L25 : Kohlrausch Law: Numerical -2 - Electrochemistry, Chemistry, Class 12 Video Lecture

hello friends this video on electric
ministry part 25 is brought by exam
viacom known were clear from exam the
question says the conductivity of sodium
provided to 98 has been determined with
different concentration and the results
are given these are all conductivity of
NaCl so it's concentration of NaCl and
this is my 100 into K and okay Sukie
honey into k is connectivity so k will
be what this by 100 everything bad that
is what you live value of K you have to
find the lambda M for all concentration
plot between lambda and root C I need to
find the value of lambda
so let's find lambda M for all the
concentration in fine root C value and
then we can find the lambda I run from
the graph itself so let's see this the
same question here this is my NaCl
concentration the C value of C point
zero one is here point zero one is here
point zero two is here point zero five
here point zero point one here as I have
told here the conductivity is given a
hundred into this so I will just make
conductivity here so he will thing has
to be divided by 100 correct the same
barrows I have written here now lambda M
lambda gram is nothing but K by C what
is the value of K here K is in s per
meter C means per meter this is Siemens
per but I have to convert this into
Siemens centimeter square per mole so
what I will do I will divide this man
100 all right I will divide this KY
hundred to make it into Siemens per kilo
meter it admit it will be personal
correct and then see see what held is
moles per liter concentration is moles
per liter
I have to make it in moles per
centimeter view right this is an
see is in moles per liter I have to make
it moles per centimeter view so one
liter is nothing but 10 centimeter to
correct it should we try making
centimeter tube that means I have been
dividing into 10 cube that is somewhere
1000 will come here this will
accommodate say we solve this cancels
what you get is 10 K by C and the unit
will be what she means
this is centimeter per centimeter this
is centimeter cube centimeter cube into
percent limit this individual square and
it will be further more so dividend KY
see if you see that's what I wrote 10 K
by C so let's find well of 10 K bicycle
all 10 into K this value 1 point 2 3 7
into 10 to the power minus 2 by C that
is fine 0 and this value will come out
to be 1 23.7 let's find the value of 10
K by C here 10 into K is this value 11.8
524 miles see this fellow point 0 1 this
comes out to be 1 1 8.5 it's fine here
10 K is this value 23 point 1 5 10 to
the power minus 2 by C is point 0 2 this
comes out to be 1 1 5 point 8 simply 10
into K this value of fifty five point
five 3 10 to the power minus 2 by C is
point zero 5 it comes out to be 1 1 1
point 1 it's really here 10 into K this
value 106.7 4 10 to the power minus 2 by
C is point 1 it comes out to be
106.7 similarly you define root C
because it applaud the gravity root C
and lambda M right so C is given well
find would see root of point 0 0 1 that
is nothing but point 0 3 1 6 root of
point zero 1 is point 1 go to point 0 2
is point 1
one for 0.05 is 0.224 simple maths and
then root 0.1 is something one point
three one six let's plot the table at
point one concentration this is my point
one one generation the value is 0.3 one
the value is 106.7 so it will be
somewhere here 106.7 and we are here
only right actually and then we have to
plot for 0.5 points or five it is one
one one point zero five the
concentration will come out somewhere
here then I have point zero two
somewhere here at value is point one one
five somewhere here correct then I have
point one there is some hair and removal
will come out point eight here actually
and then I have point zero zero one very
less it will be 123 somewhere here right
so we see almost if you just join this
and this for strong electrolyte right
will just join this straight line in
Android properly just drawing it in the
straight line this will hit somewhere
here
124 this is hitting 124 here that means
my lambda M naught is 124 here it is
same that is C means centimeter square
but why because this is my malaria molar
conductivity at infinite dilution
correct pretty easy little bit math
involved but question is pretty
straightforward suggest a way to
determine lambda M naught for water sea
water is a very weak electrolyte if you
just keep water it won't is a sheet
it's a very weak electrolyte I want to
find the lamp I am NOT that means
infinite dilution what you not be able
to calculate using your normal physics
instrument we'd shown Greece right so
he'll give you the Kirchhoff's law
you'll say that lambda H 2o is nothing
but lambda for maybe H+ and OH H - if
you know this values the table right or
what you can do is water we can say
something like this you know the lambda
amount of HCl you can find the lambda M
naught of any or she can find lambda M
naught of NEC looking fine now if you
see if you add these two equation and
subtract this row including subtract any
and subtract you get HOH so I can say
that lambda naught of water is nothing
but lambda net of HCl plus NaOH minus
lambda naught of NEC that is also one
way of doing it
the next question is the molar
conductivity of point zero to five volt
per liter this is my concentration with
no gas it is given this is lambda M
calculates is degree of dissociation and
dissipation constant H so we'll have to
find K and we it also find the Alpha
correct we have been given that lambda
and of h plus and laminate of h co - is
given so the equation I have is a cos is
nothing but h co - plus h plus so I have
to find alpha so alpha is nothing but if
you see lambda m by lambda m not correct
lambda m is given lambda M naught if I
can find I can find alpha how can I find
lambda lambda M naught if I can find
using the Quadro slop
so if you see here lambda naught or
see us will be nothing but lambda not
off for a co - plus lambda out of a
space called ashram this is given five
point six Siemens per centimeter square
per mole please take care of this unit
and this is given three forty nine point
six Siemens per centimeter square or
more you add this to you get four zero
four point two seven centimeter square
per so what you have got you have got
the lambda non also lambda M is given
already we can find alpha okay so this
is given forty six point one seven
centimeter square per mole
it also please take care of unit this is
Amin centimeter square per mole so had
in the question if the units were
different here then the question would
have become complex but since the unit
is both same here which is little easy
so if you solve this you get point one
four K you can easily find for this
equation we know it come out to be C
alpha square by 1 minus L bar it easily
you can take C as a concentration
earlier this is zero this is zero at the
aquarium this becomes C into 1 minus
alpha this becomes C alpha becomes C
alpha so K is nothing but concentration
of a co Oh minus concentration of H+
divided by concentration of ICU H R is
nothing but C L Phi into CL v NC even
minus alpha will come out to be CL were
square 1 minus alpha what the value C is
nothing but point zero two five volt per
liter please note here I am taking moles
per liter only right I am NOT taking
mole per meter cube or centimeter cube
alpha I have 0.1 one four square and
this is one minus alpha is 0.14 so all
the values you get 3 point 6 7 into 10
to the power minus 4 moles per liter
because there is no unit for alpha that
is the value of K
last question of this more connectivity
easy question we have been given the
conductivity is this value conductivity
of a point to M solution that is this
the C is given to be this value we have
to find its molar conductivity
pdz lambda is K by C we know it what is
the value of K K is point zero two for a
Siemens per centimeter what is the value
of C C is point two moles per liter but
I want in centimeters one it resulting
but ten centimeter Square 1002 cube so
we solve this you get 120 for Siemens
centimeter square that is asked thank
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