Ch 20 Electrochemistry

Acidic

pH below 7

Basic

pH above 7

Anode

Electrode where oxidation of the entire cell occurs (electrons are produced by the cell and go out into the circuit). Inside the cell, electrons flow from the cathode to the anode.

Cathode

Electrode where reduction of the entire cell occurs (electrons go into the cell from the circuit). Inside the cell, electrons flow from the cathode to the anode.

Battery

A device that converts chemical energy to electrical energy.

Primary cell

Non-rechargeable battery

Lead-acid battery

A battery that runs on the oxidation of lead and the reduction of lead(IV) oxide in the presence of sulfuric acid.

Example: Car battery

Alkaline battery

Primary battery that uses an alkaline (often potassium hydroxide) electrolyte.

Example: Flashlight

Secondary cell

Rechargeable battery

Metal hydride battery

Secondary cell using a hydrogen-absorbing alloy

Example: Rechargeable flashlight

Li ion battery

Lithium cations flow within the cell. Examples: Cell phones, Electric vehicles (EVs).

Cell potential (Ecell)

The difference in electric potential between the cathode and the anode.

(AKA electromotive force)

Concentration cell

A galvanic cell in which both compartments contain the same components, but at different concentrations

Corrosion

The gradual wearing away of a metal element due to a chemical reaction

Cathodic protection

A method in which an active metal, such as magnesium, is connected to steel to protect it from corrosion

Coulomb

SI unit of electric charge

Electrochemistry

Study of chemical reactions involving electricity

Electrolysis

A process by which an electric current breaks chemical bonds.

Electrolytic cell

Cell that uses electrical energy to produce a chemical change that would otherwise not occur spontaneously

Electroplating

An electrolytic process in which a metal ion is reduced causing solid metal to be deposited on a surface

Faraday constant (F)

96,485 C/mol e-

The amount of charge in one mole of electrons.

Fuel cell

An electrical-chemical device that converts fuel, such as hydrogen, into an electrical current.

Half reaction

An equation showing either the oxidation or the reduction that takes place in a redox reaction.

Nernst equation

Ecell= E°cell - (RT/nF) (lnQ)

Used to calculate the potential of a non-standard voltaic cell.

Redox

A combination of reduction and oxidation reactions.

Oxidation

loss of electrons

Oxidation number (state)

Number that indicates how many electrons an atom has gained or lost.

Oxidizing agent (oxidant)

Oxidizes another chemical by accepting electrons, is reduced.

Reduction

gain of electrons

Reducing agent (reductant)

Reduces another chemical by giving it electrons, is oxidized.

Salt bridge

A tube that allows the slow transfer of ions and maintains the neutrality of the electrolyte solutions. Completes a voltaic circuit.

Standard reduction potential

The potential of a half-reaction under standard state conditions, as measured against the potential of the standard hydrogen electrode.

Standard Hydrogen Electrode (SHE)

The half-cell electrode that is chosen to have a potential of zero. Other half-cells are compared to this one.

Voltaic cell (galvanic cell)

A type of electrochemical cell that uses chemical reactions (chemical energy) to produce electrical energy (electricity)