the effect of catalyzed
on equilibrium constant now the
catalysed remember increases the rate of
reaction right now it increases the rate
of reaction forward and increases the
rate of reaction and reverse also so
what really happens that the catalyze do
not have any changes do not have any
effect on the equilibrium constant and
equilibrium system but it only decreases
the time required to reach to the
equilibrium so if you have the catalyzed
actually and the time required to reach
the equilibrium will be shorter than the
same reaction without catalyze so here
what it says catalyze increases rate of
both forward and reverse reaction
equilibrium is achieved faster but the
equilibrium composition remains
unaltered equilibrium what does that
mean that means that the pollutant
constant is not changing right it's not
changing and activation energy or is
lowered allowing equilibrium to be
established at lower temperatures as a
matter of fact and but again the
equilibrium constant do not change only
this is again important only the time
required to reach to the equilibrium is
shorter as a matter of fact okay this is
the
and of equilibrium chapter now the next
chapter is thermodynamics that we will
cover thermodynamics
now thermodynamics actually is very very
important because thermodynamic deals
with energy and again remember energy
almost is involved in any process in any
I would say chemical reactions or other
physical processes any physical
processes as I said you one time the
beginning of the semester the energy
actually makes the world go around that
simply means if there is no energy there
will be nothing so energy is very very
important now
the thermodynamic deals with the energy
we said it deals with the changes of the
energy from one form to the other forms
and the efficiency of the energy used in
a process and so on so very very
important particularly for the engineers
some of the engine and mechanical
engineers and all engineers I guess now
before we start thermodynamics we should
probably remember few things from
Chapter five I guess is with thermo
chemistry now what we simply have to
remember system so when we say system in
thermodynamics that means it is the part
of the universe that we focus our
attention it is called system right we
define that before now then we simply
define surrounding
so surrounding again is defined as the
part of the universe after we take out
our system so the system and surround
them simply makes the universe right so
we should remember that again when we
say surrounded means we take out the
system and the rest is surrounded now I
should probably put over here that
system plus surrounding equals two
universe right that's what the terms are
now again we have talked about some
thermodynamic functions in Chapter five
in and that was the first one was two
and heat this is simply represented by Q
it is heat and W again is work and E is
internal energy that means the total
energy content of a system is called the
internal energy whatever that in any
form of the energies internal energy and
the change in internal energy is also
given by Delta e internal energy then we
have the relationship between the
internal energy change of the system and
the heat and work involved and that was
remember is Delta e is equal to Q plus W
and again here we
we talked about the pressure-volume work
this is equals to minus P times Delta V
volume change but this equation is very
very important and it simply says that
the total energy of the universe is
constant that means never changes total
energy so the energy can go from one
form to the others or the energy may be
transferred from the system to the
surrounding or from surrounding to the
system but as long as the total energy
of the universe that will never changes
and this is the expression mathematical
expressions of what first law of
thermodynamics right this is the first
law of thermodynamics first law of
thermodynamics now as you can say or
guess actually says we say it first law
that means there must be second and
third law and yes there are second and
third law of thermodynamics which we
will cover in this chapter we will again
explain those two but we have simply
talked about this first law that is the
first law of thermodynamics expression
actually internal energy equals to the Q
plus we heat and the work involved now
in addition to that there we have also
described the enthalpy change of a
system and again the enthalpy change of
a system is simply defined as the heat
involved under constant pressure that
means if the process is taking place on
the constant pressure the heat involved
is directly equals to the enthalpy
change
of that system so enthalpy is another
energy function actually thermodynamic
function and remember it is designated
by capital H the enthalpy and the change
in enthalpy is designated by Delta H
Delta H and the Delta H is equals to
simply Q sub P that means that the
process is taking place under constant
pressure so constant pressure constant
pressure and that's it so if I have the
heat change for the process which is
taking place under constant pressure
that is also equal to the enthalpy
change of the process as a matter of
fact and that's equal to now there's
also we have also seen the relationship
between the enthalpy change and the
internal energy change of the system
remember again the mathematical equation
which gives the relation between the
enthalpy and the internal energy is this
H is equal to e plus P times V these are
also functions again pressure and volume
actually of the system and that is the
enthalpy and when we simply take the
Delta H and we have to take the Delta e
here this is Delta e and this is going
to be Delta PV like this now remember
again Delta e and plus Delta PV would be
equals to P times Delta V and then V
times Delta P let's say it will be P
times Delta V and plus V times delta T
