Electrochemistry Flashcards
the magnitude of a voltage or current signal originating from an electrochemical cell is related to the activity or concentration of a particular chemical species in the cell
Electrochemistry
involves the measurement of electrical signals associated with chemical system that are incorporated into an electrochemical cell
Electrochemistry
converts chemical energy into electrical energy.
Galvanic cell
are required to complete the circuit between the reference and without contaminating anything.
Liquid junction - also known as a salt bridge
Functions:
It allows electrical contact between the two solutions.
It prevents the mixing of the electrode solutions.
It maintains the electrical neutrality in each half cell as ions flow into and out of the salt bridge.
Liquid junction - also known as a salt bridge
Electrochemical Techniques
Potentiometry
Coulometry
Amperometry
Voltammetry
measurement of a potential or voltage difference between two electrodes immersed in solution under the condition of essentially zero current.
Potentiometry
the measured potential is related to the molar concentration by the____ equation
Potentiometry
Nernst
Potentiometry
ELECTRODES
- responds to changes in the activity of solution measuring electrode
b)Indicator Electrode
Reference Electrode
_____mercury/mercurous chloride
_____overall better and faster
_____
Calomel electrode
Silver/silver chloride
Normal hydrogen electrode
-indicator electrode that can respond to individual types of anions or cations
-very sensitive and selective for the ion it measures
Ion-selective electrode
2 types of Ion-selective electrode
(1) Direct ISE
(2) Indirect ISE
-its ionic selectivity depends on the membrane/barrier composition used
Ion-selective electrode
Ion selective electrodes
a. glass aluminum silicate (____)
b. valinomycin gel (____)
c. organic liquid membrane ion exchangers (_____)
d. gas and enzyme electrodes
Sodium
Potassium
Calcium and Lithium
selective for the detection of hydrogen
ions indicator electrode has a glass membrane
pH electrode
pH electrode
internal reference electrode
Ag/AgCl
pH electrode contained within a plastic jacket.
sodium buffer and permeable membrane (_____)
pCO2 electrode
Teflon silicone
The measurement of current after which a potential is applied to an electrochemical cell
Voltammetry
- for Lead and Iron Testing
Anodic stripping voltammetry
Three Electrodes for voltammetry
Working Electrode
Reference Electrode
Auxiliary Electrode
makes contact with the analyte facilitate the transfer of charge to and from the analyte
a)WORKING ELECTRODE
a half cell with a known reduction potential
b)REFERENCE ELECTRODE
to sustain electrolysis - process by which electric current is passed through a substance to effect a chemical change (substance loses or gains an electron)
c)AUXILIARY ELECTRODE
Coulometry
is an electrochemical titration in which the titrant is electrochemically generated and the endpoint is detected by______
amperometry
the time required to titrate a sample at a constant current is measured and is related to the amount of analyte in a sample by______
Coulometry
Faraday’s equation
Coulometry
Use:
Chloride test (CSF, serum and sweat)
is the measurement of the current flow produced by an oxidation–reduction reaction at a single applied potential
Amperometry
a measure of the cell current when the potential difference between indicator and reference electrodes is controlled
Amperometry
- uses a gas-permeable membrane, usually polypropylene, which allows dissolved oxygen to pass through
pO 2 gas-sensing electrode
Glucose electrode
Amperometry
measure potential (voltage) under zero current
Potentiometry
is an electrochemical titration in which the titrant is electrochemically generated and the endpoint is detected by amperometry; constant current
Coulometry
measure current after applying a potential
Voltammetry
measure current, controlled/constant potential (voltage)
Amperometry
Where oxidation takes place
Anode
Where reduction takes place
Cathode
_____reaction is spontaneous and is responsible for the production of electrical energy.
redox
The two______ are set up in different containers, being connected through the salt bridge or porous partition.
half-cells
Potentiometry
ELECTRODES
- Produces constant potential
a.) reference electrode
ISE
(Sodium)
glass aluminum silicate
ISE
(Potassium)
valinomycin gel
ISE
(Calcium and Lithium)
organic liquid membrane ion exchangers
Produces constant potential
Reference electrodes
