Chapter 4

Question 1

According to the Arrhenius definition, an acid is a substance that dissolves in water to produce … A base is a substance that dissolves in water to produce …

Answer 1

H+ ions; OH- ions

Question 2

An H+ ion immediately combines with a water molecule to give a …

Answer 2

hydronium ion

Question 3

According to Bronsted-Lowry def, an acid is a …, a base is a …, and an acid-base reaction is a … reaction

Answer 3

proton donor; proton acceptor; proton-transfer reaction

Question 4

any pair of molecules or ions that can be interconverted by transfer of a proton is called a

Answer 4

conjugate acid-base pair

Question 5

when an acid transfers a proton to a base, the acid is converted to its …

Answer 5

conjugate base

Question 6

when a base accepts a proton, it is converted to its

Answer 6

conjugate acid

Question 7

the members of a conjugate acid-base pair differ by a

Answer 7

proton

Question 8

for acid-base reactions, we write the Lewis structures of reactants and products, showing all valence electrons. we then use … to show the change in position of electron pairs during the reaction. the tail of the curved arrow is located at an …, either a lone pair or a bonding pair. The head of the curved arrow shows the new … of the electron pair

Answer 8

curved arrows; electron pair; location

Question 9

a curved arrow originating at a lone pair and pointing to an adjacent atom indicates …, while an arrow originating at a bonding electron pair and pointing toward a previously bonded atom indicates a …

Answer 9

formation of a new bond; breaking of that bond

Question 10

the more stable charged species is the one in which the charge is more …

Answer 10

delocalized

Question 11

relative charge delocalization can often be understood by considering

Answer 11

resonance

Question 12

we see that protonation of a carboxyl group occurs preferentially on the … oxygen because this cation has a greater … of charge

Answer 12

carbonyl; delocalization

Question 13

proton transfer reactions also occur with compounds having … electrons

Answer 13

pi

Question 14

the result of proton transfer reactions with pi bonds is the formation of a …., a species in which one of its carbons has only … electrons in its valence shell and carries a charge of …

Answer 14

carbocation; six; +1

Question 15

any quantitative measure of the acidity of organic acids or bases involves measuring the … of the various components in an acid-base equilibrium. the strength of an acid is then expressed by an …

Answer 15

equilibrium concentrations; equilibrium constant

Question 16

dissocation of the acid, …, in water gives an anion …, and the hydronium ion.

Answer 16

HA; A-

Question 17

The general chemical equation and equilibrium constant for ionization of an acid is:
… + … (equilibrium arrows) … + …
Keq =

Answer 17

HA + H2O; A- + H3O+; [H3O+][A-]/[HA][[H2O]

Question 18

because water is the solvent for this reaction and its concentration changes very little when HA is added to it, we can treat the concentration of water as a constant equal to …

Answer 18

1000 g/L

Question 19

acid dissociation constant, Ka =

Answer 19

[H3O+][A-]/[HA]

Question 20

acid strengths are often expressed as …

Answer 20

pKa (-log10Ka)

Question 21

the larger the value of pKa, the … the acid

Answer 21

weaker

Question 22

the smaller the value of pKa, the … the acid

Answer 22

stronger

Question 23

the weaker the acid, the … its conjugate base

Answer 23

stronger

Question 24

the stronger the acid, the … its conjugate base

Answer 24

weaker

Question 25

if the pKa of an acid is near zero, then the equilibrium constant for the reaction of that acid protonating water is near

Answer 25

1

Question 26

negative pKa values correlate to acids with equilibrium constants ..., while positive pKa values are for acids with equilibrium constants ...

Answer 26

greater than 1; less than 1

Question 27

in an acid-base reaction, the position of equilibrium always favors reaction of the .... acid and ... base to form the ... acid and ... base

Answer 27

stronger; stronger; weaker; weaker

Question 28

a reaction mechanism describes which bonds are ... and which are ..., as well as the ... and ... of the various bond-breaking and bond-forming steps

Answer 28

broken; formed; order; relative rates

Question 29

most chemical reactions occur via

Answer 29

collisions

Question 30

the velocity at which the molecules move through the vessel is proportional to their ...

Answer 30

kinetic energy

Question 31

higher-energy collisions occur between molecules possessing larger ... During collision, the structures of the molecule ... and ..., and collisions of higher energy lead to larger ... in structure

Answer 31

kinetic energy; contort; flex; distortions

Question 32

at higher temperatures, the energy of the collisions is greater because the molecules are moving more ...

Answer 32

rapidly

Question 33

reactions that result by virtue of the kinetic energy put into a reaction vessel due to temperature are called

Answer 33

thermal reactions

Question 34

during collisions, the kinetic energy of the reactants is converted into ..., which is stored in the chemical structures in the form of the ..., and the energy is released as the molecules again adopt their ...

Answer 34

potential energy; structural strains; optimal geometries

Question 35

if molecules collide with enough force, bonds will ... some collisions cause distortions that lead to ... of bonds

Answer 35

break; rearrangements

Question 36

during a collision process that yields a reaction, a structure forms that is called the ..., also commonly called the ... It has a particular geometry possessing ... and ... bonds, and it is so ... that it transitions to .. that are less ..

