L4 : Daniell Cell - Electrochemistry, Chemistry, Class 12 Video Lecture

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exam so let's understand this danielson
this daniel cell again has zinc and
copper as electrodes you see there are
two electrodes zinc understand the color
of the xing looks like almost like
silver the copper you must have seen
copper Niehaus the reaction in this is
zinc plus copper sulfate gives zinc
sulphate in copper that is the whole
reaction then he'll sell see we see
chink has more reactor than carbon we
have seen just now so Jing becomes gel n
2 plus copper is reduced to copper plus
is reduced to copper right so here again
will first an order we have this anode
cathode issue so we first write a node
an ox and red guy the mobility we have
right so anode is where oxidation will
take place and reduction is where a
reduction think present cap you'll see
where it happens right so you see what
is the oxidation reaction so if you see
Jane to general plus 2 is what oxidation
reaction correct that is nothing but
anode and copper plus 2 copper is a
reduction reaction that will happen and
Kat correct this thing we know so we
have something called Anand we have
something Kolkata now the way it works
is this was designed by John Daniel John
Daniel John Daniel in 1836 it was the
British chemist actually and the main
thing was trying to do is he was trying
to remove that hydration global problem
hydrogen buffer problem so that in the
voltaic cell because voltaic pile
athletes in the voltaic pile also used
to generate electricity but that had
hydrogen problem she was trying to
eliminate that and the
potential for this is one point one volt
you'll see that and please note all the
concentration is 1 molar 1 mole this is
zinc sulphate 1 more this coppers of it
so what is done here is 1 mole of copper
sulfate this is sorry the blue one is
dipped in copper rod or here we have a
Jing krod dipped in 1 mole of zinc
self-correct
so I have this is my pink rod and this
is my copper as I told dink rod zinc
gets oxidized so it has to be announced
this has to be a known
similarly copper sulfate is reduced to
copper so this has to be a cathode okay
till responds clear so what we have done
is what John Daniel did is he took this
zinc in zinc sulphate copper and copper
solid please note zinc in zinc sulphide
copper and copper solid it easy right
this is zinc in zinc sulphate solution
copper and copper silver solution and
they're in two different beakers
separated by salt bridge I will tell you
why the salt bridge is used now what is
happening here is zinc we have in zinc
sulphate solution correct but the Jing
has a tendency to become dead in to plus
correct so jink from this if you see the
zinc metal is diminished why because the
jink
from this metal will try to become dead
in two plus by giving out two electron
correct and then gel n 2 plus will come
into this watch so I'll get two
electrons here right I am get two
electrons here in this metal these two
electrons will pass you see this is the
direction of electron flow I will come
back here so here will get
but two electrons through this wire and
that is what we are trying to achieve in
the electrochemistry right we are trying
to have this chemical reaction we are
trying to make the electron pass through
our external circuit and this electron
will produce electricity correct so the
same reaction we have seen that we have
a zinc dipped in a copper sulphate
solution where we yes all right the
reaction happens but they are also
electron transfer took place but the
electricity was not produced because the
electrons also has an internal so here
we are trying to do one thing we are
just separating this chemical reaction
trying to make sure trying to design
this electrochemical setup in such a way
that the electron is forced to transfer
in an external circuit so if you see him
zinc had tendency to become there n 2
plus so this chain here become 0 n 2
plus it gave 2 electron so electron was
somewhere here only
so electron was in this metal zinc metal
and got transferred through this wire
and it the bug view and now the electron
came back right since the electron came
back now this electron will be used by
copper sulphate solution this is the
copper sulfate right copper sulphate
solution this copper sulfate will take
this electrons to electrons and will
form copper right this copper sulfide
well so this copper plus will take this
2 electron see copper plus will take
this 2 electron will become copper so
reduction will happen here
zinc as I told jink will give become
redden +2 and give some 2 electrons
these 2 electrons transfer is surfing to
the circuit and this transfer of
electron will produce electricity and
please note the transfer of electron
transfer current is in the opposite
direction so the electron is
transferring in this direction the
current will transform correct and now
what happen what will happen is our
finsih T action happens if you see there
will be lot of gel and plus 2
right into the ground Regina plus 2 ions
in this correct and here it they'll have
lot of SFO one sense because the cuso4
if you see strong electrolyte it'll easy
bring into Cu plus two n is a book
device Cu plus two is being used but so4
2 one is still there correct
so that will produce have lot of s over
two miles lot of a solute levels and
this layer of gel n plus two miles will
be a difference in charge right and it
is not good so what will happen is we
need something to neutralize the charge
and for this we need something called
salt bridge to the salt bridge the salt
bridge here
there is nothing but it has some ions
and it is inverted tube right
so it is prepared by a filling agar agar
KCl agar agar KCl mixture it is a
u-shaped tube made of glass so jelly 3
agar agar solution resolved in 100 ml of
kcl solution and they don't react
chemically with the species example this
agar agar and PC solution will not react
with SFO to minus ion or well in plus
twoy they won't react right chemically
and this is just to maintain the lik
electrical neutrality in the solution
this is this has become a lot of
positive not not positive this solution
and this solution has become lot lot
negative negative solution this is a
positive solution to maintain the
neutrality what has happen is the salt
bridge through this salt bridge here we
have a support to - right it will flow
in this direction and here you have gel
plus - not on general plus - it flow in
this direction so you want see the
animation this is manual so you see the
electrons the green
my electrons here the electron is
