Answer 18

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

Question 19

How is IR drop minimized?

Answer 19

1) having a small cell resistance
2) using a 3 electrode cell

Question 20

“ohmic response”

Answer 20

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

Question 21

Polarization

Answer 21

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.)

Question 22

Overpotential

Answer 22

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)

Question 23

ohmic potential

Answer 23

the voltage needed to overcome electric resistance of the solution in the electrochemical cell when a current is flowing.