Answer 36

transition state; activated complex; partially broken; partially formed; strained; new structures; strained

Question 37

chemists use reaction coordinate diagrams to show the ... for molecules involved in a chemical reaction

Answer 37

reaction coordinate diagrams

Question 38

the transition state exists at the ... point on a reaction coordinate diagram and they last less than one picosecond

Answer 38

highest energy

Question 39

bond breaking in the reactants and bond formation in the products occur ... upon collision

Answer 39

simultaneously

Question 40

every point along the reaction coordinate that is not a reactant or product represents a chemical structure that has characteristics of ...

Answer 40

both the reactants and the products

Question 41

thermodynamics is the study of the relative energies between any two entities on a reaction coordinate diagram that are shown in

Answer 41

wells

Question 42

gibbs free energy has a naught superscript which indicates standard states of ... K and ... atm

Answer 42

298; 1

Question 43

change in Gibbs free energy =

Answer 43

-RTlnKeq

Question 44

A negative change in G. free energy is ... while a positive value is

Answer 44

favorable; unfavorable

Question 45

when change in Gibbs is greater than 0, Keq is ... (...), and when it is equal to 0, Keq = ...; and when it is less than 0, Keq is ... (...)

Answer 45

less than 1; unfavorable; 1; greater than 1; favorable

Question 46

change in Gibss is a function of the change in two terms: ... and ... deltaGnaught = ...

Answer 46

entropy; enthalpy; change in enthalpy - T*change in entropy

Question 47

enthalpy is the energy contained in ... and ..

Answer 47

chemical bonds; solvation

Question 48

the difference in enthalpy between reactants and products is called the ...

Answer 48

heat of reaction

Question 49

if the bonds formed in the products are stronger than the bonds in the reactant, heat will be ..., the solution will warm, and the reaction is called ...

Answer 49

released; exothermic

Question 50

if the bonds formed in the products are weaker, heat will be absorbed from the solution so that it cools and ther eaction is

Answer 50

endothermic

Question 51

enthalpy reflects the intrinsic ... of the chemical structures involvedi n the reaction

Answer 51

stability

Question 52

structures that have stronger bonds and/or that are better solvated are more ... and thereby have lower ...

Answer 52

stable; enthalpy

Question 53

entropy measures ... versus ..., and ... is favorable

Answer 53

disorder; order; disorder

Question 54

all systems become more stable as the number of freely moving particles ... and the chaotic movement of the partic lces ...

Answer 54

increases; increases

Question 55

a favorable change in entropy is defined as a ... value and represents an increase in ..., whereas an increase in order is reflected by a ... value

Answer 55

positive; disorder; negative

Question 56

for an acid to transfer its proton to a base, the two entities must ... with a specific geometry. the trajectory of the base must be toward the ... of H-A

Answer 56

collide; H

Question 57

the lowest energy pathway for passing the proton from the acid to the base is a ... approach

Answer 57

linear

Question 58

(how to stabilize A-) - having the negative charge on a more ... atom - having the negative charge on a ... atom - ... the negative charge as described by ... - ... the negative charge onto electron-withdrawing groups by the ... - having the negative charge in an orbital with more ...

Answer 58

electronegative; larger; delocalizing; resonance contributing structures; spreading; inductive effect; s character

Question 59

the relative acidity within a period of the Periodic table is related to the ... of the atom in the anion that bears the negative charge. the greater it is, the more ... its electrons are held, and the more ... the anion is

Answer 59

electronegativity; strongly; stable

Question 60

the relative acidity of hydrogen acids within a group is related to the ... of the atom bearing the negative charge. the negative charge is ... in a larger atom, so its mroe stable

Answer 60

size; spread over a larger volume

Question 61

inductive effect: the ... of e- density of a covalent bond caused by the .. of a nearby atom

Answer 61

polarization; electronegativity

Question 62

electrons in an s orbital are ... in energy than those in a p orbital and are thus held more ... to the nucleus. thus, the more s character in a hybrid orbital, the more ... the atom and the more ... a hydrogen bonded to it

Answer 62

lower; tightly; electronegative; acidic

Question 63

of the three types of compounds, the carbon in an ... is the most electronegative (it has the most s character, of 50%)

Answer 63

alkyne

Question 64

lewis acid: accepts a pair of ... in forming the new ... and acquires a ... formal charge (these are ...)

Answer 64

electrons; covalent bond; negative; electrophiles

Question 65

lewis base: donates the pair of electrons and aquires a ... formal charge (these are ...)

Answer 65

positive; nucleophiles

Question 66

donating an electron pair means that it becomes ... to form a ...

Answer 66

shared; covalent bond

Question 67

if both reactants are equally but oppositely charged, a lewis acid-lewis base reaction result in the formation of a new covalent bond in which the product has no

Answer 67

charge

Question 68

All bronsted-lowry acids are ... acids, Lewis acids may be ... or ...

Answer 68

protic; protic; aprotic