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Chemistry AP > chapter 12: chemical kinetics > Flashcards

chapter 12: chemical kinetics Flashcards

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1
Q

what are reaction rates?

A

the change in concentration of a reaction or product per unit time

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2
Q

what is the formula for rate?

A

delta[A]/ delta t

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3
Q

what is instantaneous rate?

A

value of the rate at a particular time.

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4
Q

how can instantaneous rate be obtained?

A

it can be obtained by computing the slope of a line tangent to the curve at that point

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5
Q

what does a rate law show?

A

shows how the rate depends on the concentrations of reactants

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6
Q

what is rate measured in?

A

mol/ L s

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7
Q

how do you express rate? (rate law form)

A

rate = k[A]^n [B]^m

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8
Q

what does k represent?

A

rate constant

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9
Q

what does n represent?

A

the order of the reactant

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10
Q

do the concentrations of the products appear in the rate law? explain.

A

the concentrations of the products do not appear in the rate law because the reaction rate is being studied under conditions where the reverse reaction does not contribute to the overall rate.

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11
Q

how can the value of n be determined?

A

the value of the exponent n must be determined by experiment; it can’t be written from the balanced equation

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12
Q

what are the types of rate laws?

A

differential and integrated

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13
Q

what is a differential rate law?

A

shows how the rate of a reaction depends on concentrations

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14
Q

what is an integrated rate law?

A

shows how the concentrations of species in the reaction depend on time

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15
Q

why is knowing the rate law for a reaction important?

A

it is important mainly because we can usually infer the individual steps involved in the reaction from the specific form of the rate law

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16
Q

how do you find the overall reaction order?

A

n+m (exponents)

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17
Q

what is the rate law for a first order reaction?

A

k[A]

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18
Q

what is the integrated rate law for a first order reaction?

A

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

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19
Q

what does [A]0 stand for?

A

A knot - initial concentration of A

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20
Q

what is the half life formula for a first order reaction?

A

t1/2 = 0.693/ k

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21
Q

how does the half life of a first order reaction look?

A

stays constant

22
Q

how do you get a straight line on a first order reaction graph?

A

plot ln[A] vs. t

23
Q

what is the rate law of a second order reaction?

A

rate = k[A]^2

24
Q

what is the integrated rate law of a second order reaction?

A

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

25
Q

what is the half life of a second order reaction?

A

t1/2 = 1/ k[A]0

26
Q

how does the half life of a second order reaction look like?

A

it doubles each time

27
Q

how do you get a straight line on a second order reaction?

A

plot 1/ [A] vs. t

28
Q

what is the rate law of a zero order reaction?

A

rate = k[A]^0 = k

29
Q

what is the integrated rate law of a zero order reaction?

A

-kt + [A]0

30
Q

what is the half life of a zero order reaction?

A

t1/2 = [A]0 / 2k

31
Q

what does the half life of a zero order reaction look like?

A

it is half of the previous life

32
Q

how do you get a straight line on a zero order reaction?

A

plot [A] vs. time

33
Q

what is an intermediate?

A

an intermediate is formed in one step and used up in a subsequent step and this is never seen as a product in the overall balanced reaction

34
Q

what is a unimolecular reaction?

A

reaction involving one molecule ; first order

35
Q

what is a bimolecular reaction?

A

reaction involving the collision of 2 species; second order

36
Q

what is a termolecular reaction?

A

reaction involving the collision of 3 species; third order

37
Q

what is the rate determining step?

A

the slowest step in a series of elementary steps

38
Q

using elementary steps, how can you determine the rate law?

A

use the reactants of the slowest step and add exponents as necessary

39
Q

what is a catalyst (elementary steps)?

A

a substance which is consumed in one step and produced in a later step

40
Q

what must happen to molecules for them to react?

A

molecules must collide to react

41
Q

what are the main factors in the collision model?

A

1) activation energy
2) temperature
3) molecular orientations

42
Q

what is activation energy?

A

energy that must be overcome to produce a chemical reaction

43
Q

what must the collision of molecules involve?

A

a collision must involve enough to produce the reaction (must equal or exceed the Ea)

44
Q

what does the relative orientation of reactions allow?

A

relative orientation of the reactants must allow formation of any new bonds necessary to produce products

45
Q

what is the linear form of the arrhenius equation?

A

ln (k) = -Ea/R (1/T) + ln(A)

46
Q

what is the gas constant?

A

8.3145

47
Q

what is a catalyst?

A

a substance that speeds up reaction without being consumed itself. it provides a new pathway for the reaction with a lower Ea.

48
Q

what is adsorption?

A

collection of one substance on the surface of a solid catalyst

49
Q

what is desorption?

A

the movement of products (or reactants) from the surface of the catalyst

50
Q

what reaction order are heterogeneously-catalyzed usually?

A

zero order.

51
Q

what happens once a heterogenous catalyst is covered by reactants if concentration is increased?

A

once the catalyst is covered by reactants, any further increase in reactant concentration has no effect on the rate, as no active sites are accessible for the reaction species.

52
Q

what are homogenous catalysts?

A

exists in the same phase as the reacting molecules. enzymes are nature’s catalyst.

Chemistry AP (4 decks)

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