before we start let me tell you
we'll be covered in the exam the second
midterm on Saturday this Saturday
chapters included our nine eleven twelve
and fourteen chemical kinetics is
included but equilibrium is not included
okay I guess chapter 414 is chemical
kinetics so nine eleven twelve and
fourteen that makes about nine eleven
twelve and fourteen four chapters clear
now we there had been questions about
like the chapters that you skipped
actually we haven't skipped those
chapters we left them to you to read and
learn for example chapter ten is was
about gases so we assume that you know a
lot of things about the gases from high
school but I will advise you to read it
from the book again that means if there
is any problem related to the gases that
may be actually not directly related to
the gases but you have to know basic
knowledge about the gas behavior gaseous
state to solve that problem and you need
to know that so please be prepared
accordingly as a matter of fact okay
let's see this Friday Thursday we have
one hour lecture right in the afternoon
and Friday in the afternoon I will be in
my office so if you have any questions
before the exam anything that you would
like to ask me please drop by I will be
there okay all right let's continue
remember last time we were talking about
the chemical kinetics and the rate of
chemical reactions
and we said that the rate of a chemical
reaction actually speed of the chemical
reactions are given by the changes of
molar concentrations of reactant or the
product and when we express the
dependence of the rate on the molar
concentrations of this reactant that is
called the rate law so the rate law
tells you again the relationship between
the rate and the molar concentration of
the reactant as a matter of fact and we
have a rate constant there which is
specific to the reaction of reaction and
as long as the temperature is constant
rate constant is the same when the
temperature changes then the rate
constant also changes now again
depending on the dependence of the molar
concentrations of the reactant overall
rate law we classify the reactions as
first order second order or third order
reactions again we said that the third
order reactions are very slow very very
slow we usually do not consider that it
doesn't take it appreciate way that we
just assume that the third order
reactions but there is also zero order
reaction remember where the rate of the
reaction is independent of the
concentration is off the reactant and
this is only the case when you have
reactions taking place at the surface of
a solid so for example if a gases
reaction that taking place at the
surface of the solid when all the
surface of the solid is covered by the
gas molecules adsorbed gas molecules
it's full and as soon as one molecule
reacts there another gas comes out and
again covers the surface of the simply
solid in that case the rate is
independent of the concentration and we
call that kind of reaction as
reaction now by considering those first
order second order and zero order
reactions we have derived the equation
which relates the concentration of the
reactants to time actually and those are
simply called the integrated rate law
remember those are very very important
again to calculate the concentration of
any reactant or any product after
whatever time passed from the beginning
of the reactions as a matter of fact
that means that the rate integrated rate
law gives you the relationship between
the concentration of the reactant or the
product and the time and again you have
to know the rate constant now in other
things we have defined from that
integrated rate law half-life of a
chemical reaction so the half-life of a
chemical reaction is simply means the
time required to react half of the
initial reactants that means if you
start with a point two molar
concentrations of your reactant and the
time required to get the concentration
to 0.1 which is half of the initial or
the beginning concentration that time is
called the half-life of chemical
reactions and the half-life of chemical
reaction for the first-order reaction
again was independent of the initial
concentration but the half-life of the
second and the zero order reactions
depends on the initial concentrations of
the reactants two so we have seen all
those now today we will look at again
factors that affect the reaction rate
and let's see the first is temperature
second is frequency of collusions again
this is how many collisions are taking
place per second in the reaction mixture
reaction medium and the third is the
orientation of the molecules we will
talk about these each
but they again this is simply means
there's every collusion even though the
molecules have enough energy do not
yield the product they collide and then
come back they separate again and no
products are actually taking place and
why because the orientation of the
molecules when they collide is not
proper is not right for that reaction
reaction doesn't take place right so for
example suppose that the molecules these
are the molecules if the molecules
collide like this and if they have
enough energy then they can simply this
collusion may yield the product but if
the collusion is not this way but the
collusion is like this the molecule
actually that collusions will not yield
the product that means there will be no
chemical reaction so this is what it
again orientation of molecules when we
say the orientation of molecules that
means orientation of the molecules when
they collide is a factor determinant
whether the reaction will take place or
not now the last one again here the
energy needed for the reaction to take
place that means that when the two
molecules collide to react they should
have enough energy to go to the product
there is a threshold actually they have
to go over that and to have get over
