Lecture 14: Electrochemistry Flashcards
Define electrochemistry
Measurement of current or voltage in an electrochemical cell; consists of >2 electrodes that interact with a chemical and that are connected to an electrical system.
What happens to chemical energy within electrochemistry?
It is converted to an electrical current, or flow of electrons, in a galvanic cell.
Define galvanic cell
Two half cells (i.e. anode and cathode) with each containing a metal in a solution of one of its salts.
Characteristics of an Anode
(1) Positive pole
(2) Oxidation reaction
(3) Loss of electrons
Characteristics of a Cathode
(1) Negative pole
(2) Reduction reaction
(3) Gain of electrons
Within a galvanic cell, how do electrons flow?
From the anode to the cathode
What are some examples of what electrochemistry is used to measure?
(1) Ions; (2) Drugs; (3) Hormones; (4) Metals; (5) Gases
Define Potentiometry
Technique in which the electrical potential difference between two electrodes is measured under equilibrium.
Difference is measured using a voltage or pH meter.
Define Potentiometric Sensors
Measures electrical potential differences between two electrodes or half-cells in an electrochemical cell.
Commonly used to measure pH, pCO2, and electrolytes.
In potentiometry, what are the two half cells?
An indicator electrode and a reference electrode.
In potentiometry, what is the indicator electrode used for?
The main component, selectively responds to the analyte of interest.
Ion Selective Electrode (ISE)
In potentiometry, what is the reference electrode used for?
Used as a fixed reference for the cell potential measurements.
ISE’s are selectively permeable to certain ions, what are they?
H+, K+, Na+, and Mg2+
What type of ISE membrane is most common in chemistry analyzers?
Polymer membrane
What type of ISE membrane is most common in pH electrodes?
Glass membrane because it permits the passage of H+ ions.
Define amperometry
Measures current flowing through an electrochemical cell and the electrochemical potential between the two electrodes while a constant external voltage is applied.
What is a Clark electrode?
A type of electrode used for pO2 readings.
Define conductometry
The measurement of electrolytic conductivity to monitor the progress of a chemical reaction.
In conductometry, how is the current related to the concentration of ions?
The current is proportional the the concentrations of ions.
Define coulometry
Measures the amount of charge (in coulombs) passing between two electrodes at a fixed potential (based on amperometry) as a result of a chemical reaction.