now remember if the process is taking
place under constant pressure Delta P
that means the change in pressure is
zero
because it's constant so this is simply
equals to zero
under constant T when the pressure so
the equation actually will be again as
follow Delta H is equals to Delta e plus
P Delta V P Delta V now we can simply
replace this P Delta V by minus V
because the work pressure volume work is
defined as minus P Delta V and we can
write down Delta e is Delta e equals to
Delta e minus W that is the work
involved work involved now again
remember the sign of these when we have
the two positive means that the system
absorbed heat and the process is
endothermic and if Q is minus negative
means that the process is exothermic
energy is released from the system to
the surrounding energy is released from
the system to the surrounding now the
sign of work is also if the system does
the work it is - if the system if the
work is done on the system the work sign
of the work will be + right so just like
the sign of - there is also a sign of
work we should be clear in our mind
about those signs again when we have
positive work negative work positive Q
and negative 2 and so on now in other
things that we have talked about is the
state function this is important also
state functions now we simply say that
if the change in a function going from
the initial to the final state is
independent of the path followed that
function is called a state function but
if the change in the function depends on
the path we follow from initial to the
final or from one point initial to the
final state actually then it will be not
a state function now here again internal
energy and enthalpy are state functions
these are simply state functions now we
can also add here pressure volume these
are also state functions - you can add
pressure volume temperature these are
also state function changing those it
doesn't matter which way you go actually
but on the other side the heat and work
is not a state function because it
actually depends how we go from initial
to the final or which path we follow to
go from initial to the final state in a
process so the work involved will be
different and the Q involved will also
be different but some of the work and
the Q which is the first law actually
that will not change right so you can
simply say by looking at the first law
that if the Q decreases W will increase
and so on those are but the sum will
always be the same so we can simply say
that Q and W are not state functions are
not state functions say functions okay
now actually thermal chemical
thermodynamics is the area of chemistry
it says that deals with the energy
relationship any energies involved in
chemical processes that will be
with the chemical thermodynamics
chemical thermodynamics we call it the
matter of fact now another term that we
should probably make clear is the
kinetics and thermodynamics
thermodynamics now
genetics tells us how fast the reaction
will take place right it is about the
speed of the chemical reactions but the
thermodynamics does not say anything
about the kinetics of the reaction it is
not it never is interested in how fast
the reaction will take place
what is thermodynamic is interested
thermodynamic is interested in to what
degree in a chemical reaction the
reactions will be converted to the
product and what does that means that
means the chemical thermodynamics or
thermodynamics is actually about the
system at equilibrium right about the
system at equilibrium it doesn't really
thermodynamic is not interested in how
fast the reaction will take place but it
is interested interested in how far the
reaction will go that means how far the
reaction will go until it reaches to the
equilibrium it always talks about the
equilibrium now actually you may have
thermodynamically
a reaction spontaneous reaction as we
will say but the rate of the reaction if
the rate of the reaction is very very
slow we can look at the reaction like
it's not taking place but according to
thermodynamics if the equilibrium
constant is large then it will say that
the reaction will take place but it
doesn't say anything about the speed of
the reaction so kinetics and
thermodynamics are two different areas
and they
look at the problem from two
perspectives one from the speed the
other one is only the colibri room
system if he interested in the
equilibrium system so since this is the
speed I should say more and this is the
equilibrium how fast and how far the
reaction will go how far the reaction
will go is thermo dynamics how fast the
reaction will go is about the kinetics
question ok now let's see look at here
what happened all right
let's look at the first line it says the
first law of thermodynamics again we
have talked about that here from chapter
5 that is the expression the total
energy of the universe is constant
energy can however be converted from one
form to another or transferred from a
system to the surrounding or vice-versa
from the surrounding to the system again
as we said so we know what surrounding
and system is here those are very
important that you should simply have
notions of those now we talked about the
enthalpy and now there is entropy which
is a new term it's again a thermodynamic
term thermodynamic function the enthalpy
is the heat absorbed by the system
during a constant pressure process as we
have said over here that's equal to Q
sub P we call it entropy is measure of
randomness in a system now both play
role in determining whether the process
is spontaneous or non-spontaneous now
there is another term came out here
spontaneous and non spontaneous as we
will talk about that later
spontaneous simply means that if a
process is taking place by itself
without any outside interference any
outside simply assistant and that
process is called
spontaneous process it just takes place