that threshold they should have a
minimum energy actually and that minimum
energy is called the activation energy
activation energy so again you see not
all collisions will yield the product
only those collisions that have enough
energy at least equal to the activation
energy or greater will lead the product
yes
we can't I mean we can't take the
molecules and play with the molecules no
but when considered like different
shaped molecules right they may be
collusions like this they may be a
collision like this they may be a
collision like this all are possible
only those collisions which have proper
orientations will yield the product okay
that means we can't control the
orientation of the molecules when they
collide let's put it that way okay
now so these are the factors
let's go these in more details here
again the temperature and the rate
generally as the temperature increases
rate increases why because the rate
constant is temperature dependent first
of all now second when you increase the
temperature that means that the average
kinetic energy of the molecule increases
what does that mean that means more
molecules will have activation energy or
greater than that as the temperature
increases
what does that mean that means more
collisions will lead to the product
right because I have more collisions
with enough energy when I increase the
temperature again this is a general I
will give you the relationship between
the temperature and the activation
energy and the rate constant rate
constant doubles with every 10 degree
centigrade this is again approximate
right it's not exactly equal but
approximate but what did that means
increasing the temperature always
increases the rate of chemical reactions
there are two things first increase in
the kinetic energy of the molecules
average kinetic energy and second wave
constant increases again at the same
time all right now here are shows you
two reactions I guess these are just the
nail
Iren rusting in water acidic solutions
in hot water
you have faster reaction in cold water
is slower reactions again yeah
frequency of collusions collusions
actually the collusion model is based on
the kinetic molecular theory
molecules must collide to react as we
said they have to simply that's what
collusion model is molecules should
collide to react so if there are more
collisions more reaction can occur that
means higher frequency of collusion
means more collisions are taking place
per unit time let's say per second so
higher collusion frequency means more
collisions that means faster chemical
reaction so if there are more molecules
the reaction rate is faster now this
more molecules means what higher
concentration right higher concentration
so more molecules and more collisions
per unit time faster reactions here
again also if the temperature is higher
molecules move faster as we said causing
more collisions and higher rate of
reaction more collusion with enough
energy that means activation energy and
greater that's what it means again now
collusion model in a chemical reaction
bonds are broken and new bonds are
formed this is again a chemical reaction
almost every chemical reaction there is
some bonds are broken and new bonds are
actually forming now molecules can only
react if they collide with each other
that's in other things they have to get
together so that the some bonds will
break and the other bonds will start
making that point is called the
transition state transition state so
second is the orientation of again this
is another reactant we will talk about
that transition state but the other
orientation orientation of the molecule
as I explained molecules can often
collide without forming products sure
there will be not all collusions leads
or yields product we have to know that
for example maybe like twenty collusions
out of hundred or less may lead to the
product but the others do not align in
molecules properly can lead to chemical
reaction this is that doesn't mean that
we can align them by using you know some
it is we can't do that as
matter of fact bonds must be broken and
made and atoms need to be in proper
orientations proper orientation this is
the chemical reaction for example now
the chemical reaction you see again cl2
is formed and chlorine and nitrosyl
chloride these two chlorine atom and
nitrosyl chloride molecule should
collide but if the collusions is from
the nitrogen side like here no product
will form even though the molecules have
enough activation energy that really
doesn't take place but the if the
collisions are taking place from the
chlorine atoms side of the molecule then
the product simply takes place this is
what we mean by the orientation of the
molecule but again remember we can't
really design them to orient properly
and lead to the reaction because
molecules are moving freely we can't
control that
okay now energy needed for reaction to
take place activation energy this is
again very important and if the
colliding molecules have enough
activation energy have enough energy
that means in the form of kinetic energy
or whatever all the other energies then
they can simply lead to the chemical
reactions to the product actually lead
to the products so here is again an
analogy how we understand the activation
energy so the minimum energy needed for
the reaction to take place is called
activation energy minimum energy if the
molecules have greater energy they will
definitely react greater energy than the
activation energy an energy barrier must
must be overcome for a reaction to take
place much like the ball must be hit to
the O to overcome the barrier in the
figure below this is like you know if
you hit the molecule there golf-playing
the goals if there is a hill here a
little bit like that so you have to
really heat it with enough power and
give enough energy to that ball so that
it will go over this hill here if the
