Elementary Reactions
elementary
reaction
reactions
mechanism
:
a
proposed reaction mechanism
of elementary reactions or steps that is believed
individual step
an
:
sequence
reactants
°
rate measurements
example
203cg ,
:
2
one
-
two
-
03
+
step
-
•
stoichiometric
elementary
molecularity
:
coefficients
reactions
a
of
number
Uni molecular reaction
:
Oz
Oz
+
+
Oz
t
O
O,
→
+
> adds →
O,
overall reaction
-
attacks
in
not used
produced
is
the overall
classified according
elementary
and consumed
to
during
a
reactant but does
chemical equation
for elementary
reactant molecules
an
O,
Oz
t
species that
are
are
mechanisms
some
→
Is
not appear
°
products
into
solar radiation
② I
:
as
step
① 03
reaction intermediate
place
:
02
→
eliminate
to take
302cg ,
→
mechanisms
→
a
transformed
are
be used to
can
in
reactions
molecularity
taking part
reaction in which
in each
single
a
step
species changes
reactant
into
products
molecularity
example
2
:
step
-
biomolecular reaction
an
→
termolecular
reaction
example
:
:
03
-
elementary
molecularity
an
of the
Oz
t
decomposition
ozone
→
Oz
reaction
in
t
O)
which
species
2
come
together
2
=
elementary
reverse
of
mechanism
( above
:
I
=
reaction
one
Oz
-
t
step
Oz
in
which 3 species collide
mechanism
→
03
of
+
ozone
03
simultaneously ( uncommon)
decomposition
Rate
Elementary
•
•
Uni molecular reaction has
a
biomolecular
a
laws
a
reaction has
molecularity
-
second order rate law
a
-
elementary
A
1
2
3
rate law
first order
rate law
reaction
→
products
rate
=
KEA ]
A
+
B
→
products
rate
=
KEAT [ B ]
A
+
A
→
products
rate
=
k [ A]
→
products
rate
=
KLATT B) To ]
→
products
rate
=
k [ A) 4- B ]
→
products
rate
=
k
At Btc
A
+
At B
At A
A
+
•
sum
of forward
reactions
=
overall reaction
•
sum
of
reactions
=
overall
reverse
[A]
reaction
reverse
'
'
experimental
rate law
(
example
:
2 NO cg
,
Oz Cg ,
+
→
,
NO ,
NO
→
→
NO
+
Nz Oz
( reverse )
+
Nz Oz
formation
rate
NO
consumption
rate
K
2
Oz
( slow ignored ) ( reverse )
NO ,
,
of formation of
a
-
1- NO ] [ Oz ]
Kr
=
consistent with
NO
net rate
of formation of
Rate
1
Step
Step
2 NO
t
t
Nz 02
NO
species
:
→
z
NO ,
→
Nz Oz
formation
Oz
t
the rates of all
of
sum
consumption
NO ,
+
formation
minus
of
any
Nz Oz
of
of
of
N > Oz
of formation of NO
,
=
2K , ENZO ] [ Oz ]
net rate
of formation of
Nao ,
=
( from step
,
T
2 NO ,
k ENO ]
'
,
-
formed
in
-
k
'
,
molecules
TN
,
O, ]
-
-
①
removed in O
'
are
formed
K , [ Nz 025102 ]
removed
in
②
k ENZO
'
,
=
=
,
]
K , TN 2021502]
KIEN 0212
resulting
reactions
reactions
lead to its consumption
rate
=
'
reverse reaction
Nz Oz
elementary
K , 1- NO ]
=
Nz Q
for
rate
rate
elementary
the rates
'
of
proposed ?
2
)
in
that
its
steady
-
state
approximation
the assumption that the net rate of formation of
:
→
K , 1- NO ]
.
.
now
,
can
the intermediate
'
'
find
-
k
concentration
'
,
[ Nz Oz )
of
[ Nz Oz )
sub
proposed
to
•
not the
same as
forward
→
in
step
K
Nz Oz
'
,
the
2
>>
is
k
.
that it reacts
[ N > Oz ) [ Oz )
as
soon
intermediates
as
it
is O
formed
is
0
=
,
k [ NO ]
'
,
=
k
'
k [ Or ]
t
,
,
,
of formation of
rate
.
rate law
so reactive
is
-
reaction
NO
experimental
very slow
Kz [ Oz ]
when
,
2K ,
=
,
k
N , O, ] [ O, ]
( rate of formation of
one
so
[
'
,
ENZO , ]
[ Nz Oz ]
is
Ss
=
2K , Kal NOT [ Oz ]
k
'
,
t
k , [ Oz ]
-
NO ,
=
Kr [ NO ] [ Oz ]
Kz [ Nz 02h50 ]
,
cancelled
-
.
.
:
rate
of formation of
agrees with experimental determined
Kr
2K ka TNO ) TO , ]
,
NO ,
=
rate law
2k kz
,
=
k
'
,
K,
'
-
ka -102 )
is
ignored