Copper Sulphate and Graphite Copper Electrodes

Copper Sulphate and Graphite Copper Electrodes


Let’s see how copper sulfate
undergoes electrolysis. And we’ll also try to see how
the nature of electrodes plays a very important role in the formation of the products. So
let’s start by using inert electrodes. So we carry out the electrolysis
of copper sulfate solution. And we use platinum or graphite electrodes.
Both are inert electrodes. That is, they do not participate in the
reaction So now, we have copper sulfate. It dissociates to
give copper ions and the sulfate ions. Water
dissociates to give H+ and OH-. So there are two cations and two anions in the solution. So let’s start with the cations first. So we have
Cu2+ and H+. So let’s look at the
electrode reactions for the cations and the anions. So we have the two cations, that this Cu2+ and H+ We know only one cation can
be discharged at the cathode. So we look for their
relative position in the electrochemical series. We see that the copper ion lies below hydrogen ions in the electrochemical
series. So copper ions, they get discharged at the cathode. So copper ion are discharged at the
cathode. So what is the reaction taking place at cathode? We have copper ion. Since they are
getting discharged at cathode, they take two electrons and
they form the neutral copper metal. The neutral copper metal is reddish-brown
in color and this is the product being formed at the cathode. Now let’s look at the anions. We have two anions in the solution. That is
sulfate and hydroxide. We know that only
one particular anion can be discharged at the anode. So for that, we look
for their relative position in the electrochemical series. so we see, that since hydroxide ions lie below the sulfate ions in the
electrochemical series, so OH- gets discharged at the anode. So now, OH- or hydroxide ions, they get discharged at the anode. So let’s
look at the reaction taking place at anode. So now, OH- in order to become
stable, it loses one electron, it forms OH. This OH species is not stable. So it
reacts with another OH to form water molecule and an oxygen atom. Now again the oxygen
atom on its own is not stable. It combines with another
oxygen atom to form oxygen gas. So the product being formed at the anode, is oxygen gas. So now, let’s look at the
electrolysis of copper sulfate solution. So in the beaker, we have taken by copper
sulfate solution which is blue in color. and we take
platinum or graphite electrodes, both of which are inert
electrodes. So let’s see how the electrolysis of copper sulfate takes place. So we see bubble formation taking place at one of the electrodes,
which is the anode as oxygen gas is being formed at the anode. And this reddish brown deposition on
cathode shows that copper metal is discharged
at the cathode as we had seen from the electrode reactions. So these are the products formed as a
result of electrolysis of copper sulfate solution
using inert electrodes. Now let’ carry out the electrolysis of
copper sulfate using activate electrodes. So this time, we use copper electrodes. Copper in this case, acts as an active
electrode. It wants to take part in the reaction.
that is, active electrodes, always participate in the electrolytic
reaction. Let’s see how that happens. So this time, we carry out the electrolysis
of copper sulfate solution using copper
electrodes. So let’s see what happens. We’re using copper anode and copper cathode. So they are separated by a mall
slip. We see that the bulb glows. This is
because the electrolysis is taking place. after sometime, it is observed that the anode wears off and the cathode gets thickened. This can
be seen from these markings and the extra projections. So what is
happening in this? Let’s try to find out. Again, when we have copper sulfate
solution, we have four ions. The ions remains the same. The dissociation
of copper sulfate gives us copper and sulfate ions. The dissociation of
water gives us H+ ions and OH- ions. So now, let’s look at the electrode reactions at
cathode and anode again. So we start with cathode. At cathode, we have copper ions and hydrogen ions. We know only one of them
can be discharged at the cathode. So if you look at their positions in the
electrochemical series, we see that the copper ions should
be discharged at the cathode. So the copper ions are being discharged
at the cathode and the product being formed at cathode is the
neutral copper atom or the copper metal that is being
formed at the cathode. Now let’s look at the, the reaction
taking place at the anode. We have two anions. Sulfate and hydroxide. Again we know that only one particular
anion can be discharged at the anode. So out of these two, we know that hydroxide ions should be
discharged at the anode. But remember this time we’re using
copper electrodes and we know that copper is an active electrode. So it participates in the reaction. So
how it does that, is it does not let the hydroxide ions to
be discharged at the anode. Instead, the reaction that takes place at anode is,
copper anode, that is the neutral copper, it enters the
solution in form of copper ions. So the copper anode that we are
using the neutral copper, it loses two
electrons and the copper enters the electrolytic solution as