by itself right now the entropy again we
have to think about this again measure
of randomness in this systina system and
deals with me again as we see number of
microstates how many different ways the
energy and the positions of the
particles in the system can be different
from those are the number of microstates
actually and it is involved in number of
microstates so more like you know
randomness what is the opposite word of
this Ren
this what is the opposite of 10k else
right so it's actually a measure of
chaos chaos and the greater the chaos
actually the larger the entropy of the
system or greater than randomness the
larger the entropy if the randomness is
simply low then the entropy of that
system is low again like consider this
auditorium students sitting in the
chairs that is as an entropy now and now
if you every student starts walking
around and that system will also have a
entropy
now in which case the randomness is
higher when all students are walking in
the room right and that means that the
entropy of the system with the students
walking around in a classroom is higher
compared to the entropy of that
classroom when the students are sitting
in their chairs so this is like the
concept of entropy let's see we will
talk about that more now spontaneous
this is again important spontaneous
process spontaneous process again it
says precedes without any outside
assistance for example the gas in a
vessel a will spontaneously a fuse into
the vessel B but it will not
spontaneously be returned to vessel a
what this simply says actually as follow
if I have a gas over here like this and
then this is empty vacuum and here I
have the stopcock suppose that I open
that stopcock what will happen everybody
guess is that actually the gas from this
side a side will a fuse into the B side
and then finally it will fill out the
hole
a and B side of the flat this process is
a spontaneous process you don't have to
be anything just open the stopcock
that's all is let the gas go and expand
and fill out the hole but the reverse of
this spontaneous process what is that
means
and assuming that all gases when the
stopcock is open you have a gas all over
here homogeneously distributed in this
container assuming that all of the gases
in one time will go into this part
nothing on that side that is not
spontaneous at all right or we can
simply explain that with others now just
drop in this bull pen and fall in that
bull pen is a spontaneous process right
but getting back to this bull pen up
here is not a spontaneous process it
doesn't takes place by yourself I mean
so this is a game similar to that now
here again it says simply drop in these
two eggs like this is a spontaneous
process dropping of that and they break
actually but reverse of this these eggs
will never come together back and
reconstitute themselves be an egg and go
up here that is not a spontaneous right
so the processes that are spontaneous in
one direction are non spontaneous in the
reverse direction as we said over here
now this Spontini T of a process is very
important from the chemists standpoint
why because in chemistry we deal with
chemical reactions what is the chemical
reactions we have reactants we mix the
reactants and we want to get to us right
now
if a chemical reaction is spontaneous
means that as soon as you simply mix the
reactant species the product will form
right so that means to know the
spontaneity of a chemical reaction is
very very important if we know that the
chemical reaction is not spontaneous
there's no use
to try to get that product and try to
carry out that chemical reactions right
we can actually carry out that reactions
by using energy definitely but without
an outside interference it will not take
place if the reaction is not spontaneous
so the spontaneous reaction is
particularly used in industry are very
very important very very important so
the question is can we guess which
reactions will be spontaneous and which
reactions will not be spontaneous by
using thermodynamic data and thermo that
get the knowledge of thermodynamics yes
we will talk about that actually and as
we will see for the spontaneity there
are two main factors one is the energy
involved in the in the process and the
second is entropy change involved in the
process now the energy try to make the
process spontaneous in the direction
which the process will be exothermic
that means the energy try to make the
shift in reaction in an exothermic
directions but the entropy may not so we
have actually an energy we can call that
under constant pressure as the enthalpy
change and the entropy change are the
two factors that will determine whether
the process will be spontaneous or
non-spontaneous and we will see that
later again in this chapter now here it
says we can simply change the
spontaneity of a process by changing the
temperature of the process temperature
and pressure can affect the spontaneity
here again an example of how the
temperature affects it says very simple
for example if you have an ice at
greater than zero degree centigrade
under one atmosphere pressure let's say
10 degrees
11 degrees and so on what will happen
the ice will nowt to liquid water right
and this process is spontaneous but what
about zero degrees centigrade
now if we decrease the temperature below
zero degree centigrade then mountain of
ice will not be spontaneous right will
not be sparking so this is how
temperature simply affects the
spontaneity of the process now another
term that we should simply know
reversible and irreversible processes
reversible versus irreversible now
remember we have talked about reversible
reaction in chemical kinetics and also
equilibrium we said that every chemical
reaction is reversible and all
reversible reaction will reach through
an equilibrium
now that reversible and this reversible
are not exactly the same now reversible
simply means that let's look at here if