energy is less than to get over this
hill means the ball may
probably come up here and then we'll
come back but that corresponds to no
reactions as a matter of fact but if the
ball comes out that way that corresponds
to probably the reaction products are
simply forming ok now transition state
as I said the activated complex
reactants gain energy as the reaction
proceeds until the particles reach to
the maximum energy state now this is
simply means like when you have two
molecules are simply getting closer
together right getting closer together
there's electrons and so on there's
going to be some repulsions between them
right and what does that mean that means
that their potential energy will
increase right now the as the molecules
getting together colliding their energy
kinetic energy is converted to their
potential energy and that potential
energy in fact if enough to get that
over that hill then the reaction and the
product will take place and that state
at the top there is called the
transition state and the reactants at
that transition state are different than
reactants and the products in terms of
chemical chemistry or chemical point of
view so acting at the transition state
when the two molecules get together and
they just start reactant to lead to the
product that's called activated complex
activated complex and the lifetime of
that activated complex are very very
short actually and that is activated
complex and that is also called the
transition state the energy needed to
form this state is called the activation
energy that's again you get that
activation image from the kinetic energy
of the molecules as I said the kinetic
energy is converted to the potential
energy and the energy goes up and
reaches to the transition state actually
now here is the example this is the
isomerization of the nitrile and assira
nitrile I so nitrile and Assyria nitrile
and what we have there is actually we
have
this one is called iso nitrile and that
simply goes to h3c why I can't write it
and see and triple bond n this is
nitrile and this is a seat
ISO nitrile iso nitride these are called
isocyanides also I shouldn't say nice so
what what what really happens there is
you see again the starting over here
this is the average sort of average
kinetic energy or energy of the
molecules if the molecules have enough
energy and the potential energy that
energy will be converted to the
potential energy potential energy will
increase and increase and increase and
it will reach that point that point is
called the transition state and the
complex there is called the activated
complex activated complex what is the
form of the molecule here again what
really happens as you go from reactant
to the product this bond is broken and
then new bond between that carbon and
this carbon takes place so the
activation state right over here this
ch3 C methyl group here sort of this
carbon binds here a little bit and
they're a little bit this bump simply
breaks up and that new bond forms and
the product comes out like this
so again you see this is what I said the
activated complex and in terms of
chemical standpoint it is different than
the reactant and it's different than the
product also it's just sort of
intermediate between the reactants and
the product okay in this graph this is
called the energy profile of a chemical
reaction graph and the graph is called
energy profile this is called
reaction coordinate or reaction progress
that means as the time goes on simply to
the molecule in this case the since
there is no collusions potential energy
kinetic energy of the molecule is
converted to potential energy reaches to
there and comes down here and this
energy here that means the average
energy sort of off the reactants and the
transition state is called the
activation energy that's called the
activation energy and now this Delta e
is actually the Delta e of the chemical
reaction internal energy of the chemical
reactions if you give that in terms of
Delta H you can also say that that's
equal to the Delta H of the reaction
this is the energy of the reactants at
the beginning this is the energy of the
product the difference here is Delta e
which is the internal energy of change
of the reaction now is this reaction
exothermic or endothermic yes
exothermic right because that much
energy will be released to the
surrounding as the reaction goes from
reactant to the product but there are
cases where that the energy of the
product is higher than the energy of the
reactant in that case the internal
energy change would be equals to the
energy absorbed by the system means the
reaction is endothermic endothermic so
we may have endothermic or exothermic
and the shape of the energy profile for
the reaction will change as I explain
you now if you go from the reverse side
that means if you start with the product
I saw nitrile as we will see in a
chemical equilibrium I see the nitrile
this is actually a suit a nitrile I
can't all right a co nitrile then the
reaction will be from this side to that
side if you look at the reaction from
that direction again the activation
energy for the reaction from here to
there will be equal to this actually
right so that's equal to the activation
energy as a matter of fact so you see
again for the forward reaction
actually we can simply take the
activation energy between the energy of
the reactants and the activation
activated states for the others it will
be over here and the from the reverse
side in this case if that reaction will
be endothermic reaction and Delta e is
actually added to the eg with an eg as
we see internal the activation energy so
let's look at here plots are made to
show the energy processed by the
particles as the reaction proceeds over
here at the highest energy state the
transition state is formed this part
right there and reaction can be
