Ch 18 Introduction to Electrochemistry

Question 1

electrons are transferred from one reactant to
another.

Answer 1

oxidation/reduction reaction e

Question 2

A substance that has a strong affinity for electrons

Answer 2

oxidizing agent,

Question 3

Species that donates electrons to another species.

Answer 3

Reducing agent

Question 4

the reaction is carried out in an ____________ in which the reactants do not come in direct contact with one another.

Answer 4

electrochemical cell

Question 5

are widely used in electrochemistry to prevent
mixing of the contents of the two electrolyte solutions making up electrochemical cells.

Answer 5

Salt bridges

Question 6

A unique aspect of oxidation/reduction reactions is that the transfer of
electrons, and thus an identical net reaction, can often be brought about in an ____________ in which the oxidizing agent and the reducing agent are physically separated from one another

Answer 6

electrochemical cell

Question 7

It isolates the reactants but maintains electrical contact between the
two halves of the cell

Answer 7

salt bridge

Question 8

When a voltmeter of high internal resistance is connected as
shown or the electrodes are not connected externally, the cell is said to be at _________ and delivers the full cell potential

Answer 8

open circuit

Question 9

A circuit where no net reaction
occurs in the cell, although we shall show that the cell has the potential for doing
work.

Answer 9

open circuit

Question 10

The voltmeter measures the potential difference, or _________, between the two
electrodes at any instant.

Answer 10

voltage

Question 11

is a measure of the tendency of the cell reaction to proceed toward equilibrium.

Answer 11

voltage

Question 12

In a salt bridge, the two ends of the bridge are
fitted with ____________ to prevent liquid from siphoning from one part of the cell to
the other.

Answer 12

sintered glass disks/ porous materials

Question 13

The equilibrium-constant
expression

Answer 13

Keq = oxidized/ reduced

Question 14

As the reaction goes on in an electrochemical cell, the cell potential, when the circuit is open, _________ and approaches ____________
as the overall reaction approaches equilibrium.

Answer 14

decreases continuously , zero

Question 15

The electrodes in some cells share a
common electrolyte; these are known
as

Answer 15

cells without liquid junction

Question 16

An electrochemical cell consists of two conductors

Answer 16

electrodes

Question 17

is an electrode where
reduction occurs.

Answer 17

cathode

Question 18

is an electrode where oxidation occurs.

Answer 18

anode

Question 19

Types of Electrochemical Cells

Answer 19

galvanic or electrolytic cells

Question 20

The cell that store electrical energy

Answer 20

Galvanic cells

Question 21

The cell that consume electricity

Answer 21

electrolytic cells

Question 22

are usually made from galvanic cells connected in series to produce higher voltages than a single cell can produce

Answer 22

Batteries

Question 23

Galvanic cells operate spontaneously, and the net reaction during discharge is called the

Answer 23

spontaneous cell reaction.

Question 24

in contrast to a voltaic cell, requires an external source of
electrical energy for operation.

Answer 24

electrolytic cell

Question 25

reversing the current reverses the cell reaction.

Answer 25

reversible cell

Question 26

reversing the current causes a different half-reaction to occur at one or both of the electrodes.

Answer 26

irreversible cell

Question 27

was one of the earliest galvanic cells to find widespread practical application. It was used in the mid-1800s to power telegraphic communication systems.

Answer 27

Daniell Gravity Cell

Question 28

In the shorthand notation to describe electrochemical cells, a single vertical line indicates a _________ at which a potential develops

Answer 28

phase boundary

Question 29

In the shorthand notation to describe electrochemical cells, the double vertical lines represent _____, one at each end of the salt bridge

Answer 29

two-phase boundaries

Question 30

The junction potential results from differences in the rates at which the ions in the cell compartments and the salt bridge migrate across the interfaces.

Answer 30

liquid-junction potential

Question 31

A liquid-junction potential can amount to as much as several hundredths of a volt but can be negligibly small if the electrolyte in the salt bridge has an anion and a cation that migrate at nearly the same rate. A saturated solution of _____________is the electrolyte that is most widely used.

Answer 31

potassium chloride, KCl

Question 32

___________ carry the charge within the electrodes as well as the external conductor. Notice that by convention, __________, which is normally indicated by the symbol I, is opposite in direction to electron flow

Answer 32

Electrons, current

Question 33

are the charge carriers within the cell

Answer 33

Anions and cations

Question 34

The phase boundary between an electrode and its solution is called an .

Answer 34

interface

Question 35

Equation than relates the cell potential, Ecell, to the free energy of the reaction, to the equilibrium constant

Answer 35

△G = -nFEcell = -RT ln Keq

Question 36

The ____ of a substance is a reference state that allows us to obtain relative values of such thermodynamic quantities as free energy, activity, enthalpy, and entropy

Answer 36

standard state

Question 37

If the reactants and products are in their standard states, the resulting cell potential is called the

Answer 37

standard cell potential

Question 38

This rule implies that we always measure the cell potential by connecting the positive lead of the voltmeter to the right-hand electrode in the schematic or cell drawing

Answer 38

plus right rule.

Question 39

The leads of voltmeters are color coded. The__________ is red, and the _________ is black.

Answer 39

positive lead, common lead

Question 40

The reaction is not spontaneous cell reaction when Ecell is _________, and △G is thus _______.

Answer 40

negative, positive

Question 41

This generally agreed-upon reference half-cell against which all others are compared. Such an electrode must be easy to construct, reversible, and highly reproducible in its behavior. The universal reference electrode

Answer 41

standard hydrogen electrode (SHE)

Question 42

The standard hydrogen electrode is sometimes called the

Answer 42

normal hydrogen electrode (NHE).

Question 43

The metal conductor is a piece of platinum that has been coated, or ______________, with finely divided platinum (platinum black) to increase its specific surface area.

Answer 43

platinized

Question 44

______ is a layer of finely divided platinum that is formed on the surface of a smooth platinum electrode by electrolytic deposition of the metal from a solution of chloroplatinic acid, H2PtCl6. It provides a large specific surface area of platinum

Answer 44

Platinum black

Question 45

The assigned value for the potential of standard hydrogen electrode (SHE) at all temperatures

Answer 45

0.000 V

Question 46

is defined as the potential of a cell in which the electrode in question is the right-hand electrode and the standard hydrogen electrode is the left-hand electrode

Answer 46

electrode potential

Question 47

of a half-reaction is defined as its electrode potential when the activities of the reactants and products are all unity

Answer 47

standard electrode potential, E^0

Question 48

A metal ion/metal half-cell is sometimes called a .

Answer 48

couple

Question 49

An ___________is by definition a reduction potential or the half-reactions written as reductions

Answer 49

relative electrode potential

Question 50

An_______________is a measure of the extent to which the concentrations of the species in a half-cell differ from their equilibrium values

Answer 50

electrode potential

Question 51

The _______________for a half-reaction, E^0, is defined as the electrode potential when all reactants and products of a half-reaction are at unit activity.

Answer 51

standard electrode potential

Question 52

A ______________is the electrode potential when the ratio of analytical concentrations of reactants and products of a half-reaction are exactly 1.00 and the molar concentrations of any other solutes are specified. To distinguish the formal potential from the standard electrode potential a prime symbol is added to E^0' .

Answer 52

formal potential

Question 53

are empirical potentials that compensate for the types of activity and competing equilibria effects that we have just described.

Answer 53

formal potential