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Flashcards in Kinetecs Deck (71):
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Rates of chemical change

Change in the concentration of a specific element over a period of time
Units of M per second
See the book for practice

1

Rate law

Rate=k[A]^n

2

Instantanteous Rate

Limit as (t-initial)+(t-final) approaches the designated time
In Δ[elementConcentration]/Δt

3

First order reactant

The rate varies directly with the concentration of reactant-A, forms a linear curve
Rate=k[A]^1

4

Second order reactant

The rate of the reaction changes exponentially with a change in the concentration of the A reactant
Rate=k[A]^2

5

Reaction order for multiples reactants

Rate=k*([A]^m)*([B]^n)

The order of the individual reactant remains unchanged in the reaction, only the k-value changes (depends on the how many, as well as which, reactants factor into the problem here

6

Integrated rate Law

The concentrations of the reactants is related to time time

7

First order integrate rate law

Natrual log [A] as a ratio to its original concentration for the simplest linear function

Ln([A]sub-t)/([A]sub-0)=-k*t

Write it out for practice

8

Second-order integrated rate law

Describes the reciprocal of the concentration of [A] in terms of 't'
Basically just the inverse of the zero-order law

1/([A]sub-t)=-k*t +(1/[A]sub-0)

9

Zero-order integrated rate law

Describes concentration as a linear function of (t)

[A]sub-t= -k*t +[A]sub-0

10

Half life of a reaction

T sub-1/2= 0.693/k

Or

T sub-1/2= ([A]sub-0)/2k

11

Arrhenius Equation

k= Ae^ ((-Ea)/RT)

A=frequency factor, individual to each reaction
Ea=activation energy
R= gas constant
T= temperature in kelvin

12

Activation energy

Energy that much be accumulated for the reaction to take plac

13

Activated complex (transition state)

The high energy state all molecules go through to go from reactants to products

14

Frequency factor (A)

Number of time the reactants approach the activation energy level per minute

15

Exponential factor

e^(-Ea/RT)
Represents a number 0 through 1 represents the fraction of molecules that have enough energy to participate in the reaction

16

Arrhenius plot

Linear equation that represents the relationship between the temperature and the 'k-value'

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

17

Arrhenius Equation (two point form)

Ln (k2/k1)=Ea/R*(1/T1-1/T2)

18

Collision Model

The reaction in question calls for an energetic collision between two molecules

19

Orientation factor (p)

Numerical representation of the angle at which the molecules must collide with one another for the reaction to occur

20

Collision frequency (z)

Number of particle collisions that occur per unit of time

21

K-value from Collision model

k=p*z*(exponentialFactor)

Write it out

22

Reaction mechanism

Series of individual chemical equations by which an overall chemical reaction occurs

23

Elementary step

The simplest possible step, chemical equation) into which an entire reaction mechanism can always be broken down

24

Law of elementary steps in reaction mechanisms

An entire reaction mechanism can always be broken down into one simple chemical equation that describes the entire process, known as the elementary step

25

Reaction intermediate

A molecule formed in an elementary step of a reaction mechanism but broken down by another reaction mechanism's elementary step

26

Molecularity

Number of reactant particles involved in a step

27

Unimolecular reaction

Only one reactant is required

28

Bimolecular

Two reactants are required

29

Termolecular

Elementary steps in which three reactant particles collide,
Very rare to occur

30

Rate-determining step

The slowest step in the reaction mechanism

31

Activation energy in reaction mechanisms

Each require a little more energy, constant energy must be supplied

32

Instantanteous Rate

Limit as (t-initial)+(t-final) approaches the designated time
In Δ[elementConcentration]/Δt

33

Reaction order for multiples reactants

Rate=k*[A]^m*[B]^n

34

First order integrate rate law

Ln([A]sub-t)/([A]sub-0)=-k*t

Write it out for practice

35

Second-order integrated rate law

1/([A]sub-t)=-k*t +(1/[A]sub-0)

36

Zero-order integrated rate law

[A]sub-t= -k*t +[A]sub-0

37

Half life of a reaction

T sub-1/2= 0.693/k

Or

T sub-1/2= ([A]sub-0)/2k

38

Arrhenius Equation

k= Ae^ ((-Ea)/RT)
Or ln(k)=ln(A)-(Ea/RT)

A=frequency factor, individual to each reaction
Ea=activation energy (in kJ/mol)
R= gas constant
T= temperature in kelvin

39

Activation energy

Energy that much be accumulated for the reaction to take plac

40

Activated complex (transition state)

The high energy state all molecules go through to go from reactants to products

41

Frequency factor (A)

Number of time the reactants approach the activation energy level per minute

42

Exponential factor

e^(-Ea/RT)
Represents a number 0 through 1 represents the fraction of molecules that have enough energy to participate in the reaction

43

Arrhenius plot

Linear equation that represents the relationship between the temperature and the 'k-value'

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

44

Arrhenius Equation (two point form)

Ln (k2/k1)=Ea/R*(1/T1-1/T2)

45

Collision Model

The reaction in question calls for an energetic collision between two molecules

46

Orientation factor (p)

Numerical representation of the angle at which the molecules must collide with one another for the reaction to occur

47

Collision frequency (z)

Number of particle collisions that occur per unit of time

48

K-value from Collision model

k=p*z*(exponentialFactor)

Write it out

49

Reaction mechanism

Series of individual chemical equations by which an overall chemical reaction occurs

50

Elementary step

The simplest possible step, chemical equation) into which an entire reaction mechanism can always be broken down

51

Law of elementary steps in reaction mechanisms

An entire reaction mechanism can always be broken down into one simple chemical equation that describes the entire process, known as the elementary step

52

Reaction intermediate

A molecule formed in an elementary step of a reaction mechanism but broken down by another reaction mechanism's elementary step

53

Molecularity

Number of reactant particles involved in a step

54

Unimolecular reaction

Only one reactant is required

55

Bimolecular

Two reactants are required

56

Reaction Order

Power 'n' to which the concentration is raised in the rate formula, determines the effect the concentration of that product has on the rate.
The 'n' in
Rate=k*[A]^n

57

Zero order reactant

Rate=k*[A]^0

The rate is independent of the concentration of that particular reactant

58

Reaction order for a catalyst

Always zero

59

Overall rates of reaction

Same as the rate of a reactant with a single coefficient

60

Individual reactant rate

Same as the overall reaction rate multiplied by its coefficient

61

Reaction rate when coefficient is multiplied

The rate is multiplied by that same value

62

Approximating reactant order

Graph- value=zeroOrder, linear=firstOrder, exponential=secondOrder

Algebra- [A]^x=OverallRate/k, x-is reactant order

63

Approximating k-value

k=Rate/[A]^x

64

When graphing concentration vs time

Use arhennious equations

[A](t)

65

Catalyst mechanism of action

Lowers the activation energy required for the reaction to take place

66

Activating energy from the k-value

Ea=[Ln(k)-Ln(A)]*(RT)

67

Reaction enthalpy ΔH

The net energy change when the reactants are transformed into products

68

Termolecular

Elementary steps in which three reactant particles collide,
Very rare to occur

69

Rate-determining step

The slowest step in the reaction mechanism

70

Activation energy in reaction mechanisms

Each require a little more energy, constant energy must be supplied