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AP Chemistry > Chapter 13: Chemical Kinetics > Flashcards

Chapter 13: Chemical Kinetics Flashcards

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1
Q

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

A

rates of chemical reactions; reaction mechanisms

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2
Q

rate=

A

Δc/Δt

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3
Q

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

A

negative

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4
Q

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

A

positive number

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5
Q

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

A

concentration; time interval

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6
Q

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

A

instantaneous rate

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7
Q

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

A

average rate

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8
Q

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

A

slope of the tangent

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9
Q

the rate of reaction does not depend on

A

which species is measured

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10
Q

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

A

stoichiometric coefficient

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11
Q

the rate of a reaction is strongly influenced by the

A

concentrations of the reacting species

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12
Q

for the equation: aA + bB→products:

rate=

A

k[A]^x[B]^y

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13
Q

overall order:

A

sum of the individual orders

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14
Q

k is the

A

rate constant

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15
Q

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

A

ratios of reactants; concentration; initial rate

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16
Q

the rate law cannot be predicted from the

A

reaction stoichiometry

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17
Q

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

A

time

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18
Q

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

A

independent

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19
Q

(zero-order rate laws) reaction rate=

A

k

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20
Q

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

A

mol/L*s

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21
Q

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

A

zero-order kinetics

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22
Q

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

A

proportional

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23
Q

(first-order rate laws) reaction rate=

A

-Δ[A]/ Δ t → k[A]

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24
Q

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

A

s^-1

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25
Q

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

A

natural log (ln)

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26
Q

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

A

differential form

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27
Q

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

A

[A] =[A]0e-kt

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28
Q

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

A 
A0= concentration of A at time=0
k= rate constant
t= time
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29
Q

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

A

exponential decay;

ln[A]= ln[A]0 - kt

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30
Q

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

y-intercept=

A

-k; [A]0

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31
Q

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

A

fast reaction

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32
Q

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

A

1//2 its original value

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33
Q

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

A

rapid

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34
Q

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

A

0.693/k; independent

35
Q

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

A

raised to the second power

36
Q

(second-order rate laws) reaction rate=

A

-Δ[A]/ Δ t = k[A]2

37
Q

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

A

L/mol*s

38
Q

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

A

1/reactant concentration

39
Q

(second-order rate laws) integrated form:

A

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

40
Q

(second-order rate laws) t1/2=

A

1/k[A]

41
Q

(second-order rate laws) slope=

A

k

42
Q

collisions between molecules are necessary foe

A

reactions to occur

43
Q

the rates of most reactions increase dramatically with

A

temperature

44
Q

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

A

collide

45
Q

collision frequency: the number of … per second

A

moleclar collisions

46
Q

collision frequency: Z=

A

Z0[A][B]

47
Q

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

A

speeds; sizes

48
Q

experimental evidence shows that not every collision results

A

in a chemical reaction

49
Q

activation energy: the minimum collision energy required ….

A

for a reaction to occur

50
Q

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

A

rearrange bonds

51
Q

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

A

bounce off each other

52
Q

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

A

higher in energy

53
Q

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

A

unstable; transition state

54
Q

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

A

activated complex

55
Q

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

A

temperature

56
Q

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

A

fr= -e^Ea/RT

57
Q

as t increases, fr … and approaches …

A

increases; 100%

58
Q

predicted rate=

A

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

59
Q

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

A

orientation

60
Q

Rate= pZ0[A][B]e^-Ea/RT, where p is the…., Zo[A][B] is the …, and e^-Ea/RT is the …

A

steric factor; collision frequency; fraction exceeding Ea

61
Q

k=

A

Ae^-Ea/RT

62
Q

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

A

speed up; getting consumed

63
Q

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

A

activation energy; reaction rate; steric factor

64
Q

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

A

phase

65
Q

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

A

different phase

66
Q

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

A

proteins; bioligical reactions

67
Q

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

A

solid metal catalyst

68
Q

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

A

adsorption; activation

69
Q

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

A

surface

70
Q

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

A

reaction

71
Q

(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

A

correct geometry; 10^14; ase

72
Q

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

A

side reactions; yields

73
Q

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

A

elementary steps

74
Q

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

A

intermediates

75
Q

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

A

most likely to occur

76
Q

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

A

elementary steps

77
Q

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 …

A

overall balanced equation; experimentally determined rate law

78
Q

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

A

single; first order

79
Q

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

A

two; second order

80
Q

termolecular reaction: involves … molecules and a … rate law

A

three; third order

81
Q

rate-limiting: … step in proposed reaction mechanism

A

slow

82
Q

the rate-limiting step is the

A

rate-determing step

83
Q

the experimental rate law must agree with the

A

rate-determining step

AP Chemistry (24 decks)

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