L11 : Nernst Equation - Electrochemistry, Chemistry, Class 12 Video Lecture

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let's understand Nernst equation see
till now we assume that all the species
in God in this reaction all the
electrolytes where one molar that's what
we have assumed in law but in real life
that is not true
you may take two molar when we take
three molar limiting in waters that may
not be true later example it's
considered a half reaction reduction
half reaction actually for example this
guy here the reaction will be M sum M
with n plus ions it an electron the
transferred becomes M become sorry plus
AK was here let's take three action and
it was not 1 molar it has some
concentration and this B reaction of
this side correct so the electrode
potential at any concentration method
with respect to standard hydrogen
electrode can be what I'm saying is for
this concentration the electrode
potential for this half cell for a of MN
plus 2 m this will be nothing but e
naught e naught means standard of M n
plus 2 m minus RT by NF Ln errant key
key for this reaction K is nothing but
is put k ln k k is something we know is
nothing but concentration of M which is
solid by concentration of M and plus
ions then something we know equilibrium
constant this is the equation which was
there
experimentally by this guy is a very
very critical equation so let's say that
electrode potential at any concentration
that is I can say at any concentration
and this is standard electron standard
electrode potential which we generally
measure using sh e Shannon hydrogen
electrode right so till now what we've
done is we have used s achieves we
assume that potential to be zero
actually it is not and then we have
found the standard electrode potential
of copper and then we have found the
standard electrode potential of zinc
also assuming that anything is 1 molar
but now in real life it can be any
concentration so this equation holds
true right where we say that standard
for the electrode potential at any
concentration is nothing burn electrode
potential standard minus RT by NF Ln K
right where R is a gas constant R is my
gas constant 8.314 Joule per Kelvin per
mole F is what my Faraday constant I
will explain you how it came by at a
constant that is nothing but nine six
four eight seven Coulomb per ammonia and
then my T is what T is my temperature in
Kelvin in Kelvin and what on and this is
my concentration right K is my P and n
is my number of electrons which is
getting exchanged and this number of
letters
so first let's apply this equation for
Danielson and then we'll try to write
this lets up lines for Daniel's along so
for Daniel cell we have a node here AC
this is cathode here by presentation is
my jink is my copper this is my shed and
2 plus and this is my Sigma 2 plus right
opposite assumption so we will talk
about at the cathode first and cathode
so cathode now I have reduction
potential from see too fast too so
reduction potential of Cu 2 plus 2
copper at any concentration is nothing
but e naught cathodic cathode this is my
kitchen he not that we have still know
via file 0.34 volt I think ya minus RT
by n how many electrons are getting
transferred here to right two electrons
to F by Ln K what is the value of K so
let's see this reaction here we have Cu
2 plus becoming ceiling
solid plus plus 2 it right
not having concentration of copper solid
and that is always 1 by concentration of
Cu 2 plus that is this that is my
cathode you will find a node and a node
what is the reaction my this reaction I
have for a node that is nothing but my
Jing is taking two electrons becoming
yet into plus correct
correct but you want right the reduction
reaction it is nothing but flip side
flip side is nothing but the reduction
reaction will be nothing but please note
I have tried the reduction reaction for
this reduction reaction is it n 2 plus
will take 2 electron with them
so both case I am writing induction
reaction for finding the value of K
right I am finding reduction reaction
that is something to note so here I have
engendered 2 plus 2 Zn my reduction
putting is nothing but e not injured n 2
plus 2 gel n that is something we know
minus RT by n is 2 here f ln of
concentration of zinc solid is 1 by
concentration of zinc ions right please
note it is a reduction reaction if we
had it an oxidation reaction then you
would have written Ln of JN 2 plus by Ln
of JN solid it is when solid solid
concentration is 1 but be a writing
reduction reaction both case so we have
got cathode and anode both the value so
cell potential if you want to find the e
cell is nothing but e cathode minus Eno
lets applied these values EK there is
nothing but this guy P of Cu 2 plus 2 cu
- ye of little plus 2 then correct what
is the value of this yi of Cu 2 plus 2
cu in this guy he not Cu 2 plus 2 cu
minus RT by 2 f ln 1 by c unit 2 plus
minus this value ye of jaden 2 plus
together this is G 1 this is equation 2
so from Equation 2 I can put the value
of Z + 2 + 2 general is nothing but V
naught of
- plus - Jayden - same value RT by 2m Ln
of one right channel - she saw this you
get nothing word this is nothing but e
of Cu 2 plus PI 2 cu - or he not - II
not of Gen 2 plus PI Jaden which we
already know the - minus RT by 2 F Ln
this is - there is - right so whole
thing is - actually - well makeup glass
it comes up so this becomes 2 + by C and
this is nothing but if you see this
whole thing is nothing but standard ezel
he not self-correct so this becomes e
cell becomes e naught cell minus R T by
2 f ln of gels 2 + by C tables this is
only 1 than yourself right so let me
write this so final equation we got here
is yourself is nothing but e naught cell
because this is e naught 7 minus RT by 2
f ln o hidden - plus - that is my Nernst
equation and it gives a very good
picture it sees that electrode potential
or email per cell at any concentration
is nothing but email per se at 7
predation minus RT by ln zinc
concentration and copper concentration
that means the electrode or here or cell
at any concentration or isa electrode
potential of a cell at any concentration
but depending on the jincan copper
concentration if that is 1 1 both are 1
then 1 becomes 0 this is not there that
means the e cell at that point becomes
the standard electrode potential of the
cell
if the value is different right if you
increase the concentration of zinc the e
cell will decrease why because if you
increase the concentration of zinc the
whole value will increase and there is a
negative side here if you increase the
concentration of copper this whole value
will decrease in there is negative sign
negative positive that means e cell will
increase correct so that is my Nernst
equation for Daniel cells very very
important equation because it helps you
determine the electrode potential of a
cell at any concentration talk about any
concentration this is constant this we
know experimentation at 298 Kelvin using
assessee you can find this but this Yi
cell will vary based on the
concentration of electrolytes thank you
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