Chapter 19: Electrochemistry Flashcards

Vocabulary terms and definitions from Chapter 19 covering redox reactions, galvanic cells, standard potentials, and electrolysis.

Reduction-oxidation (redox) reactions

Reactions in which electrons are transferred from one species to another, resulting in changes in oxidation states.

Reduction

The gain of electrons, which results in a decrease in the oxidation number.

Oxidation

The loss of electrons, which results in an increase in the oxidation number.

Half-reaction method

A procedure for balancing complicated redox equations by separating the reaction into two parts: oxidation and reduction.

Galvanic cell

An apparatus for generating electricity through the use of a spontaneous chemical reaction.

Half-cell

The individual container in a galvanic cell where either an oxidation or reduction half-reaction occurs.

Anode

The electrode at which oxidation occurs; in a galvanic cell, electrons flow from this electrode.

Cathode

The electrode at which reduction occurs; in a galvanic cell, electrons flow to this electrode.

Salt bridge

A conducting medium containing cations and anions that connects two half-cells, completing the circuit to allow electrons to flow through an external wire.

Cell potential ($E_{cell}$)

The difference in electrical potential between the anode and the cathode, measured in volts ($V$).

Standard hydrogen electrode (SHE)

A reference electrode at $25^\circ C$ where hydrogen gas at $1\,atm$ is bubbled into a $1\,M$ $HCl$ solution, with a defined potential of exactly $0.0\,V$.

Standard reduction potential ($E^\circ$)

The voltage associated with a reduction half-reaction at standard-state conditions ($1\,M$ for dissolved species and $1\,atm$ for gases).

Faraday's constant ($F$)

A constant representing the quantity of electric charge per mole of electrons, equal to $96485\,C/mol\,e^-$.

Coulomb ($C$)

A unit of electric charge; one Coulomb is the amount of charge transferred by a current of one ampere in one second.

Equilibrium constant ($K$)

A value related to the spontaneity of a reaction; in a spontaneous redox reaction, $K$ is typically greater than 1.

Electrolysis

The use of electrical energy to drive a nonspontaneous chemical reaction.

Electrolytic cell

An electrochemical cell specifically used to carry out electrolysis using an external voltage source.

Ampere ($A$)

A unit of electric current defined as one Coulomb per second ($C/s$).

Corrosion

The spontaneous and often undesired oxidation of metals when exposed to oxidizing agents in the environment.

Galvanized iron

Iron coated with zinc; because zinc is more easily oxidized than iron, it serves as a protective coating that prevents the iron from rusting.

Sacrificial electrode

A metal placed in contact with iron that oxidizes more easily than the iron, thereby protecting the iron from corrosion.