electrochemistry (pg. 2&3)

auxiliary oxidizing and reducing agents

reagents that are added to the analyte to convert it to its single oxidation state so that the reagents can react appropriately

auxiliary oxidizing and reducing agents

these are used with some samples that are usually in a complex oxidation state

auxiliary oxidizing and reducing agents

Like iron-containing samples that usually contains a mixture of iron (II) and iron (III), and so we add an auxiliary agent to convert all the iron into iron (II) only

auxiliary oxidizing and reducing agents

to be a useful preoxidant/prereductant, the reagent must react quantitatively with the analyte

auxiliary oxidizing and reducing agents

must be readily removable because excess reagent usually interferes by reaction with the standard solution

auxiliary oxidizing and reducing agents

a number of metals are good reducing agents and have been used for the prereduction of analytes

zinc, aluminum, cadmium, lead, nickel, copper, silver

what are the some examples of metals that are good reducing agents which have been used in prereduction of analytes?

sodium bismuthate

A powerful oxidizing agent that is capable of converting manganese (II) to permanganate ion

redox reactions in electrochemical cells

the oxidizing agent and the reducing agent are physically separated from one another

cell potential

is a measure of tendency of the cell reaction to proceed toward equilibrium

redox reactions in electrochemical cells

the cell potential is a measure of tendency of the cell reaction to proceed toward equilibrium

standard hydrogen reference electrode

has been used as a universal reference electrode

standard hydrogen reference electrode

a typical gas electrode

standard hydrogen reference electrode

detects changes in electric charge

potentiometry

the measurement of the differences of the two half-cells in a voltage at a constant current

potentiometry

shown by the Nernst Equation

ion selective electrode

most common application of potentiometry is the ???

ph electrode

is an ISE universally used in the clinical laboratory specifically to determine electrolytes

ion selective electrode

Has an indicator electrode and a reference electrode and the voltameter will determine the change in voltage at a constant current

indicator electrode

for sodium determination, the indicator electrode is a glass membrane

indicator electrode

for potassium determination, the indicator electrode is valinomycin

glass memebrane

for sodium determination what is the indicator electrode?

valinomycin

for potassium determination what is the indicator electrode?

ph electrode

are highly selective for Ht, however, other cations in high concentrations can interfere in glass membranes

sodium

in indicator or ph electrode what is the most common interference?

reference electrode

basis or reference if equilibrium has been reached

reference electrode

the calomel electrode is commonly used

calomel

is a paste of predominantly mercurous chloride

calomel electrode

It is in direct contact with metallic mercury in an electrolyte solution of potassium chloride

ag/agcl

is another common reference electrode

ag/agcl

Can be used at temperatures as high as 275C

ag/agcl

Are also less toxic than mercury

mercury sulfate and potassium sulfate

can also be used to avoid chloride contamination

liquid junction

found at the lowest portion of the reference electrode

liquid junction

electrical connection between the indicator and reference electrodes

liquid junction

achieved by allowing a slow flow of electrolyte from the tip of the reference electrode

kcl

is a commonly used filling solution

readout meter

zero potential for the cell indicates that each electrode half-cell is generating the same voltage, assuming there in no liquid junction potential

isopotential

is the potential at which a temperature change has no effect on the response of the electrical cell

polarography

the measurement of difference in current at a constant voltage

polarography

may be used to measure trace metals, oxygen, vitamin C, and amino acids concentration

polarography

the relationship between the differences in current and voltage is shown by the Ilkovic equation

ilkovic equation

the relationship between the differences in current and voltage is shown by the ????

coulometry

electricity is expressed in terms of Coulombs (C)

coulometry

measurement of the amount of electricity at a fixed potential

coulomb

is equal to a current flow of 1 ampere per second

coulometry

the relationship is expressed by Faraday's law

amperometry

the measurement of the amount of current that flows when a constant voltage is applied to the measuring electrode

amperometry

equivalence point is established by changes in average of current passing through a solution during progress of titration of the said current being under an applied constant voltage

conductometry

the measurement of the current flow between two non-polarizable electrodes between which is known electrical potential is established