Chapter 19 & 20

Question 0

cathode

Answer 0

An electrode at which reduction occurs. (Section 20.3)

Question 1

anode

Answer 1

An electrode at which oxidation occurs. (Section 20.3)

Question 2

cell potential

Answer 2

The potential difference between the cathode and anode in an electrochemical cell; it is measured in volts: 1 V

Question 3

concentration cell

Answer 3

A voltaic cell containing the same electrolyte and the same electrode materials in both the anode and cathode compartments. The emf of the cell is derived from a difference in the concentrations of the same electrolyte solutions in the compartments. (Section 20.6)

Question 4

electrochemistry

Answer 4

The branch of chemistry that deals with the relationships between electricity and chemical reactions. (Chapter 20: Introduction)

Question 5

electromotive force (emf)

Answer 5

A measure of the driving force, or electrical pressure, for the completion of an electrochemical reaction. Electromotive force is measured in volts: 1 V

Question 6

entropy

Answer 6

A thermodynamic function associated with the number of different equivalent energy states or spatial arrangements in which a system may be found. It is a thermodynamic state function, which means that once we specify the conditions for a system—that is, the temperature, pressure, and so on—the entropy is defined. (Section 19.2)

Question 7

Faraday’s constant (F)

Answer 7

The magnitude of charge of one mole of electrons: 96,500 C/mol. (Section 20.5)

Question 8

free energy (Gibbs free energy, G)

Answer 8

A thermodynamic state function that gives a criterion for spontaneous change in terms of enthalpy and entropy: G

Question 9

Gibbs free energy

Answer 9

A thermodynamic state function that combines enthalpy and entropy, in the form G

Question 10

half-reaction

Answer 10

An equation for either an oxidation or a reduction that explicitly shows the electrons involved, for example, Zn2+ (aq) + 2e– →Zn(s). (Section 20.2)

Question 11

irreversible process

Answer 11

A process that cannot be reversed to restore both the system and its surroundings to their original states. Any spontaneous process is irreversible. (Section 19.1)

Question 12

isothermal process

Answer 12

One that occurs at constant temperature. (Section 19.1)

Question 13

microstate

Answer 13

The state of a system at a particular instant; one of many possible energetically equivalent ways to arrange the components of a system to achieve a particular state. (Section 19.3)

Question 14

Nernst equation

Answer 14

An equation that relates the cell emf, E, to the standard emf, E°, and the reaction quotient, Q:E

Question 15

oxidizing agent, or oxidant

Answer 15

The substance that is reduced and thereby causes the oxidation of some other substance in an oxidation-reduction reaction. (Section 20.1)

Question 16

reducing agent, or reductant

Answer 16

The substance that is oxidized and thereby causes the reduction of some other substance in an oxidation-reduction reaction. (Section 20.1)

Question 17

reversible process

Answer 17

A process that can go back and forth between states along exactly the same path; a system at equilibrium is reversible if equilibrium can be shifted by an infinitesimal modification of a variable such as temperature. (Section 19.1)

Question 18

rotational motion

Answer 18

Movement of a molecule as though it is spinning like a top. (Section 19.3)

Question 19

second law of thermodynamics

Answer 19

A statement of our experience that there is a direction to the way events occur in nature. When a process occurs spontaneously in one direction, it is nonspontaneous in the reverse direction. It is possible to state the second law in many different forms, but they all relate back to the same idea about spontaneity. One of the most common statements found in chemical contexts is that in any spontaneous process the entropy of the universe increases. (Section 19.2)

Question 20

spontaneous process

Answer 20

A process that is capable of proceeding in a given direction, as written or described, without needing to be driven by an outside source of energy. A process may be spontaneous even though it is very slow. (Section 19.1)

Question 21

standard emf, also called the standard cell potential (E°)

Answer 21

The emf of a cell when all reagents are at standard conditions. (Section 20.4)

Question 22

standard hydrogen electrode (SHE)

Answer 22

An electrode based on the half-reaction 2 H+ (1 M).+ 2 e– → H2(1 atm). The standard electrode potential of the standard hydrogen electrode is defined as 0 V. (Section 20.4)

Question 23

standard molar entropy (S°)

Answer 23

The entropy value for a mole of a substance in its standard state. (Section 19.4)

Question 24

third law of thermodynamics

Answer 24

A law stating that the entropy of a pure, crystalline solid at absolute zero temperature is zero: S(0 K)

Question 25

translational motion

Answer 25

Movement in which an entire molecule moves in a definite direction. (Section 19.3)

Question 26

vibrational motion

Answer 26

Movement of the atoms within a molecule in which they move periodically toward and away from one another. (Section 19.3)

Question 27

voltaic (galvanic) cell

Answer 27

A device in which a spontaneous oxidation-reduction reaction occurs with the passage of electrons through an external circuit. (Section 20.3)

Question 28

watt

Answer 28

A unit of power; 1 w