Redox, Electrolysis and Related Concepts (Lecture Notes)

Vocabulary flashcards covering redox concepts, electrolysis, electrodes, and related terms.

Redox reaction

A reaction in which oxidation and reduction occur simultaneously.

Oxidation

Loss of electrons; increase in oxidation state; often associated with gain of oxygen.

Reduction

Gain of electrons; decrease in oxidation state; often associated with loss of oxygen.

Oxidation state (oxidation number)

A formal charge assigned to an atom representing electrons gained, lost, or shared in forming a compound.

Oxidation agent (oxidant)

The substance that causes another substance to be oxidized; itself reduced.

Reducing agent (reductant)

The substance that causes another substance to be reduced; itself oxidized.

Half-reaction

One of the two parts of a redox process showing either oxidation or reduction separately.

Spectator ion

An ion that does not change oxidation state during a redox reaction and does not participate in the electron transfer.

Oxidation half-reaction

Oxidation example: H2 → 2H+ + 2e− (loss of electrons).

Reduction half-reaction

Reduction example: Cu2+ + 2e− → Cu (gain of electrons).

Electrolysis

Decomposition of a compound by passing electric current through it, usually molten or in aqueous solution, using electrodes.

Electrolyte

A substance that contains mobile ions and conducts electricity when molten or in solution.

Cathode

The electrode at which reduction occurs; in electrolysis, it is the negative electrode.

Anode

The electrode at which oxidation occurs; in electrolysis, it is the positive electrode.

Inert electrode

An electrode that does not participate chemically in the reaction (e.g., graphite, platinum).

Active electrode

An electrode that participates in the chemical reaction (e.g., a metal that dissolves or deposits).

Deposition

The process by which a reduced metal ions plates onto the cathode.

Dissolution

The process by which electrode material loses electrons and goes into solution as ions.

Hydrogen evolution reaction

Cathodic reduction of H+ (or water) to form H2 gas.

Oxygen evolution reaction

Anodic oxidation of OH− (or water) to form O2 gas.

Conductivity

Ability of a substance to conduct electricity due to mobile ions in solution or delocalized electrons in metals.

OIL/RIG mnemonic

OIL = oxidation is loss; RIG = reduction is gain.

Activity series (reactivity series)

A ranking of metals by tendency to lose electrons; more reactive metals displace less reactive ones from compounds.

Galvanic cell vs. electrolytic cell

Galvanic: spontaneous, anode negative and cathode positive; Electrolytic: non-spontaneous, anode positive and cathode negative; both use ion transfer and electrodes.