a process is taking place in one
direction spontaneously if an
infinitesimal amount of change reverses
that process in the opposite direction
means that process is reversible process
right now what does that means that
let's read it here it says the system
changes so that the system and the
surrounding can be returned to original
state by exactly reversion the process
this maximizes work done by the system
on the surrounding
but this reversibility should be the
case when you have an infinite system of
change of pressure
or temperature or volume or something
else that's what reversible simply means
now irreversible process cannot be done
by exactly reversion the change to the
system or cannot have the process
exactly followed reverse also any
spontaneous process is irreversible all
right now here is that's what we come in
now
usually the system not usually I guess I
should probably say always when we say
reversible process in chemistry we mean
the process at equilibrium now when we
say the irreversible process that means
that the process is far away from the
equilibrium it's going to the
equilibrium so all in Reverse all
spontaneous processes are irreversible
drop in that or anything that taken
place by itself but the equilibrium
system in fact for example if you have
let's put if you have a liquid and it's
vapor pressure in a closed system in
equilibrium if you just change in the
temperature just a little bit delta T
amount then the process will go in the
opposite direction right for example the
increase the pressure just a little bit
more that means that more gas molecules
will go into the liquid state now on the
other side if you change the pressure
just a little bit decrease the pressure
then the reverse process will take place
so the equilibrium system the system at
equilibrium can go to the right or to
the left by infinitesimal amount of
changes made in the factors and that is
the reversible process and otherwise
it's not reversible process so only
actually we just say that only the
system at equilibrium are considered as
reversible process as example mountain
of ice at zero degree centigrade is a
reversible process but mountain of ice
at 10 degree centigrade
is not a reversible process its
spontaneous process but not reversible
process and actually the below zero
degrees centigrade
again like freezing of liquid water
below zero degree centigrade is not
spontaneous
but freezing water at zero degree
centigrade is equilibrium and it's a
reversible process a reversible process
so that's what reversible simply means
in thermodynamics we should probably
keep that in mind
all right now entropy again let's think
about this a little bit more entropy can
be thought as a measure of randomness of
a system and it is a state function it
is a state function what does that means
just like internal energy and enthalpy
entropy which is designated by us is a
state function and the change in entropy
Delta s going from initial to the final
state will be independent of the path
that we follow and Delta s the end
entropy change is equal to the entropy
of the system in the final state minus
the entropy of the system at initial
State
now the entropy change can also be found
again as follow if we know the heat
involved in the process and also the
process is a reversible process then we
can calculate the entropy change for
that process if we know the temperature
and the temperature has to be constantly
temperature has to be constant now
what is that simply means let me just
explain for example
now for example when we have water solid
ice and that goes to gas water no okay
solid and liquid here let's make that
liquid and for this process Delta H
fusion cold fusion is given as 6.0 1
times 10 to the 3 joules per mole like
this now the entropy change let's say
this is 1 mole and this is also 1 more
like this and again at 1 atmosphere
pressure I can simply calculate the
entropy change melt in one mole of ice -
one mole of water and this is going to
be again as follow Delta s would be
equals to Delta H or I can say fusion
divided by the temperature but now let's
put that T over here and that will be
equal to Q reversible divided by under
constant pressure T over here and now I
can calculate this and that is going to
be six point zero one times 10 to the
three jewels term
and now tell me what is the temperature
what I should put the temperature there
yet yes Kevin but what value of
temperature 273 why yes so what
that simply means to have every versa
ball this is a reversible process right
to have that process reversible means
that it should be equilibrium case and
that equilibrium will be only at zero
degree centigrade which is 273 degree
centigrade yes that's what it is
otherwise if I put here another
temperature then this Delta s actually
will not be equal to that the entropy
change that we calculated it will not be
correct so we simply put here the
temperature which is 273 Kelvin in other
words it should be also Kelvin and then
we simply calculate that as here 20 2.0
joules per Kelvin per mole okay so now
what we have here the unit of entropy is
joules per Kelvin right joules per
Kelvin is the entropy unit and this is
per mole
every doesn't matter we can simply take
that but that is what the unit of
entropy joules per Kelvin like this but
you see again what I try to tell you
that reversible means in thermodynamics
that means the system is at equilibrium
equilibrium systems if this temperature
is at different temperature then the
mountain of ice it would be simply the
entropy will be different but it is not
going to be a reversible process
actually it's not going to be reversible
process
okay so let's continue here now the
second law of thermodynamics this is
again important the first law of
thermodynamics remember was the
conservation of energy yes I guess we
should stop here and let you go because