Electrolysis

Electrolysis

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In chemistry, the production of chemical changes by passing an
electric current through a solution or molten salt (the electrolyte),
resulting in the migration of ions to the electrodes: positive ions
(cations) to the negative electrode (cathode) and negative ions
(anions) to the positive electrode (anode).

During electrolysis, the ions react with the electrode, either
receiving or giving up electrons. The resultant atoms may be liberated
as a gas, or deposited as a solid on the electrode, in amounts that
are proportional to the amount of current passed, as discovered by
English chemist Michael Faraday. For instance, when acidified water is
electrolysed, hydrogen ions (H+) at the cathode receive electrons to
form hydrogen gas; hydroxide ions (OH-) at the anode give up electrons
to form oxygen gas and water.

One application of electrolysis is electroplating, in which a solution
of a salt, such as silver nitrate (AgNO3), is used and the object to
be plated acts as the negative electrode, thus attracting silver ions
(Ag+). Electrolysis is used in many industrial processes, such as
coating metals for vehicles and ships, and refining bauxite into
aluminium; it also forms the basis of a number of electrochemical
analytical techniques, such as polarography.



Faraday's laws
==============

Three laws of electromagnetic induction, and two laws of electrolysis,
all proposed originally by English scientist Michael Faraday:

Induction (1) a changing magnetic field induces an electromagnetic
force

In a conductor; (2) the electromagnetic force is proportional to the
rate of change of the field; (3) the direction of the induced
electromagnetic force depends on the orientation of the field.

Electrolysis (1) the amount of chemical change during electrolysis is
proportional to the charge passing through the liquid; (2) the amount
of chemical change produced in a substance by a given amount of
electricity is proportional to the electrochemical equivalent of that
substance.



Faraday's constant
==================

Constant (symbol F) representing the electric charge carried on one
mole of electrons.

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Related Searches

It is found by multiplying Avocado's constant by
the charge carried on a single electron, and is equal to 9.648 x 104
coulombs per mole.

One faraday is this constant used as a unit. The constant is used to
calculate the

Electric charge needed to discharge a particular quantity of ions
during

Electrolysis.

Faraday, Michael (1791-1867)

English chemist and physicist. In 1821, he began experimenting with
electromagnetism, and discovered the induction of electric currents
and made the first dynamo, the first electric motor, and the first
transformer. Faraday isolated benzene from gas oils and produced the
basic laws of electrolysis in 1834.He also pointed out that the energy
of a magnet is in the field around it and not in the magnet itself,
extending this basic conception of field theory to electrical and
gravitational systems.

Chemistry and the discovery of benzene Faraday was mainly interested
in chemistry during his early years at the Royal Institution. He
investigated the effects of including precious metals in steel in
1818, producing high quality alloys that later stimulated the
production of special high-grade steels. In 1823, Faraday produced
liquid chlorine by heating crystals of chlorine hydrate in an inverted
U- tube, one limb of which was heated and the other placed in a
freezing mixture. After the production of liquid carbon dioxide in
1835, he used this coolant to liquefy other gases. In the same year,
Faraday isolated benzene from gas oils and demonstrated the use of
platinum as a catalyst. He also demonstrated the importance in
chemical reactions of surfaces and

Inhibitors, foreshadowing a huge area of the modern chemical industry.



Laws of electrolysis
====================

Faraday's laws of electrolysis established the link between
electricity and chemical affinity, one of the most fundamental
concepts in science. Electrolysis is the production of chemical
changes by passing an electric current through a solution. It

Was Faraday who coined the terms anode, cathode, cation, anion,
electrode, and electrolyte. He postulated that, during the
electrolysis of an aqueous electrolyte, positively- charged cations
move towards the negatively-charged cathode and

negatively-charged anions migrate to the positively charged anode.
Faraday demonstrated that the ions are discharged at each electrode
according to the following rules:

(a) The quantity of a substance produced is proportional to the amount
of electricity passed;

(b) The relative quantities of different substances produced by the
same amount of electricity are proportional to their equivalent
weights (that is, the relative atomic mass divided by the oxidation
state or valency).

Electromagnetism and the electric motor in 1821, only one year after
Hans Oersted had discovered with a compass needle that a current of
electricity flowing through a wire produces a magnetic field, Faraday
was asked to investigate the phenomenon of electromagnetism by the
editor of the Philosophical Magazine. Faraday conceived that circular
lines of magnetic force reproduced around the wire to explain the
orientation of Oersted's compass needle. Faraday's conviction that an
electric current gives rise to lines of magnetic force arose from his
idea that electricity was a form of vibration and not a moving fluid.
He believed that electricity was a state of varying strain in the
molecules of the wire conductor, and that this gave rise to a similar
strain in the medium surrounding the conductor. It was reasonable to
consider therefore that the transmitted strain might set up a similar
strain in the molecules of another nearby conductor.

