L12 : Solubility: Gas in Liquid, Henry law- Solutions, Chemistry, Class 12 Video Lecture

hello friends this video on solutions
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no more fear from exam now we talk about
solubility of gas in liquid right
for example here we'll talk about
example this is a gas and it dissolves
in liquid the best example of solubility
of gas and liquid is oxygen oxygen in
water see this oxygen dissolves in water
slightly even slightly but it has a huge
role for example all this aquatic
animals fish aquatic plants they need
this oxygen in fact all this aquatic
animals need is oxygen I predict plants
produce oxygen so even it is slightly
soluble but oxygen has a critical role
in water a seal gas this is highly
soluble in water
this is highly soluble in a word and now
this is highly impacted by pressure and
temperature why because the moment you
change the pressure the gas will have
impact change in temperature both liquid
and gas will have a pack so it is highly
impacted by pressure and temperature
change this oxygen gas I told this when
dissolved water it sustains all at many
life right so have you want what is the
source of the toxin the source of this
oxygen water is this aquatic inverse
plus oxygen here in the air so oxygen in
the air will be in equilibrium with
oxygen in water so they will keep moving
around it's oxygen in the air is also
source of oxygen in water oh I am making
my point clear see the source of oxygen
water is oxygen in air and oxygen from
this aquatic plants
as I have told the solubility of a gas
in liquid has a huge effect of pressure
so the effect is if you increase the
pressure the solubility of the gas in
solubility of gas in liquid increase
with increasing pressure the best
example as I told you the soda when the
soda bottle is packed the soda is liquid
it is packed at high pressure and then
when it is bad carbon dioxide is
dissolved in this since it is packed in
high pressure the carbon dioxide is
inside this nothing happens but the
moment you open the lid the high
pressure becomes low pressure because
now the pressure will be atmospheric
pressure if you have open bottle here
you have some liquid what is the
pressure here the pressure here will be
done at North intubation correct okay I
hope you know this why because you are
open to the atmosphere this pressure
here will be the atmospheric pressure
you must have known in physics moment
you open this it becomes atmospheric
pressure the pressure reduce the
pressure reduced solubility of gas
decrease is in the solubility of gases
decrease all this carbon dioxide comes
out as often and that is the reason why
when you have you have this coke bottle
you open it you see carbon dioxide
bubbles correct so we explained the
pressure effect of solubility of gas
liquid Henry proposed a law and this law
is called Henry law so proposed by him
bring in now 1803 it is the three this
way Henry proposed this law the law says
that the solubility of gas so a liquid
of gas in liquid this directly
proportional to the pressure of gas
pressure of gas of pressure above it
correct if my C is my solubility to be
directly proportional to the pressure of
yes he is mine solubility correct to
explain this body has told that for
example this beaker and there is some
gas molecule let's assume that this red
one is my carbon dioxide carbon like a
gas and this is my water solubility of
carbon dioxide in water it's
understanding now if you put this down
and the moment you put this down you
increase the pressure and now it do you
increase the pressure we see more and
more molecules of carbon dioxide Quadra
Zordon what we do you increase the
pressure you see more and more carbon
dioxide cortisol in water you increase
the pressure more and more carbon
dioxide got dis on what same thing
happens when they actually pack this
Cola bottle they pack it at high
pressure back and high pressure and then
that time more and more carbon dioxide
gets dissolved with this the moment you
open this the pressure is changing
becomes a constant pressure the carbon
dies and resolved and this is not able
to the solvent hair is not able to hold
the carbon dioxide and the carbon exit
comes out okay and that is the henry's
law actually so since he told solubility
is directly proportional to the pressure
right so he gave a constant called C is
equal to K into P gas so now I mean
there are so many laws actually for this
so many equations have the equation so
one says C is going to pay
yeah because viability is going to pay
into pressure gas other says pressure
gas is equal to solubility in some
constant so don't be confused with the
different variants of Henry law the unit
of K will actually tell you which
equation you have to follow right
example in this case if my pressure gas
is in ATM let's suppose here it is 80 mm
right and if this is solubility of a gas
it is let's suppose in moles per liter
then unit of this will be what moles
this will be moles per liter per atom
correctly moles per liter all right all
right Pacific correct yeah so this is
case the Henry's law constant so it's
pretty easy Lord saying that the moment
you increase the pressure solubility of
gas and liquid increase you talk about
Hindi you talk about Coca Cola don't
wait to talk about any hole or any Surat
ring then you think why how the moment
you open it you see carbon dioxide with
that reverse meaning you can say that
okay this Cola or this surah drain has
been panned at a high pressure the
moment you increase the pressure the
solubility increase decrease the
pressure solubility of a gas in liquid
decrease so let's recap the Henry
Lawrence real critical law solubility of
gas a liquid is directly proportional to
pressure correct some more things you'll
note about the Henry Louis it works only
in case of equilibrium because we talked
about solubility you talk about
equilibrium
hey only when it is in equilibrium we
talk about Henry law so it does involve
four gases at high pressure very high
pressure very high pressure you need
high pressure it does not work right it
doesn't work if chemical reaction take
place because if chemical reaction
reaction take place it does not work
because in a chemical reaction take
place then the new compound that is form
may be different it may occupy different
volume it may create extra pressure you
