Unit 2 (chp 16, 17, 18.1 + 18.2) Flashcards
(132 cards)
1
Q
define CHEMICAL KINETICS
A
study of rxn rates & their factors
2
Q
define RXN RATE
A
change in concentration sof reactions/products as function of time
3
Q
list factors of rxn rate
A
- concentration
- physical state
- temperature
4
Q
for a rxn to occur, there must be a ___ collision energy
A
minimum
5
Q
an __ in surface area increases the rxn
A
increase
6
Q
how does an increase in concentration affect collision
A
increase particle collision
7
Q
how does an increase in temperature affect collision and why
A
increase particle collisions bc of increase in energy
8
Q
what is the formula for reaction rate
A
-(change in concentration)/(change in time)
9
Q
why is the change of concentration negative in the formula for rxn rate
A
to make it a positive rate
10
Q
if reactant concentration decreases, then the product concnetration
A
increases
11
Q
the rate number depends on the _____ in the balanced equation
A
reference substance
12
Q
rate of rxn is always
A
positive
13
Q
rate of change is also considered the
A
slope
14
Q
rate law occurs at a __ temp
A
fixed
15
Q
the rate constant (k) is specific to ___
A
temperature
16
Q
how are m & n in rate law determined
A
experimental values
17
Q
t/f: m & n in the rate law formula are related to the coefficient of a balanced chemical equation
A
false, they are not related
18
Q
what do m & n in rate law formula describe
A
how rate is affected by a reactant’s concentration
19
Q
in __ order, the rate doubles when the concentration doubles
A
first
20
Q
in __ order, the rate quadruples when the concentration doubles
A
second
21
Q
in __ order, the rate does not change when the concentraton doubles
A
zero
22
Q
how is the overall rxn order found
A
m + n
23
Q
the half life of a first order reaction is
A
constant
24
Q
the half life of radiactive decay/nucleus is an indicatory of ___
A
stability
25
the half life of a second order rxn is __
inversely proportional
26
the half life of a zero order rxn is ___
directly proportional
27
define COLLISION THEORY
particles have to collide to react
28
according to collision theory, an increase in concentration reactant increases the ___ which increases the ___
collision frequency; rxn rate
29
how do you calculate the number of collisions in a rxn
multiple the coefficients of the products and reactants
30
effective collisions __ bonds to form the __
break; product
31
what two factors reduce the number of effective collisions
activation energy & molecular orientation
32
define ACTIVATION ENERGY
energy threshold colliding molecules exceed to react and achieve the transition state
33
delta H of rxn is equal to
(activation energy of fwd rxn) - (activation energy of rev rxn)
34
define EFFECTIVE COLLISION
collision with enough energy and relative orientation to break bonds and form products
35
define ORIENTATION PROBABILITY FACTOR
ratio of effectiely oriented collisions to all possible collisions specific to a rxn
36
oreitnation probability factor is related to ____
reactant complexity
37
a more complex reactant has a ___ orientation probability factor
decreased
38
define TRANSITION STATE
state where unstable species w/partial bonds halfway between reactants and products
39
aka transition state
activated complex
40
t/f: the transition state can be isolated
false
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the transition state is at the point of ___ energy
max
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deifne RXN ENERGY DIAGRAM
diagram plotting how potential energy changes as rxn goes from reactants to products
43
how does temperature affect rate
exponential increase
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how does temperature affect collisions, rate constant, and rate
1. increase in temp --> more collisions
2. --> larger K
3. increased rxn rate
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how does temeprature affect particle kinetic energy
increase
46
define COLLISION ENERGY
fraction of collisions w/energy greater than or equal to activation energy
47
how does a lowered activation energy affect collision energy, K, and rxn rate
1. lowered Ea --> higher collision energy
2. --> higher k --> greater rxn rate
48
how does an increase in temperature affection collision energy, K, and rxn rate
1. increase temp --> increase collision energy
2. --> higher K --> greater rxn rate
49
what is the purpose of the ARRHENIUS EQUATION
shows exponential relationship between temperature and rate constant
50
define FREQUENCY FACTOR
product of collision frequency and orientation probability
51
aka frequency factor
pre-exponential factor
52
define RXN MECHANISM
sequence of single rxn step
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define ELEMENTARY STEPS
individual steps of rxn characterized by molecularity
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define MOLECULARITY
number of reactant particles in rxn
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the rxn order of elementary steps are its
molecularity
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how many reactants are in a unimolecular elementary step
1
57
how many reactants are in a bimolecular elementary step
2
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how many reactants are in a termolecular elementary stetp
3
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define RATE DETERMINING/RATE LIMITING STEP
slowest step in rxn
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the overal rxn rate law is the rate law of the
rate determining step
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the rate determining step only involves reactants
before/during rate determining step
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define RXN INTERMEDIATE
substance formed in 1 step and used in another
63
define MECHANISM
hypothesized model of rxn with 3 criteria
64
list the 3 criteria of a mechanism
- elementary steps add up to overall balanced equation
- elementary steps involve 1 or 2 reactant particles
- must correlate w/observed rate law
65
define CATALYSTS
substance lower activation energy which increases K and rxn rate
66
t/f: catalysts allow rxns to yield more product
false, they increase the speed of rxn but not the yield
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define HOMOGENOUS CATALYST
catalyst that is same phase as reactants
68
define HETEROGENOUS CATALYST
catalyst that is different phase than rxn mixture
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define ENZYME
protein catalyst where substrates bind to its active site