Faraday set about devising an apparatus that would demonstrate the
conversion of electrical energy into motive force. His device
consisted of two vessels of mercury connected to a battery. Above the
vessels and connected to each other were

Suspended a magnet and a wire, which were free to move and dipped just
below the surface of the mercury. In the mercury were fixed a wire and
a magnet respectively. When the current was switched on, it flowed
through both the fixed and free wires,

generating a magnetic field in them. This caused the free magnet to
revolve around the fixed wire, and the free wire to revolve around the
fixed magnet.

The experiment demonstrated the basic principles governing the
electric motor. Although the practical motors that subsequently
developed had a very different form to Faraday's apparatus, he is
usually credited with the invention of the electric motor.

Electromagnetic induction and the transformer Faraday hunted for the
effect of

Electromagnetic induction from 1824 onwards, expecting to find that a
magnetic field would induce a steady electric current in a conductor.
Faraday eventually succeeded in producing induction in 1831. He wound
two coils around an iron bar and connected one to a battery and the
other to a galvanometer (an instrument for detecting small electric
currents by their magnetic effect). Nothing happened when the current
flowed through the first coil, but Faraday noticed that the
galvanometer responded whenever

the current was switched on or off. Faraday found an immediate
explanation with his lines of force. If the lines of force were cut -
that is, if the magnetic field changed - then an electric current
would be induced in a conductor placed within the magnetic

field. The iron bar helped to concentrate the magnetic field, as
Faraday later came to understand, and a current was induced in the
second coil by the magnetic field momentarily set up as current
entered or left the first coil. With this device, Faraday had
discovered the transformer, a modern transformer being no different in
essence even though the alternating current required had not then been
discovered.

Faraday is thus also credited with the simultaneous discovery of
electromagnetic induction, although Joseph Henry had made the same
discovery in the same way in 1830. However, busy teaching, Henry had
not been able to publish his findings before Faraday did, although
both men are now credited with the independent discovery of induction.

Arago's wheel and the electric generator in 1824, Francois Arago found
that a rotating non-magnetic disc, specifically of copper, caused the
deflection of a magnetic needle placed above it. This was in fact a
demonstration of electromagnetic induction, but nobody at that time
could explain `Arago's wheel´. Faraday realized that the motion of the
copper wheel relative to the magnet in Arago's experiment caused an
electric current to flow in the disc, which in turn set up a magnetic
field and deflected the magnet. He set about constructing a similar
device in which the current produced could be led off, and built the
first electric generator in 1831. It consisted of a copper disc that
was rotated between the poles of a magnet; Faraday touched wires to
the edge and centre of the disc and connected them to a galvanometer,
which registered a steady current.

Electrostatic charge In 1832 Faraday showed that an electrostatic
charge gives rise to the same effects as current electricity. He
demonstrated in 1837 that electrostatic force consists of a field of
curved lines of force, and that different substances have specific
inductive capacities - that is, they take up different amounts of
electric charge when subjected to an electric field.

In 1838, he proposed a theory of electricity elaborating his idea of
varying strain in molecules. In a good conductor, a rapid build-up and
breakdown of strain took place, transferring energy quickly from one
molecule to the next. This also accounted for the decomposition of
compounds in electrolysis. At the same time, Faraday wrongly rejected
the notion that electricity involved the movement of any kind of
electrical fluid (the motion of electrons is involved). However, in
that this motion causes a rapid transfer of electrical energy through
a conductor,

Faraday's ideas were valid.



Polarization of light
=====================

Finally, Faraday considered the nature of light and in 1846 arrived at
a form of the electromagnetic theory of light that was later developed
by Scottish physicist James Clerk Maxwell. In 1845, Lord Kelvin
suggested that Faraday investigate the action of electricity on
polarized light. Faraday had in fact already carried out such
experiments with no success, but this could have been because
electrical forces were not strong. Faraday now used an electromagnet
to give a strong magnetic field instead and found that it causes the
plane of polarization to rotate, the angle of rotation being
proportional to the strength of the magnetic field.