endothermic or exothermic as we
explained the shape of the curve energy
profile will change now distributions of
the energy of the molecules again is
given by plots like this at any given
temperature so now at higher
temperatures the average kinetic energy
of the molecules is higher compared to
the lower temperatures so if the
activation energy for a reaction is this
for example what does that means that
means at higher temperature we will have
more molecules which have activation
energy or greater than that that means
that the rate of the reaction will be
higher in higher temperature rates will
increase as the temperature increases
alright now the relationship between
activation energy temperature and rate
constant this is what I was telling you
and that reaction that that equation
actually here given this K this is the
rate or rate constant of the reaction
equals to a times e to the EA activation
energy divided by RT this equation is
called our Henny's equation
- equation right so now activation
energy can be determined graphically by
recognizing the equation this we can
simply take the natural
logarithm both sides of the rme's
equations and we you can put the
Arrhenius equations in logarithmic
natural logarithmic form in this way Ln
K will be equal to the activation energy
divided by RT plus Ln a again if we know
the rate constant at different
temperatures then we can make this plot
here and from the slope of this plot we
can determine the activation energy of a
reaction activation energy of reaction
but what we need for this at least
actually two or more rate constant at
different temperatures right different
temperatures as a matter of fact so if
we have for example two rate constants
at two different temperatures we can
combine those two equations or Henny's
equations and we can obtain this
equations and this is very useful again
ln k1 over k2 natural logarithm is equal
to EA over r 1 over t2 minus 1 over t 1
usually I take that as minus sign over
here and make this as put that k2 up
there actually and so on but you know
from that you can just get that and
follow the correct science so what does
this means this simply means that if I
know the rate constant of reaction at
two different temperatures at T 1 K 1 T
2 k2 then I buy using this without the
graph actually draw in the graph I can
calculate the activation energy right or
if I know the activation energy of a
chemical reaction and if I know the rate
constant at one temperature I can
calculate the rate constant at any
temperatures right just put in the
values here and we can simply calculate
that ok
now let's let's come down here I have
yeah I guess I will I should be here why
not all right right this is this problem
here I picked it up from the book I just
added this deal
d was not there I add that actually now
this is the chemical reaction right here
urea and urea the formula of that is
actually like this why what is wrong
button with my chalk I mean I can't
write it this is the urea molecule
actually there
this one the open form of that is this
way reacts in acidic solution to form
ammonium cation and carbonate ion
bicarbonate ion this is hydrogen
carbonate ion as a matter of fact the
reaction is first order in urea and
first order overall now what does that
means that means the rate law for this
reaction would be as follow rate is
equal to K times the concentration of NH
2 co and H 2 like this this is the rate
law of the reaction right because the
first order in terms of with respect to
the concentrations of urea and first or
overall means this is the first order
reactions now it says the ammonium the
urea concentration is equal to 0.2 zero
zero the rate measured at sixty one
point O five is eight point five six
times ten to the minus five that's the
data given what is the rate constant
what is the rate constant we can easily
determine that rate constant again by
using this equation here right so the
let's say the rate is given as 8 point
56 times 10 to the minus 5
now per mole per second and this is
equals to K times and the concentration
of urea again when we obtain that rate
was point two zero zero this means point
two zero zero molar and what is K K is
equals to simply eight point 56 times 10
to the minus five divided by 0.2 0 zero
and that will be equal to the rate
constant let's see what I have simply
calculated here yes that is for 28 times
10 to the minus 4 second to the minus 1
that is again the unit here the units
are important I guess in this exam we
will probably require you to write down
the units of the answer that you
calculate it usually in fact the numbers
that we get always have units with them
so the unit are important this is the
rate constant there now the second one
it says what is the concentration of
urea in this solution after for 10 to
the 3/4 are actually that's 4000 seconds
if the starting concentration there is
0.5 0 0 molar hmm now here you see again
we asked to calculate the concentration
of the reactant after a certain time we
have to use the integrated rate law for
the first order reaction right so what
is the integrated rate law for the first
order reaction and that is ln simply a
over a0 and equals to minus K times T
like this or you can get that to the
other side and so on now
what we simply know here that the a
initial concentration it says if the
initial concentration is 0.5 0 0 molar
and this is 0.5 0 0 molar and we know
the time also time is equal to 4 0 0
times 10 to the 3 second like this now
again this is at the same temperature do
we know the rate constant yes we know
the rate constant right there so by
using that we know the rate constant we
know the actually T we know that value
and we can calculate the concentrations
of a and the concentrations of a that I
have calculated actually concentration
of let's say a here turns out to be as
