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MCAT chem > kinetics > Flashcards

kinetics Flashcards

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1
Q

kinetics

A

study of rates of reactions

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2
Q

activation energy (Ea)

A

kinetic energy required for reactants to collide in order for the reaction to occur

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3
Q

what does the rate of a reaction correspond to

A

how many collisions take place over a given time

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4
Q

Arrhenius Equation

A

K= Ae^(-Ea/RT)
k is rate constant

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5
Q

k in arrenius eqn

A

rate constant

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6
Q

a in arrhenius eqn

A

frequency factor
- frequency of collisions between reactants

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7
Q

Ea

A

activation energy

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8
Q

R is arrhenius eqn

A

gas constant

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9
Q

the rate constant can only be meaningfully affected by waht?

A

Ea and T

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10
Q

If Ea/RT decreases what happens to k

A

rate constant decreases

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11
Q

larger values of -(Ea/RT)

A

more negative, inverse relationship between Ea and K

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12
Q

lower EA

A

higher rate of reaction

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13
Q

temperature relationship to reaction rate (k)

A

proportional

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14
Q

Ea relationship to reaction rate

A

inverse

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15
Q

two ways to speed up a reaction

A
  1. reduce Ea
  2. heat up
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16
Q

what other ways is K impacted

A
  1. concentration of reactants
  2. pressure in gas rxn (increase pressure increases rate)
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17
Q

transition complex

A

brief period where covalent bonds in the reactants begin to weaken and bonds of products begin to form

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18
Q

Ea relationship to transition complex

A

Ea is the amount of energy needed to reach the transition complex

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19
Q

what is the highest energy point of the reaction

A

transition complex

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20
Q

are transition complexes isolatable?

A

no, too unstable

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21
Q

rate limiting step of a reaction

A

slowest step

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22
Q

x axis of reaction coordinate diagrams

A

progress of reaction (time)

23
Q

y axis of reaction coordiate diagrams

A

energy

24
Q

Ea on reaction coordinate diagram

A

difference in E between reactants and highest point

25
Q

∆G on reaction coordinate diagram

A

difference in E between reactants and products

26
Q

energy of P<R

A

exergonic and ∆G< 0

27
Q

endegonic reaction on reaction coordinate diagram

A

P energy > reactant
∆G>0

28
Q

∆G

A

thermodynamic constant for a reaction that cannot be changed by kinetic parameters
- decides spontaneity

29
Q

catalysts

A

substances that increase the rate of reaction by reducing the Ea

30
Q

how do catalysts decrease Ea

A

by stabilizing the transition state
weaken bonds in reactants and change orientation to increase frequency of collisions

31
Q

T/F catalysts can affect thermodynamic parameters

A

no. they do not change ∆G or sponteneity

32
Q

heterogeneous catalys

A

different phase than the reactant

33
Q

homogenous catalyst

A

same phase as reactant

34
Q

rate law

A

rate= K[A]^x[B]^y
- units of M/s

35
Q

order of a reaction

A

defined by the sum of the exponents

36
Q

zero order reaction

A

exponents of reactants sum to 0

37
Q

1 order reaction

A

exponents sum to one

38
Q

second order rxn

A

exponents of reactants sum to two

39
Q

third order rxn

A

exponents of reactants sum to three

40
Q

how to determine rate

A

look at changing concentrations to see how they affect the rate

41
Q

if the reactant is doubled and the rate is doubled what is the order

A

[A]^1

42
Q

if the reactant is doubled and the rate is quadroupled what is the order

A

[A]^2

43
Q

how to find K if you know the rates of both reactnats

A

K = rate/ [a]^x * [b]^y

44
Q

units of k for 0 order

A

m*s^-1 or m/s

45
Q

units of k for 1order

A

1/s

46
Q

units of k for 2 order

A

1/(m*s)

47
Q

units of k for 3 order

A

1/(m^2s)

48
Q

zero-order reactions

A

enzymes are saturated and there is too much reactant per enzyme
- catalyst is rate limiting step
- concentration of reagents is irrelevant

49
Q

first order reactions

A

radioactive decay and SN1 (depend on carbocation )

50
Q

second order raections

A

involve collision between two reactant molecules as in SN2

51
Q

second order raections

A

involve collision between two reactant molecules as in SN2

52
Q

rate law formula is based on

A

initial rate of the reaction

53
Q

graph of zero order rxn

A

linear

54
Q

graph of first order

A

non linear

MCAT chem (11 decks)

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