Glossary
Anode
The electrode in an electrochemical cell where oxidation occurs, meaning electrons are lost.
Example:
In a galvanic cell, zinc metal often acts as the anode, losing electrons to become Zn²⁺ ions.
Cathode
The electrode in an electrochemical cell where reduction occurs, meaning electrons are gained.
Example:
In a copper-silver cell, silver ions gain electrons at the cathode to form solid silver.
Cell potential
The driving force that pushes electrons through an electrochemical circuit, indicating the spontaneity of a redox reaction.
Example:
A voltaic cell with a high cell potential of +2.0 V will spontaneously generate a strong electrical current.
Electromotive force (EMF)
Another name for cell potential, representing the maximum potential difference between two electrodes in an electrochemical cell.
Example:
The electromotive force of a standard AA battery is typically around 1.5 volts.
Equilibrium Constant (K)
A value that expresses the ratio of products to reactants at equilibrium for a reversible reaction, indicating the extent to which the reaction proceeds.
Example:
A very large equilibrium constant suggests that a reaction strongly favors the formation of products at equilibrium.
Faraday's constant
The charge carried by one mole of electrons, approximately 96,485 coulombs per mole of electrons.
Example:
Faraday's constant is essential for converting between electrical charge and moles of electrons transferred in electrochemical calculations.
Gibbs Free Energy change (ΔG°)
A thermodynamic quantity that indicates the maximum reversible work that can be performed by a system at constant temperature and pressure, and its sign determines spontaneity.
Example:
A negative Gibbs Free Energy change for a reaction confirms it is spontaneous and can proceed without external energy input.
Oxidation
A chemical process involving the loss of electrons by a species, resulting in an increase in its oxidation state.
Example:
When iron rusts, the iron metal undergoes oxidation, losing electrons to form iron oxides.
Reduction
A chemical process involving the gain of electrons by a species, resulting in a decrease in its oxidation state.
Example:
In a battery, lithium ions undergo reduction as they gain electrons and are incorporated into the electrode material.
Standard cell potential (E°cell)
The cell potential measured under standard conditions (1 M concentration for solutions, 1 atm pressure for gases, 298 K temperature).
Example:
Calculating the standard cell potential helps predict if a redox reaction will be spontaneous under ideal laboratory conditions.
Standard reduction potential
The potential of a half-reaction to undergo reduction relative to the standard hydrogen electrode (SHE), measured under standard conditions.
Example:
A high positive standard reduction potential for a species indicates it is a strong oxidizing agent, readily accepting electrons.