0.090 3 molar so this is the answer for
B actually after 4,000 seconds actually
concentrations of the initial at urea
actually it would be equal to this now
it is always a good custom to check your
answer use your logic and see if it is
logical the answer is now sometimes you
may get an answer here which will be
greater than 0.5 right it is possible or
you may just do an error somewhere put
it in the right you know instead of
putting it
nominator put in denominator and so on
so this is logical again at least
logical in terms of what it is less than
the initial concentration you know if it
is greater than issue of concentration
that case you have done something wrong
so please make that little check and
again when you get the number of the
answer as a matter of fact now the beads
no see it says what is the half-life for
this reaction at 60 1.05 degrees
centigrade we can find it out because we
know that from this actually we know
that the t 1/2 for the first order
reaction
for the first order reaction is equals
to Ln natural logarithm of 2 divided by
K and if you take that K value is given
Ln 2 and you can calculate the half-life
and the half-life turns out to be 16 20
seconds 1620 second this is our
half-life again answer to the C now this
is I added it there right and again it
involves using our Hennis equation or
Hannah's equation that equation I gave
you remember D which gives you the
relationship between the rate constant
and the temperature and the activation
energy of the reaction this is the or
Hennis equation again and when we simply
take that natural logarithm of K is
equals to minus e activation energy
divided by RT and this becomes plus Ln a
now remember this is our hennas constant
this is constant at a given temperature
like this so from there we have this
form for two different temperatures
let's say Ln K 2 divided by K 1 at
temperature 1 and temperature 2 equals
to minus EA over R now here 1 over T 2
minus 1 over T 1 this is what I was
trying to tell you like if I put this
make this ratio as k2 over k1 then I can
make that as minus sign here about the
first one is 1 over T 2 minus 1 over T 1
here now what we need to do here just
put the values and calculate the
activation energy again we know the K 1
and we know K 2 again at 70 105 degree
centigrade
then we know our R is constant and the R
is simply equals to 8.314 joules per
mole per Kelvin like this and the other
things here we have to be careful when
we use temperature in equations the unit
always has to be in Kelvin right so
those degrees centigrade Celsius units
has to be converted to the Kelvin and
you have to put it there
remember again to convert it to Kelvin
you just add 273 point 15 right and then
you just put the values everything is
known except the activation energy and
the rest is actually math activation
energy that I have calculated you can do
it yourself is equal to 75 point 75 75
point 75 kilojoules per mole okay so
this is how we simply work with the
kinetics problem using in fact different
equations our Hennis equations and so on
actually by using this our Henny's
equation for two different temperatures
and different rate constants depending
on whatever unknown you can determine it
right suppose you know the temperatures
activation energy and the one off the
rate constant you can determine the rate
constant at any given temperatures if
the rate constants are given activation
as these are given one temperature is
given you can calculate the other
temperature corresponding to the second
rate constant so on I mean just just
mathematical equations you can use it in
different way to calculate whatever
asked actually right just have to
rearrange the things and look what
the values there and put them in a
correct units the unit is also very
important because if you put here
degrees Celsius instead of Kelvin unit
right the answer will be wrong and again
if you take the value of R as 0.08 to
Oleta atmosphere and so and so the
answer will be wrong right so when
you're dealing with equations that have
energy in it R has to be taken in units
of energy in joules actually it's 8.314
I think joules per mole per Kelvin okay
now let's look at here what does it says
Lowe's versus theory let's read this
kinetics gives what happens okay we call
the description the rate law that means
we describe the rate and the rate law
describes the reaction that's what he
says I guess I don't like this sentence
over here but it's okay why do we
observe that rate law we explain with
the theory called mechanism now remember
the mechanism was the details of how
reactants are converted to the products
in a chemical reactions when we write
down a chemical reaction it doesn't
usually takes place as it is written
there if there are two reactants
actually the reaction doesn't take place
usually those two molecules colliding
and given the product no there are other
steps between the reactant and the
product and usually these are series of
chemical reactions chemical reactions
and these chemical reactions the set of
these chemical reactions actually called
the mechanism of chemical reaction now
why the mechanism is important first of
all we know more things about the
chemical reaction how the chemical
reaction is taking place now
what is forming what is reacting what
kind of activated complex and so on but
second again if we know the rate law of
a chemical reaction we can propose a
mechanism for the chemical reactions
which fits the rate law or vice-versa if
I know the mechanism of a chemical
reaction then I can write down the rate
law for that reactions so you see again
the rate law and the mechanism means the
series of the reaction that taken place
between the reactants and the products
are related to each other as a matter of
fact now let's make an exhibit a series
of stepwise reaction that show how
reactants become products now another
