Oxidation- The addition of oxygen, removal of electrons, or increase in oxidation number of a substance.

Reduction- The removal of oxygen, addition of electrons, or decrease in oxidation number of a substance.

Redox Reaction- A reaction in which oxidation and reduction take place at the same time.

OIL RIG- Oxidation Is Loss of electrons, Reduction Is Gain of electrons.

Half-equation- in a redox reaction, an equation showing either an oxidation or a reduction.

Oxidation Number (Oxidation State)- A number given to an atom in a compound that describes how oxidized or reduced it is.

Oxidizing Agent- A reactant that increases the oxidation number of (or removes electrons from) another reactant.

Reducing Agent- A reactant that decreases the oxidation number of (or adds electrons to) another reactant.

(Chapter 20)

Electrolysis- The decomposition of a compound into its elements by an electric current.

Electrolyte- A molten ionic compound or an aqueous solution of ions that is decomposed during electrolysis.

Electrode- A rod of metal or carbon (graphite) which conducts electricity to or from an electrolyte.

Anode- The positive electrode.

Cathode- The negative electrode.

Cation- A positively charged ion.

Anion- A negatively charged ion.

Faraday (Constant)- The charge carried by 1 mole of electrons (or 1 mole of charged ions); it has a value of 96,500 coulombs per mole (C/mol).

Electrode Potential (E)- The voltage measured for a half cell compared with another half cell.

Standard Hydrogen Electrode- A half-cell in which hydrogen gas at a pressure of 1 atmosphere (101kPa) bubbles into a solution of 1.00 mol/dm[superscript -3] H+ ions; This electrode is given a standard electrode potential of 0.00V; All other standard electrode potentials are measured relative to this value.

Half Cell- Half of an electrochemical cell; the half cell with the more negative E[superscript naught] value supplies electrons, the half cell with the more positive E[superscript naught] value receives electrons.

Electrochemical Cell- Two half cells soaked in potassium nitrate solution joined by a salt bridge; when the poles of the half cells are joined by a wire, electrons travel in the external circuit from the half cell with the more negative E[superscript naught] value to the half cell with the more positive E[superscript naught] value.

Salt Bridge- A piece of filter paper soaked in potassium nitrate solutions used to make electrical contact between the half cells in an electrochemical cell.

Standard Electrode Potential- The electrode potential of a half cell when measured with a standard hydrogen electrode as the other half cell, denoted (E[superscript naught]).

Standard Cell Potential- The difference in standard electrode potential between two half cells.

Feasibility (of Reaction)- The likelihood or not of a reaction occurring when reactants are mixed; we can use E[superscript naught] values to assess the feasibility of a reaction.

Nernst Equation- An equation used to predict qualitatively how the value of an electrode potential varies with the concentration of aqueous ions; E=E[superscript naught] + (RT/zF)*ln([oxidized form/reduced form]).

Fuel Cell- A source of electrical energy that comes directly from the energy stored in the chemicals of the cell, one of which is oxygen (which may come from the air).

Discharge- The conversion of ions to atoms or molecules at electrodes during electrolysis, for example, during the electrolysis of sodium chloride solution, chlorine is discharged at the anode by the conversion of Cl- ions to Cl atoms, which then combine to for Cl2 molecules.