chapter 4

Question 1

thermodynamics

Answer 1

deals with energy changes accompanying chemical and physical transformations
- describes properties of systems at equilibrium

Question 2

kinetics

Answer 2

variation of reaction rates with different condition and concentrations of reagents
- rates: how fast something happens

Question 3

3 steps of chain reaction mechanism

Answer 3

1. initiation
2. propagation
3. termination

Question 4

initiation

Answer 4

generates reactive intermediate

Question 5

propagation

Answer 5

reactive intermediate reacts with stable molecule to form product and another reactive intermediate

Question 6

termination

Answer 6

reactive intermediates destroyed

Question 7

what kind of light is used to split Cl2

Answer 7

blue light (hv)

Question 8

reactive intermediate

Answer 8

short-lived series never present in high concentration because it reacts as quickly as it is formed

Question 9

free radicals

Answer 9

species with unpaired electrons

Question 10

stability of free radicals

Answer 10

methyl < primary < secondary < tertiary < allylic/benzylic

Question 11

stability of free radicals according to hybridization

Answer 11

sp < sp2 < sp3

Question 12

if Keq is larger than 1…

Answer 12

then reaction is favored from left to right

Question 13

if Keq is less than 1

Answer 13

reaction is favored from right to left

Question 14

Gibbs free energy (delta G)

Answer 14

change in free energy:
(free energy of products) - (free energy of reactants)

Question 15

delta H (enthalpy)

Answer 15

(enthalpy of products) - (enthalpy of reactants)

Question 16

delta G in relation to H,T,S

Answer 16

delta G = delta H - T(delta S)

Question 17

delta S (entropy)

Answer 17

(entropy of products) - (entropy of reactants)

Question 18

reactions tend to favor products with the ________ enthalpy

Answer 18

lowest

Question 19

change in enthalpy (heat of reaction)

Answer 19

amount of heat evolved or consumed in the course of a reaction

Question 20

do exergonic reactions have a negative or positive g

Answer 20

negative

Question 21

do endergonic reactions have a negative or positive g

Answer 21

positive

Question 22

if weaker bonds are broken and stronger bonds are formed, it is an ____________ reaction

Answer 22

exothermic

Question 23

if stronger bonds are broken and weaker bonds are formed, it is an ____________ reaction

Answer 23

endothermic

Question 24

entropy

Answer 24

measure of randomness, disorder, or freedom of motion

Question 25

reactions favor products with the _________ entropy

Answer 25

greatest

Question 26

bond-dissociation enthalpy (BDE)

Answer 26

amount of enthalpy required to break a particular bond homolytically

Question 27

homolytic cleavage

Answer 27

each bonded atom retains one of bond's two electrons - free radicals result

Question 28

heterolytic cleavage

Answer 28

one of the atoms retains both electrons - ions results

Question 29

is energy consumed or released when bonds are formed

Answer 29

released

Question 30

is energy consumed or released when bonds are broken

Answer 30

consumed

Question 31

are bond-dissociation enthalpies positive or negative

Answer 31

positive (endothermic)

Question 32

what is the rate of reaction a measure of

Answer 32

how fast the products appear and the reactants disappear

Question 33

reaction rates depend on the concentration of the __________

Answer 33

reactants

Question 34

the values of the powers in a rate equation are determined _____________

Answer 34

experimentally

Question 35

activation energy

Answer 35

energy difference between the reactants and the transition state

Question 36

transition state

Answer 36

highest-energy state in a molecular collision that leads to reaction

Question 37

is a transition state stable or unstable

Answer 37

unstable

Question 38

is a transition state an intermediate

Answer 38

no

Question 39

is the Ea value always positive or negative

Answer 39

positive

Question 40

catalysts

Answer 40

lower the activation energy and increase the reaction rate, but don't affect energies of reactants/products

Question 41

enzymes

Answer 41

biological catalysts

Question 42

which step determines the rate of a reaction

Answer 42

the highest-energy step (transition state)

Question 43

does temperature usually increase or decrease reaction rate

Answer 43

increase - within limits

Question 44

is the transition state of an endothermic reaction closer to the reactants or products

Answer 44

produc ts

Question 45

is the transition state of an exothermic reaction closer to the reactants or products

Answer 45

reactants

Question 46

is chlorination more or less selective

Answer 46

less

Question 47

is bromination more or less selective

Answer 47

more

Question 48

is chlorination exothermic or endothermic

Answer 48

exothermic

Question 49

is bromination exothermic or endothermic

Answer 49

endothermic

Question 50

rate-limiting step of bromination and chlorination

Answer 50

first propagation step

Question 51

Hammond's postulate

Answer 51

related species that are closer in energy are closer in structure

Question 52

is there a large or small difference in Ea of bromination

Answer 52

large

Question 53

is there a large or small difference of Ea in chlorination

Answer 53

small

Question 54

radical inhibitors

Answer 54

slow down or prevent free-radical reactions

Question 55

carbocation

Answer 55

species that contains a C atom bearing a positive charge

Question 56

2 ways an alkyl group stabilizes a carbocation

Answer 56

1. inductive effect 2. partial overlap of filled orbitals with empty ones

Question 57

4 types of reactive intermediates

Answer 57

1. carbocation 2. radical 3. carbanion 4. carbene

Question 58

stability of carbocations

Answer 58

resonance > 3 > 2 > 1 > methyl

Question 59

hybridization of carbocations

Answer 59

sp2

Question 60

hybridization of free radicals

Answer 60

sp2

Question 61

stability of radicals

Answer 61

resonance > 3 > 2 > 1 > methyl

Question 62

carbanion

Answer 62

has trivalent carbon atom that bears a negative charge - Lewis base)

Question 63

hybridization of carbanion

Answer 63

sp3

Question 64

stability of carbanions

Answer 64

resonance > methyl > 1 > 2 > 3

Question 65

carbenes

Answer 65

uncharged reactive intermediates containing a divalent carbon atom

Question 66

hybridization of carbene

Answer 66

sp2

Question 67

what happens when 2 carbenes collide

Answer 67

make alkene (double bond)

Question 68

properties of carbocations

Answer 68

electrophilic, strong acids

Question 69

properties of radicals

Answer 69

electron-deficient

Question 70

properties of carbanions

Answer 70

nucleophilic, strong bases

Question 71

properties of carbenes

Answer 71

both nucleophilic and electrophilic