flowing in this direction lot of SFO - -
here in this beaker right beacon which
is copper sulphate and lot of gel plus
2y on the left so to maintain the Newton
TVC to the salt bridge general +2 mine
is going in this direction and so2 - is
going in this direction in the salt
bridge and the electron is moving in
this direction so the current is going
in this direction right so electron
going left to right and they like
current going right to left so that is
the whole flow there you say so the the
main objective behind such a great
construction was to make sure the other
electron flows the electron which is
generated from this reaction if you have
example if you just keep this zinc and
copper sulphate ended in a container
this reaction will happen electron
transfer happens but this electron
transfer is not being utilized for a
useful purpose so the way it is the good
part here is this in this case is the
cell is constructed in such a manner
that this is used right the cell
transfer the electron transfer the
electrons is being used to generate
electricity
this electron for example here if you
see the electron came in this plate
because zinc became JN 2 plus and we got
2 electrons here right two electrons
here 2 electrons we got here why because
Ching became 2 plus and these 2
electrons now move in this direction so
once we have electrons here this
electrons here in the right hand side is
used by this copper sulphate solution
right so becomes copper and this copper
get the power it here but just some
photo minuses extra here this so4 2 -
here extra and this darrell plus 2 here
extra they create a charge difference
the salt bridge has to maintain the new
Trinity then in 2 plus goes in this
direction I support 2 minus cosine Z
direction the salt bridge is made in
such a way that the chemical inside this
is chemically inactive or inert - these
species so here I have KCl with agar
agar and this KCl is not reacted to in
general plus to our support o - correct
so if you talk about
this is my oxidation reaction the
reaction that happens at a node because
ox is my anode and this is my reduction
reaction it happens at Cal and this is
the whole reaction if you more this
reaction right you add these three
actually if you get this reaction you
see Jaden plus u two plus adding both on
the left-hand side you get this there in
plus two and cop on the right-hand side
you can plus two and cop on the
right-hand side two electrons two
electrons will get yes correct this is
my oxidation half-reaction reduction
half-reaction now have a total reaction
so I have three reactions here oxidation
half-reaction reduction half reaction I
mean when you add these two oxidation
half-reaction and reduction half
reaction you get an eighth reaction of
this please understand this danielson
because you understand the concept of
and danielson we can understand the
concepts of other cells which should be
discussing little improvement over the
daniell cell right Jing plus copper
sulphide solution reaction happens zinc
is more reactive imaging becomes n plus
2 and copper plus becomes copper this is
we know now the challenge was to make
this reaction happen in such a way that
the electron flows in the circuit so
that we can use this to generate
electricity and that what it is done
here Jing becomes n plus 2 because think
has tendency to becomes n plus 2 two
electrons are released here right this
electrons transfer perfect circuit you
get two electrons here these two
electrons are being used by na copper
plus this in the solution to create
copper and copper gets deposited so if
we see over a period of time you see
more and more copper here and less and
less zinc air and since here in this
jink if you see lot of lot of electrons
may there so see so we gave a negative
charge to this node see a negative
charge why because they will all lot of
electrons here it get accordingly charge
here we had deficiency of electrons in
use encode a positive charge please note
in chemistry we only talk about anode
and cathode
an oxidation take place cathode where
production take please positive and
negative charge you have to actually
calculate base on this reaction where
you are getting more electron density
that becomes negative charge where you
get electron deficit any other becomes
positive charge now let's see the
Daniell cell has electrolyte itself now
please note here is the Daniell cell
voltage told you is 1 point 1 volt right
now if you apply a potential opposite
potential here right if you apply a
pause opposite potential here what will
happen so things will change example if
you see electron will flow in this
direction because the potential have
applied here this is more than 1 point 1
volt this is let's suppose is 5 volt and
this seller 1 more 1 v 1 volt so net if
you see is this is the bigger or
stronger battery this is stronger
battery if it is 1 more than one point
one would because this whole thing is 1
point 1 volt this is 5 volt is modem
obviously 1 point 1 volt is a strong and
battery this will rule so it has
negative charge here so you have put it
here and you put this here right so in
this case what happen is the electron
will flow in this direction correct you
know it is a battery here
using positive or negative charge the
electron flows from negative to positive
and the current flows in the other way
direction its electron flows in this
direction current flows in this back
electron flows in this direction now at
this point when you have when you
provide a more voltage to this Daniell
cell it works as electrolyte except we
will discuss electro a pixel in more
details actually where we use this for a
non-spontaneous reaction here what will
happen in since it has got electrons
here so del n 2 plus in the solution
will become zinc if there is
there is Samia and here it has got more
deficit of electrons so here copper will
get oxidized to copper plus C we see
this is non-spontaneous reaction rate
generally typically Jing will not try to
become Jaden Jaden
the student is a non-spontaneous it will
not happen right
sim really see you - see you - plus his
non spontaneous if we compare copper and
zinc in the same solution because ink is
more reactive but this reaction will
happen if you apply external correct
there was a non spontaneous reaction it
will happen if you apply external so you
see this is now non spontaneous reaction
which is happening because of the
external electrical energy and that is
nothing but my electrode electrolyte
Excel correct thank you
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