Cu2+. So when we use active electrodes, that
is copper electrodes in this case, the OH- ions which should have been
discharged at the anode, they do not get discharged. Instead copper, which acts as an active
electrode, it enters electrolytic solution in the
form of Cu2+ ions. So what happens is, the anode wears off. This is because we had seen
the reaction at anode. The copper continuously enters
the electrolytic solution in the form of the Cu2+. So as
more and more copper atom from the copper anode, they enter the
solution. And the copper anode wears off. And this
ion, which is now present in the electrolytic
solution, they keep on depositing at the cathode. So we see that the copper cathode gets thickened. So why do we observed these
changes during the electrolysis of copper
sulfate using active electrodes? Because copper anode, it participates
in the reaction. The copper atom continuously
enters the solution in the form of copper ions. So the copper anode wears off.
And the copper cathode, Because of the deposition of copper ions,
it becomes thicker and thicker. So, so the copper electrodes during the
electrolysis of aqueous copper sulfate solution,
whether they act as active electrodes or inert electrodes. we’ve seen that when we use copper
electrodes, during the electrolysis of copper
sulfate solution, copper electrodes act as active electrodes. This is because the copper anode, it continuously
participates in the reaction. The copper atoms, from the anode, they continuously enter the electrolytic
solution in the form of copper ions. And so the copper electrodes they act as active electrodes during
the electrolysis of aqueous copper sulfate solution. This process, that is the electrolysis of a solution using activity electrodes
can be used as one of a very important application of electrolysis in
the modern day. This very important application of
electrolysis, is for the electrolytic refining of
metals. How is electrolysis used for the refining
of metals? Let’s see. So we have to refine copper. We have
to purify impure copper. So what do we do? We take thin strips of copper as cathode and we use impure copper that we have to purify as the anode.
So now these are the two electrodes that we use. So observe what happens. We have the impure copper. So this rod, or this anode is made up of impure
copper that we have to purify. And as cathode, we use pure strip of
copper. So what happens when the electrolysis
takes place? Since copper acts as active electrodes,
the copper from this anode continuously enters the
solution and its, and it keeps on depositing on the copper
cathode. So all the copper from this
impure rod enters the solution, and its, and it is
deposited at the cathode. And all the impurity that is present
at the anode, it is settled at the bottom as sludge. So the sludge consists all the
impurities which are present. So by using this technique, that is, if
we have to purify impure copper, or if we have to
refine impure copper, we, we make copper anode, made from the impure sample that
we had, that is made the anode. And pure copper is made as cathode.
As electrolysis takes place, copper acts as active electrodes, so copper atoms continuously enters
the electrolytic solution. as copper ions. And all the impure copper is therefore converted to pure copper.
So electrolysis can be used for the electrolytic refining
of metals. So in this case, we saw that when
we are using, copper, impure copper, to purify it, or refine it, what the observed is that
the impure sample, the impure slabs of the copper that we used as anode,
it gets finished. This is because as the process of
electrolysis takes place, all the impure copper present at the anode, it continuously enters the solution.
So the impure slabs get finished and the pure copper rod, which was used as the cathode, it becomes
thicker and thicker. So by using electrolysis We can purify or refine metal. And
this is one very important application of
electrolysis in the present day. That is the electrolytic refining
of metals. Electrolysis can be used to refine or purify impure metals.

28 Comments

  1. Anyone having trouble with NaOH electrolysis can watch this video https://www.youtube.com/watch?v=1FDzt5VP50c

    DeltaStep if you responded to student's doubts (due to errors in your videos) with the same frequency as you respond to thank you comments; not just me, many students would consider subscribing to your channel.

  2. What a great way to learn about electrolysis – the young lady is beautifully captivating, and an excellent presenter of her topic.

    A couple of minor points – nitrate ion in the electrochemical discharge series should have a SUBSCRIPT 3 after the oxygen O, and ONE minus sign above it; at present the formula looks like a trivalent nitric oxide anion!

    – It would have been interesting to know what your electrolysis current and voltage were during the experiments; and what lengths of time your experiments were run – the copper anode presumable did not disintegrate within a few seconds.

  3. u say that anode takes electron from ions in electrolyte solution so why the copper electrode at anode release electrons to form positive ion .

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