Chapter 13: Chemical Kinetics Flashcards Preview

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Flashcards in Chapter 13: Chemical Kinetics Deck (83):
1

chemical kinetics: study of ... of chemical reactions and their ...

rates of chemical reactions; reaction mechanisms

2

rate=

Δc/Δt

3

the reactant concentration decreases during the reaction, so Δ[reactant] is

negative

4

by convention, the rate of reaction is always expressed as a

positive number

5

the average rate of reaction is equal to the change in ... divided by the ...

concentration; time interval

6

as the interval between measurements becomes smaller, the average rate approaches the

instantaneous rate

7

when a rate is measured over a time interval, it is called an

average rate

8

instantaneous rate: the ... to the curve at a particular time pt

slope of the tangent

9

the rate of reaction does not depend on

which species is measured

10

the rate of reaction is the absolute value of the rate of change of the concentration a substance divided by its ....

stoichiometric coefficient

11

the rate of a reaction is strongly influenced by the

concentrations of the reacting species

12

for the equation: aA + bB→products:
rate=

k[A]^x[B]^y

13

overall order:

sum of the individual orders

14

k is the

rate constant

15

initial rate method: repeat an experiment several times with different known ... and evaluate how th reaction rate changes with ..., important to measure the .. of the reaction

ratios of reactants; concentration; initial rate

16

the rate law cannot be predicted from the

reaction stoichiometry

17

rate laws can also be determined by expaning how the concentration of a reactant changes with ... during the course of a single experiment

time

18

(zero-order rate laws) some reactions show rates that are .... of the concentration of reactants

independent

19

(zero-order rate laws) reaction rate=

k

20

(zero-order rate laws) the units of a zero-order rate constant are:

mol/L*s

21

(zero-order rate laws) if the graph of reactant concentration vs. time is a straight line, the reaction obeys

zero-order kinetics

22

(first-order rate laws) some reactions show rates that are .... to the concentration of the reactant

proportional

23

(first-order rate laws) reaction rate=

-Δ[A]/ Δ t → k[A]

24

(first-order rate laws) first-order rate constant:

s^-1

25

(first-order rate laws) if the graph of the ... of reactant concentrations vs. time is a straight line, the reaction obeys first-order kinetics

natural log (ln)

26

(first-order rate laws) reaction rate= k[A] is referred to as the ... of the rate law

differential form

27

(first-order rate laws) the rate law can be written in the following integrated form:

[A] =[A]0e-kt

28

(first-order rate laws) for [A] =[A]0e-kt,

A0= concentration of A at time=0
k= rate constant
t= time

29

(first-order rate laws) the integrated rate equation describes ..., another form includes:

exponential decay;
ln[A]= ln[A]0 - kt

30

(first-order rate laws) slope of the line=
y-intercept=

-k; [A]0

31

(first-order rate laws) a large value for k implies a

fast reaction

32

(first-order rate laws) half-life: the time needed for the concentration of a reactant to decrease to

1//2 its original value

33

(first-order rate laws) a short half-life indicates a ... reaction

rapid

34

(first-order rate laws) for first-order, t1/2= .... and is .... of the concentration of the reactant

0.693/k; independent

35

(second-order rate laws) some reactions show rates that are proportional to the concentration of the reactant...

raised to the second power

36

(second-order rate laws) reaction rate=

-Δ[A]/ Δ t = k[A]2

37

(second-order rate laws) the units of a second order rate constant are

L/mol*s

38

(second-order rate laws) if the graph of .... vs. time is a straight line, the reaction obeys second-order kinetics

1/reactant concentration

39

(second-order rate laws) integrated form:

1/[A]= 1/[A]0 + kt

40

(second-order rate laws) t1/2=

1/k[A]

41

(second-order rate laws) slope=

k

42

collisions between molecules are necessary foe

reactions to occur

43

the rates of most reactions increase dramatically with

temperature

44

collision theory: basic assumption= molecules must ... in order to react

collide

45

collision frequency: the number of ... per second

moleclar collisions

46

collision frequency: Z=

Z0[A][B]

47

Z0 is a proportionality constant that depends on the ... and ... of A and B

speeds; sizes

48

experimental evidence shows that not every collision results

in a chemical reaction

49

activation energy: the minimum collision energy required ....

for a reaction to occur

50

activation energy: only collisions with enough energy to .... can result in the formation of products

rearrange bonds

51

activation energy: if the total energy of colliding species is too small, the molecules simply

bounce off each other

52

(activated complex→[X]*) intermediate species in chemical reactions are ... than either the reactants or products of a chemical reaction

higher in energy

53

(activated complex→[X]*) the high-energy activated complex is very ... and is also referrred to as the ...

unstable; transition state

54

(activated complex→[X]*) the activation energy is the energy needed to form the ... from the reactants

activated complex

55

the number of collisions with energies that exceed Ea grows exponentially with

temperature

56

the fraction of collisions with energy in excess of Ea can be derived from

fr= -e^Ea/RT

57

as t increases, fr ... and approaches ...

increases; 100%

58

predicted rate=

Z0[A][B]e^-Ea/RT

59

steric factor: not all collissions with energies that exceed Ea are productive;
the geometry of collisions must also be considered- not every collision occurs with the reactants in the correct .... to produce products

orientation

60

Rate= p*Z0[A][B]*e^-Ea/RT, where p is the...., Zo[A][B] is the ..., and e^-Ea/RT is the ...

steric factor; collision frequency; fraction exceeding Ea

61

k=

Ae^-Ea/RT

62

catalysts are substances that ... the rate of reaction without ... in the reaction

speed up; getting consumed

63

catalysts generally lower ... and increase ... at any given temperature. Some may increase the ...

activation energy; reaction rate; steric factor

64

homogenous catalysts: present in the same .... as the reacting molecules

phase

65

heterogenous catalysts: present in a .... than the reacting molecules

different phase

66

enzymes: large molecules (usually ...) that catalyze specific ...

proteins; bioligical reactions

67

numerous gaseous reactions are catalyzed via absorption to the surface of a

solid metal catalyst

68

(heterogenous catalysis) step 1: ... and ... of the reactants

adsorption; activation

69

(heterogenous catalysis) step 2: migration of the adsorbed reactants to the

surface

70

(heterogenous catalysis) step 3: ... of the adsorbed substances

reaction

71

(enzymes) enzymes interact with reactant molecules in a way that places them in the ... to form the products;
can increase reaction rates up to ..
often end with an ... suffix

correct geometry; 10^14; ase

72

reactions can be manipulated to decrease ... and improve ... if we know the appropriate reaction mechanism

side reactions; yields

73

a reaction mechanism is the sequence of ... that lead from reactants to products

elementary steps

74

many reactions require multipe steps with .... that are produced, then consumed, during the course of the reaction

intermediates

75

sometimes more than one reaction mechanism is possible and further experimentation can help determine which mechanism is

most likely to occur

76

catalysts may allow for a different set of ... to proceed as compared to those observed for an uncatalyzed reaction

elementary steps

77

for a reactio mechanism to be valid: the sum of the elementary steps must give the ... for the reaction
the mechanism must agree with the ...

overall balanced equation; experimentally determined rate law

78

unimolecualr reaction: involves a ... molecule and a ... rate law

single; first order

79

bimolecular reaction: involves ... molecules and a .... rate law

two; second order

80

termolecular reaction: involves ... molecules and a ... rate law

three; third order

81

rate-limiting: ... step in proposed reaction mechanism

slow

82

the rate-limiting step is the

rate-determing step

83

the experimental rate law must agree with the

rate-determining step