Electroanalytical Methods Flashcards
In most electro analytical methods, it’s either a measure of _____ or _____
Current, potential
Measured in an electrochemical cell at a fixed potential
Current
Measured while the current is fixed at some constant values or zero
Potential
Electro analytical can be ____ and ____
Interfacial and bulk methods
Interfacing methods are of two types. ____ use potentiometric measurements while _____ measure other variables while the cell pitential is controlled
Static, dynamic
Potential of an electrochemical cell is measured under ____ conditions in a potentiometric analysis
Static
An electrode whose potential remains constant and against which other potentials can be measured
Reference electrode (anode)
Electrode whose potential is a function of the Concentra of analyte
Indicator electrode (cathode)
Reference electrode that consists of a Pt wire nthat is connected to a Pt surface in contact with an aqueous solution containing 1M H+ in equilibrium with H2 gas at a pressure of 1 atm
Standard Hydrogen Electrode (SHE)
Reference electrode that consists small amount of Hg mixed with some solid HgCl2, solid KCl, and enough saturated KCl solution to moisten the mixture
Saturated Calomel electrode
Reference electrode that functions as redox electrode and the equilibrium is between Ag and AgCl
Ag/AgCl electrode
Metallic and ion-selective electrodes (membrane electrodes) are types of _____
Indicator electrodes
Types of metallic electrode where in metals including Ag, Cu, Hg, Pb, Zn can serve as an indication for their own
Electrode of the first kind
Types of metallic electrode where in metal in contact with slightly soluble precipitate involving the metal cation; the electrode responds to anion concentration
Electrode of the second kind
Types of metallic electrode where in an inert electrode (Pt and Au) that serves as a source or sink for electrons for a redox half- reaction
Redox electrode
Electrode made of doped glass membrane sensitive to soecific ion. Used in pH meters.
Glass ion-selective electrode
An ion-selective electrode based on sparingly soluble inorganic crystalline material
Solid-state ion-selective electrode
An ion-selective electrode in which chelating agent is incorporated into a hydrophobic membrane
Liquid-based ion-selective electrode
An ion-selective electrode in which chelating agent is incorporated into a hydrophobic membrane
Liquid-based ion-selective electrode
An ion-selective electrode that responds to the concentration of a dissolved gas
Gas-sensing electrode
Measure of the response of an ion-selective electrode to other ions
Selectivity coefficient
Consist of a tube within a tube, the inner one housing the pH indicator electrode and the outer one housing the reference electrode and it’s salt bridge
Combination pH-reference electrode
Common reference electrode used in combination pH electrodes
Ag/AgCl electrode
In a cell, when the current is present, two additional phenomena must be considered which is ____ and ____
IR drop, polarization
An electrode phenomenon that may affect either or both of the electrodes in a cell.
Polarization
Polarization phenomena can be divided into two categories. Which one occurs because of the finite rate of mass transfer from the solution to the electrode surface
Concentra polarization
Movement of material from one location to another in three mechanisms: convection, migration, diffusion
Mass transfer
Results from mechanical motion of the solution as a result of stirring, vibration, or temperature differences
Convection
Movement resulting from stirring, vibration, or temperature differences
Convection
Movement of ions brought about by electrostatic attraction between the ions and the electrode of the opposite charge
Migration
Motion of species caused by a concentration gradient
Diffusion
The higher the current the largegr the concentration gradient until the surface concentration falls to zero wherein the max possible current called ___ is obtained.
Limiting current
Electro analytical method that involve measuring the quantity of electricity needed to convert the analyte quantitatively to a different oxidation state
Coulometry
The end point is determined _____ in volumetric procedure, whereas in the coulometric method, the end point is determined _____.
Potentiometrically, electrochemically
Uses volumetric or coulometric titration to determine trace amounts of water in a sample
Karl Fischer Titration
Group of methods in which information about the analyte is obtained by measuring current as a function of applied potential under conditions where concentration polarization exists
Voltammetry
Resulting plot of currenta against applied potential
Voltammogram
Electrode whuch the analyte is oxidized or reduced is called ____
Working electrode
Current plateau at top of voltammetric wave is called ____
Limiting current
Form of voltammetry that uses dropping mercury electrode
Polarography
Most efficient profile for voltammetry that applies a square wave superimposed on a staircase voltage ramp
Square Wave Polarography
Form of voltammetry in which the solution is mechanically stirred
Hydrodynamic voltammetry
Form of voltammetry in which a fixed potential range is employed where the voltage is scanned from a lower limit to an upper limit
Linear Sweep Voltammetry (LSV)
Form of Voltammetry where the voltage is swept between two values at a fixed rate. But when the voltage reaches the higehr limit, the scan is reversed and the voltage is swept back to the lower limit
Cyclic voltammetry
Form of voltammetry in which the analyte is first deposited on the electrode and the stripped
Stripped voltammetry (anodic, cathodic, and adsorptive)