Paramagnetic and Diamagnetism
=============================

Several further discoveries resulted from this experiment. Faraday
realized that the glass block used to transmit the beam of light must
also transmit the magnetic field, and he noticed that the glass tended
to set itself at right-angles to the poles of the magnet rather than
lining up with it as an iron bar would. He showed that the differing
responses of substances to a magnetic field depended on the
distribution of the lines of force through them. He called materials
that are attracted to a magnetic field paramagnetic, and those that
are repulsed diamagnetic. Faraday then went on to point out that the
energy of a magnet is in the field around it and not in the magnet
itself, and he extended this basic conception of field theory to
electrical and gravitational systems.

Faraday was born in Newington, Surrey, and was apprenticed to a
bookbinder; he was largely self- educated. In 1812, he began
researches into electricity, and made his first electrical cell. He
became a laboratory assistant to Humphry Davy at the Royal Institution
in 1813, and in 1833 succeeded him as professor of chemistry. Faraday

delivered highly popular lectures at the Royal Institution 1825-62. He
refused to take part in the preparation of poison gas for use in the
Crimean War.

Aim: I shall conduct an experiment, which will see how much copper is
deposited during the electrolysis of copper sulphate. Copper Sulphate
is the electrolyte of this experiment. Electrodes are materials
connected to the negative terminal of the negative terminal of the
battery and is called Cathode the electrode connected to the positive
terminal of the battery is Anode. Many factors will effect this
experiment time, as there is a limited time to conduct this experiment
due to class period.

· Time

· Current

· Concentration Of Solution

· Temperature

· Distance Between Electrodes

· Quantity Of Solution

· Size Of Electrodes

Predictions: I think that if you put more current you should get more
copper deposited as the current passes quicker thought the circuit.
You can calculate how much copper will be deposited at the cathode by
using the following equation:

Q=I*T

Where Q=Amount of charge (electrons) in coulombs

I=Current in amps

T=Time in seconds

I think during electrolysis, copper ions are will be attracted towards
the positive anode. Copper atoms which make up the anode each will
give up two electrons to form CU2+ ions. The overall result I think
will be that the anode loses weight as the cathode gains weight.

Below are some of my predicted results which I complied from my
preliminary experiments.

Predicted Results

Voltage

Current

Time

Cathode before

Cathode after

Anode before

Anode after

Cathode difference

Anode difference

4.5

1.00

10min

1.5

1.16

1.8

1.6

0.11+

-0.2

4.5

1.23

20min

1.6

2.0

1.7

1.4

0.4+

-0.3

4.5

1.30

30min

1.9

2.1

1.4

1.1

0.2+

-0.3

4.5

1.70

35min

2.1

2.5

1.4

1.2

0.4+

-0.2

6

1.00

10min

1.9

2.0

1.7

1.6

0.1+

-0.1

6

1.11

20min

1.9

2.1

1.8

1.4

0.2+

-0.4

6

1.19

30min

1.9

2.3

1.9

1.4

0.5+

-0.5

6

0.83

35min

1.5

1.6

2.4

2.2

0.1+

-0.2

[IMAGE]

[IMAGE]

Equipment:

* Two Copper Electrodes[Anode(+)Cathode(-)]

* Beaker

* Voltmeter

* Ammeter

* Copper Sulphate Solution

* Battery Power Pack

* Splints

* Crocodile Clips

* Circuit Wires

Method: I first with my friend's we gathered all necessary equipment
for this experiment we got Two Copper Electrodes, A Beaker ,Voltmeter,
Ammeter, Copper Sulphate Solution, Battery Power Pack and some
Splints.

I set the equipment as shown in the diagram below. I got a beaker and
poured 500ml of Copper Sulphate Solution. The Copper Electrodes were
then placed into the solution and then were held against the beaker
with splints. I connected up the wires to the battery pack then to the
ammeter and to the electrodes at the wire that's going towards the
electrodes we added Crocodile Clips and then clipped it on to the
Copper Electrodes. We then used two different voltages 4.5 and 6 we
used the two different voltages with different times. They were 10min,
20min, 30min, 35 min we used these times on both the different
voltages. We stopped them at these times to record the difference in
weight at the beginning of the experiment. At this time we turned of
the current and weighted the Electrodes. We looked at the solution,
current, the weight of the copper electrodes; we looked at all of
these at the end of each experiment. During the experiment we noticed
that the current fluctuated and that there was the impure Copper left
at the bottom of the beaker as Sludge.

[IMAGE]

Voltage

Current

Time

Cathode Before

Cathode After

Anode After

Anode After

Cathode Difference

Anode Difference
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