things here I have to probably remind
you we haven't suppose that I have a
reaction like this to a plus B going to
C plus D like this now the rate law for
this reaction cannot be written directly
from the chemical equation balanced
chemical equations okay I can't really
say that the rate law for this reaction
is equal to K times concentration of a
since I have the coefficient to 2 and
times B and know this is not correct it
may but I can't really write it by
looking at the balanced chemical
equation for the chemical reactions so
what that simply means that the
coefficients in front of the reactants
are not as the exponents of their
concentrations in the rate load no so
how can I write down the rate law I have
to do the experiments remember I have to
simply do serious
of reactions at different concentrations
of the reactants and find out how the
rate depends on the concentration when
you increase double the concentration
remember as I said if the rate doubles
means that the exponent of the
concentration here is 1 now if it is
quadruples that means it is true and
this way I simply by experimentally I
determine the rate law of a chemical
reactions I can't write it directly by
looking at the balance equation we have
to remember that we never do that but if
I know the mechanism then I can simply
write down the rate law as we will show
you but in other things the reactions
which we call the mechanism are all one
step reactions one step reaction means
this actually if I know that this is a
one-step reaction what does that means
that means to a molecules and 1b
molecules collide with each other and
then the product C and D forms this is
one one-step reaction actually now if I
know that the this reaction in one step
then the rate low I can write down the
rate or rate law will be equal to that
but if I don't know that the reaction is
one-step reaction again I can't write
down the rate law I have to do
experiment to determine it
experimentally so all the steps in the
mechanism
those are reactions between reactant and
the product steps are one step mechanism
actually one step reaction is what does
that means that means that by looking at
their chemical reaction balance chemical
reaction I can write down the rate law
let's look at what this simply means I
guess here here is now you see again
these are all one step elementary they
are called elementary reactions or
one-step reaction elementary one-step
reaction and it
it is this kind like this we call it
Union molecular and what does that mean
that simply means that the molecule
actually decomposes to form the product
as a matter of fact whatever the product
is and the rate law for this reaction
will be equal to K times concentrations
of a how why why I can write it directly
by looking at there because it is
elementary reaction one-step reaction
and then a mental reaction one-step
reactions in fact I can write down the
rate law by looking at the balance
chemical equations and these are usually
the reactions that is in the mechanism
or that makes the mechanism off the
chemical reactions as a matter of fact
and this is called uni molecular now by
molecular if I have like a a product
they simply collide with each other or a
be collide with each other one step
elementary reaction to form the product
then the rate will be equal to K times
the concentration of a times
concentration of B I don't have the if I
have here two for example then I would
have put it here too because the
elementary one-step reaction but
remember termolecular reactions are very
seldom and very very slow we don't
really consider those but there are
cases here as we will see now this is
the biomolecular by molecular means that
two reactant molecules to reaction
molecules collide with each other and
the product forms that's all it is now
termolecular involves the collisions of
three molecules at the same point at the
same time in three-dimensional space
right and the probability of happening
that is very very low so what does that
means that means that the rate of the
termolecular reactions are very very
slow and we just neglect them usually we
neglect them very
where we have the turbo liquid reaction
but you see again even this case since
it is elementary reaction we can write
down the rate low as K times a to the
third because we have three of those
three a goes to the product and this one
will be to a be actually like this then
it is equal to this and so on again as I
said I said that this we can't write it
by looking at this because we don't know
whether it's a one-step reaction but if
you know it's a one-step reaction
elementary reactions we can write it
here and that's the exactly written here
like this and another termolecular
three of those again KABC see again 1 1
1 like this so these are simply called
molecularity of the elementary reaction
what does that means how many molecules
are involved in collusion first step
collisions that's what it means if one
molecule decomposes you know molecular
to by molecular three molecules actually
term molecular right reactions so we
will have this kind of reactions in the
mechanism steps actually the mechanism
series of reaction between reactants and
the products as we describe that now
this is the explanation again that
termolecular that means collisions of
three molecules steps required three
molecules simultaneously collide with
the proper orientation and the proper
energy these are rare if they indeed do
a cure these must be slower than you
know molecular biomolecular step nearly
all mechanisms use only in a molecular
or by molecular reactions what does that
means that means that termolecular
reactions are too slow to be considered
usually right too slow to be considered
okay I guess this is the end of first
hour let's have a break and come back
after 15 No ten minutes right ten
minutes