70
a rate constant equals
k2/k1
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how do you know which order a rxn is based off its graph
select the order that produces a linear graph
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define KINETICS
speed of [products] or [reactants] appear/disappear per unit of time
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define EQUILIBRIUM
amount of [product] appeared after unlimited amount of time/once no further change
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define EQUILIBRIUM STATE
[product] and [reactant] don't change bc forward rxn equals the reverse rxn
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t/f: in an equilibrium state, all rxns are reversible and will reach this under proper conditions
true
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define CHEMICACL EQUILIBRIUM
rxns occur at same rate equals no net change
77
what is the formula for equilibrium
(fwd rate) = (rev rate)
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t/f: equilibrium equals kinetics
false, concentrations differ even if the rates are equal
79
define the EQUILIBRIUM CONSTANT
ratio of [product] over [reactant] for reaction to be equal
80
what does it mean for a rxn to be at equilibrium
forward and reverse rxns are equal
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what products and reactants should be considered when calculating the equilibrium constant
aqueous and gaseous
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a small Kc is favorable to
reactants
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a large Kc is faborable to
products
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what does it mean to have a small Kc
there is little product created before equilibrium
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what does it mean to have a large Kc
there is a lot of product made before equilibrium
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define REACTION QUOTIENT
[product] over [reactant] at any point in the rxn
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what does the reaction quotient describe
how close and direction to equilibrium
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t/f: a rxn has the same equilibrium state regardless of the initial concentration
true
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what is the relationship between Q and K at equilibrium
Qc = Kc
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K is like the __ but Q is like the __
destination; distance
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define HETEROGENNOUS EQUILIBRIUM
equilibrium but reactants and products are in different phases
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why are solids and liquids ommitted from expressions for Q and K
always have same concentration as products and reactants
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t/f: K can only be expressed using molarities
false, it can be expressed using partial pressures
94
why can K also be written using partial pressures
partial pressure is directly proportional to molarity
95
if the moles of gas don't change in a rxn then what is the relationship between Kp and Kc
Kp = Kc
96
describe the effects of the reactants and products when Q < K
reactants increase & products decrease
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describe the effects on the reactants and products when Q > K
reactants increase and products decrease
98
describe the effects on the reactants and products when Q = K
no net change
99
when should X([A reacting]) be neglected
([A initial]/Kc) > 400
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define LE CHATELIER'S PRINCIPLE
when disturbed, the chemical system goes through a net rxn that decreases the effect of disturbances
101
what are the 3 common disturbances in Le Chatelier's principle
- change in concentration
- change in temperature
- change in pressure (bc change in volume)
102
t/f: catalysts effect kinetics and equilibrium position
false, catalysts only affect kinetics
103
what does it mean for equilibrium to shift to the right
more product is created
104
what does it mean for equilibrium to shift to the left
more reactant and less product
105
an increase in [reactant] causes the equilibrium position to shift
to the right
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a decrease in [reactants] causes the equilibrium position to shift
to the left
107
an increase in [products] causes the equilibrium position to shift to
the left
108
an decrease in [products] causes the equilibrium position to shift to
the right
109
an increase in pressure (and decrease in volume) causes the equilibrium position to form
fewer moles
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a decrease in pressure (and increase in volume) causes the equilibrium position to form
more moles
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an increase in pressure with the addition of an inert gas and constant volume causes the equilibrium position to
not change
112
which disturbance affects K
change in temperature
113
an increase in temperature causes the equilibrium position to shift toward
heat absorption
114
a decrease in temperature causes the equilibrium position to shift toward
heat release
115
if the temperature increases and the delta H of rxn is > 0, K
increases
116
if the temp increases and the delta H of rxn is < 0, k
decreases
117
if the temp decreases and the delta H of rxn is > 0, k
decreases
118
if the temp decreases and the delta H of rxn is < 0, k
increases
119
define an ARRHENIUS BASE
has OH in the chemical formula and dissociated into OH- in water
120
deifne an ARRHENIUS ACID
has H in chemical formula and dissociates into H3O+ in water
121
define a BRONSTED LOWERY ACID
donates H+
122
define a BRONSTED LOWERY BASE
accepts H+ bc of lone pair of e-
123
an acid base rxn is also referred to as a
proton-transfer process
124
__ is amphiprotic
water
125
bronsted lowry acids turn into
conjugate bases
126
bronsted lowery bases turn into
conjugate acids
127
define AMPHIPROTIC
acting as either acid or base
128
what is the only difference between an acid/base and their conjugates
number of hydrogens
129
a stronger acid becomes a __ conjugate base
weaker
130
a stronger base becomes a __ conjugate acid
weaker
131
what does the direction of acid and base rxns depend on?
acid and base strength
132
what formation of conjugate bases and acids are favored in acid-base rxns
formation of weaker acids and bases
