Chapter 17 Key Terms

active electrode

electrode that participates as a reactant or product in the oxidation-reduction reaction of an electrochemical cell; the mass of an active electrode changes during the oxidation-reduction reaction

alkaline battery

primary battery similar to a dry cell that uses an alkaline (often potassium hydroxide) electrolyte; designed to be an improved replacement for the dry cell, but with more energy storage and less electrolyte leakage than typical dry cell

anode

electrode in an electrochemical cell at which oxidation occurs

battery

single or series of galvanic cells designed for use as a source of electrical power

cathode

electrode in an electrochemical cell at which reduction occurs

cathodic protection

approach to preventing corrosion of a metal object by connecting it to a sacrificial anode composed of a more readily oxidized metal

cell notation (schematic)

symbolic representation of the components and reactions in an electrochemical cell

cell potential (E_cell)

difference in potential of the cathode and anode half-cells

combustion reaction

vigorous redox reaction producing significant amounts of energy in the form of heat and, sometimes, light

concentration cell

galvanic cell comprising half-cells of identical composition but for the concentration of one redox reactant or product

corrosion

degradation of metal via a natural electrochemical process

dry cell

primary battery, also called a zinc-carbon battery, based on the spontaneous oxidation of zinc by manganese(IV)

electrode potential (E_X)

the potential of a cell in which the half-cell of interest acts as a cathode when connected to the standard hydrogen electrode

electrolysis

process using electrical energy to cause a nonspontaneous process to occur

electrolytic cell

electrochemical cell in which an external source of electrical power is used to drive an otherwise nonspontaneous process

Faraday’s constant (F)

charge on 1 mol of electrons; F = 96,485 C/mol e⁻

fuel cell

devices similar to galvanic cells that require a continuous feed of redox reactants; also called a flow battery

galvanic (voltaic) cell

electrochemical cell in which a spontaneous redox reaction takes place; also called a voltaic cell

galvanization

method of protecting iron or similar metals from corrosion by coating with a thin layer of more easily oxidized zinc.

half cell

component of a cell that contains the redox conjugate pair (“couple”) of a single reactant

half-reaction

an equation that shows whether each reactant loses or gains electrons in a reaction.

inert electrode

electrode that conducts electrons to and from the reactants in a half-cell but that is not itself oxidized or reduced

lead acid battery

rechargeable battery commonly used in automobiles; it typically comprises six galvanic cells based on Pb half-reactions in acidic solution

lithium ion battery

widely used rechargeable battery commonly used in portable electronic devices, based on lithium ion transfer between the anode and cathode

Nernst equation

relating the potential of a redox system to its composition

nickel-cadmium battery

rechargeable battery based on Ni/Cd half-cells with applications similar to those of lithium ion batteries

oxidation

process in which an element’s oxidation number is increased by loss of electrons

oxidation number

(also, oxidation state) the charge each atom of an element would have in a compound if the compound were ionic

oxidation-reduction reaction

(also, redox reaction) reaction involving a change in oxidation number for one or more reactant elements

oxidizing agent

(also, oxidant) substance that brings about the oxidation of another substance, and in the process becomes reduced

primary cell

nonrechargeable battery, suitable for single use only

reducing agent

(also, reductant) substance that brings about the reduction of another substance, and in the process becomes oxidized

reduction

process in which an element’s oxidation number is decreased by gain of electrons

sacrificial anode

electrode constructed from an easily oxidized metal, often magnesium or zinc, used to prevent corrosion of metal objects via cathodic protection

salt bridge

tube filled with inert electrolyte solution

secondary cell

battery designed to allow recharging

single-displacement reaction

(also, replacement) redox reaction involving the oxidation of an elemental substance by an ionic species

standard cell potential (E°_cell​)

the cell potential when all reactants and products are in their standard states (1 bar or 1 atm or gases; 1 M for solutes), usually at 298.15 K

standard electrode potential (E°_X​)

electrode potential measured under standard conditions (1 bar or 1 atm for gases; 1 M for solutes) usually at 298.15 K

standard hydrogen electrode (SHE)

half-cell based on hydrogen ion production, assigned a potential of exactly 0 V under standard state conditions, used as the universal reference for measuring electrode potential