Vapour Pressure of Solutions of Solids in Liquids Video Lecture | Chemistry Class 12 - NEET

hello friends this video on solutions
part 18 is brought to you by exam here
calm no more fear from exam fractional
distillation is on the important
application of God's law nor do we have
seen that you can easily find the
concentration of components in the vapor
phase so sometimes we have solution with
impurity and which is non-volatile
impurity so when you heat this here you
will get more substance more pure pure
substance why because in the vapor phase
in the vapor phase the partial pressure
could be the volatile compound will be
more because they are volatile right and
thus the mole fraction in the vapor
phase for the volatile compound to be
more correct see this has that suppose
more impurity the vapor phase will have
more components a more volatile and thus
you can then purify so this role flies a
huge application in fractional
distillation process let's talk about
the vapor pressure of solid in liquid
solution so I have solids in liquid so
good example of these solution you take
sodium chloride that is common salt you
take glucose urea you put this in water
or you take iodine to take Sulphur
dissolve then carbon die sulphide give
the examples of solutions where you
dissolve solid and liquid my solid is my
solute only it is my son so the reason
why you are studying this is VM it is
observed that physical properties of
these solutions these solutions are
different different from what
different from P or solid if you take
pure water you find the physical
property you think water mixed with
sodium chloride or glucose it will have
different physical property and this
physical property in talking borders for
example vapor pressure beautifully here
is different with a creature of a
solution which has solid solvent is
different from vapor pressure of a pure
solvent vapor pressure of sodium
chlorite water solution is different
from pressure of pure what they what is
evaporation so maybe pollution is the
pressure exerted by vapors of liquids
over the liquid phase and the liquid
condition so I will show you this is my
equilibrium condition here right all
this particles are moving around so the
vapors here here on this vapor phase
they exert a pressure over this liquid
phase is Malik witness the exert the
pressure over this liquid is under the
illyrian condition this is called
mutilation correct so you see in the
pure liquid form assuming this all
equilibrium condition
Eirene so the animation but just
understand that they are in equilibrium
condition they are moving around the
pure liquid solution if you see the
entire surface is occupied by the
molecules of the liquid correct if a
non-volatile solute is added to this
solution to the solvent you get a
solution this becomes a solution norm
right so in this you have non-volatile
solute then what happened the vapor
pressure the solution will have only
solvent but it will be less you see here
we have six molecules here we have three
we will discuss why the vapor pressure
has decreased now if you add a volatile
solid the assume this solid the big red
ones are volatile then you see some of
the volatile solutes also on the vapor
phase
correct and these all happens at a given
temperature at assuming that my
temperature is fixed and then also in
all this correct
so surface if you see of these all three
so if you talk about the pure solvent it
has only pure component we talk about
the solution the surface will have both
red and blue content right surface of
these has both solid and solvent
molecules that would happen is the
fractional surface area covered by
solvent is reduced so if you see here
since the red one is normal dyed it it
won't go up
but if you see here the more space I
mean it was easy for the blue particles
to come out but in this case if you see
the surface is occupied by the red
particles also there is survival of the
fittest snan your hair the blue particle
will not be able to come out without the
red particle is hogging the space heroes
if you see the red particle is now in
the space the blue party has won't be
able to come on thus since the blue
particle will not be able to come out
properly only few of the blue particles
will come to the vapor phase and then
the vapor pressure will decrease because
the vapor pressure is nothing but the
pressure exerted by the molecules here
right the liquid in this vapor phase but
if the vapors here is less the vapor
pressure will be less so if you see here
the six molecules may be exerting six
pressure here we need three three
pressure right here it is 4 so the vapor
pressure will definitely get reduced in
a given solution as compared to solvent
so in solvent if the pressure is that
suppose are 10 Pascal it will become
here 6 Pascal here it will become maybe
5 Pascal you don't know or say in Pascal
but both the cases both this pressure
will be lesser than the pure solvent
right also know that the decrease in the
vapor pressure which with this study in
detail the decrease in vapor pressure it
will depend
the quantity of non-volatile solute this
irrespective of its nature that means
whether you add sodium chloride or
potassium chloride - um iodide or
benzene doesn't matter it depends only
on the quantity it depends on the
quantity of non-volatile solute a
decrease in wave the pressure depends
only on the quantity of non-volatile
solid respective of it nature but it
doesn't depend on nature does not depend
on nature of sorry okay thus if you see
the decrease in vapor pressure by adding
1 mole of sugar - 1 kg water is almost
same that is produced by adding one mole
of urea to one liter of water so if you
take two example you take both to last
both has less about one liter water a
class 1 and class 2 in class 1 you add
let's suppose one mole of sodium
chloride in this case you add one mole
of urea both one mole why because one
mole is what one more is nothing but six
point zero 2 3 into 10 to power 23
molecules and here talking about the
quantity of molecules correct in the
most so you add one more of urea you are
below NSEL you add one more of potassium
iodide the decrease in vapor pressure
will almost be seen at a given
temperature right please don't we are
adding one more we are not saying I am
adding 1 gram of NaCl among refugia
because the moment you talk about the
gram you're not talking about the number
of molecules because here we had
concerned about number of molecules and
the number of molecules the best way to
represent is the number of moles because
1 mole is nothing but 6.0 - 3 to the 4
23 molecules correct
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