don't know so when the chemical reaction
take place for example carbon dies in
water this may not bother okay the good
example if you see carbon dies in water
use pure water and carbon dioxide so
carbon dioxide will react with pure
water to form h2 co3 so you Hindi now
may not work here okay also Henry law is
applicable only to dilute solutions only
to new solutions so more concentrated
the solution becomes more is the
deviation from ideal behavior we'll talk
about the ideal behavior nam right so
typically for mole fraction less than
point zero three henry lock work
perfectly fine and also this KH Kellie
we should be told right the the henry
constant is K H is function of
temperature because all these things
should happen in a given temperature so
with the KH value for a given compound
which Henry is proposed around for a
good number of solvent that is
impression dependent there are so many
things in the Hadid alright first thing
it happens to the equilibrium i happened
it doesn't high pressure it does not
work with chemical reaction take place
it works gently with the dilute
solutions and the KH value which we have
specified function of temperature this
is something which I want to tell you
because in the neuticals you will see
when the KH values vary the temperature
will also be measure let's write the
equation form in relock so as I told
solubility is directly proportional to
the pressure of the gas that is what
INRI has proposed so either you can say
that pressure of gas is equal to some
constant into C right or you can say
that solubility is some KH into TF both
this kind of solutions are when
equations are they in the market but
this is more prominent mostly used and
these two both K H are different not in
the this right now the unit of the K H
will determine which equation you have
to use right
so generally this is the equation that
is used most already now see the
solubility now we know that solubility
is what moles per liter I mean how many
solutes are dissolved in a particular
solvent right so it is the solubility we
can also use mole fraction mole fraction
can also be used we use to represent
solubility so in that case the equation
will become
pressure of gas is nothing but K H into
X X is nothing but more traction so in
this case if you see again the unit of K
H will change because SI was moles per
liter in this is unitless x is unitless
so unit of K H will change so this K H
is what th is my Henry's constant X is
the mole fraction and PS they were the
partial pressure of gas and vapor phase
liquid idea our slip pressure gas in
vapor stage
they toured this is function of
temperature right independent nice is
the mode right this is a most prominent
used Henry equation and it's for the
experiment done the mole fraction of HCl
in cyclic since I seen is my solute
cyclohexyl is a solvent here and this is
the partial pressure is observed
increase in normal direction the partial
pressure increased and then they could
easily seen is a relation actually at
the more traction is directly
proportional to the partial pressure
Dalton also gave one lakh during the
same time right
he also the contemporary Herning Henry
he also concluded independently actually
that the solubility of gas of gas liquid
right is directly proportional to
partial pressure of gas nothing great
same thing are done by dadam what Henry
did they Rock City the same thing he
showed that solubility increased with
increasing partial pressure still the
value of some henry constant in water
for helium hydrogen nitrogen oxygen and
the argon carbon dioxide right forward
behind anything i could write a
different temperature example if you see
oxygen has two values at 293 the KH
value is different at 3:03 the cage
velocity they told KH value is the
function of temperatures we have to
measure temperature and this cage value
is you have to find the cage value for a
pair for example carbon dioxide and
water pair helium in water pair
hydrogen water pair so some of the handy
constant with water is given and if you
see the unit of the cage
it is K bar that means the equation I am
looking here is P ass is nothing but K H
into X Y because the pressure is anyway
in bar kilo violet suppose an X is
unitless
so this will be also kaiba so from this
equation i will to this unit only i
could say that this is the equation i am
looking for here correct so it is the
equal unit of K H which will determine
which equation use in nineteen percent
case will you save equation this
equation by in person of the case
equation but and you see this is
temperature dependent nitrogen itself on
293 Kelvin this is the value of K H or
303 Kelvin this is the value K so having
understood the solubility of gas and
liquid the pressure effect let's talk
about the solubility of gases liquid
temperature what is the effect of
temperature so let us talk about the
solubility of gas and liquid the effect
of temperature we have seen the effect
of pressure right it see the effect of
compression see to visualize this just
visualize a boiling water when you boil
your water what happens you see bubbles
right bubbles coming out what does this
mean the moment you boil the water the
solubility is decreasing right and thus
the ball comes out same thing
the Kogelo the moment you open the can
the pressure decrease bubbles comes out
the pressure decrease will decrease the
solubility
here also temperature increase
temperature increase is doing one is
decreasing the solubility of gas in
liquid correct temperature increases
decreasing please note this is little
tricky normally when you increase the
temperature if you talk about the
solubility of saw so solid and liquid
hey Yuri the temperature solubility
increase you dissolve more sugar in a
glass of water a glass of warm water
then this then in the cold water but in
this case so you don't put a solubility
of gas in liquids the increase of
temperature actually decrease the
solubility to visualize this just think
of a boiling water moment you think of
boiling water you see the air bubbles
coming out right
the a robust comes out why because the
solubility of gas in the liquid decrease
and because of this what is happening is
the boil water if you have tested a bird
the boil water will taste bland why why
test plan because the dissolved oxygen
skip out the world okay
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