Electrolytic cell & Faraday’s law of Electrolysis
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| Electrolytic cell & Faraday’s law of Electrolysis |
Contents
Electrolytic cell
Faradays law of electrolysis
Definition of Electrolysis
Faradays constant
Faradays First and second laws of electrolysis
Difference between Galvanic and Electrolytic cell
Electrolytic cell
By passing an electric current through the system, it
is possible to create a cell that actually operates on a chemical process. They
are known as electrolytic cells.
An electrolytic device that employs electrical energy
to induce a non-spontaneous redox reaction is known as an electrolytic cell.
Certain chemicals can be electrolyzed using electrolytic cells, which are
electrochemical cells. For instance, water can be electrolyzed to create
gaseous oxygen and gaseous hydrogen with the use of an electrolytic cell. To do
this, the non-spontaneous redox reaction's activation energy barrier is
overcome by leveraging the flow of electrons (into the reaction region).
In that they both need a salt bridge, have a cathode
and anode side, and have a steady flow of electrons from the anode to the
cathode, so, electrolytic cells are extremely similar to voltaic
(galvanic) cells. But the two cells also differ dramatically from one another.
The following are the three essential parts of
electrolytic cells:
i.Cathode
ii.Anode
iii.Electrolyte
The cathode and anode exchange electrons through a medium that is provided by the electrolyte. In electrolytic cells, molten sodium chloride and water with dissolved ions are two common electrolytes. An electrolyte, commonly an ionic chemical that has been dissolved or fused, is in contact with two metallic or electronic conductors (electrodes) that are held apart from one another. The electrodes become positively and negatively charged when connected to a source of direct electric current, respectively.
In the electrolyte, negative ions migrate to the
positive electrode (anode) and transfer one or more electrons to it, creating
new ions or neutral particles. In the same way, positive ions migrate to the
negative electrode (cathode) and combine with one or more electrons, losing some
or all of their charge and creating new, lower-charged ions or neutral atoms or
molecules.
The two procedures combine to produce a chemical
reaction in which the negative ions' electrons are transferred to the positive
ions . The electrolysis of sodium chloride (common salt), which results in the
formation of sodium metal and chlorine gas, is one example; the energy needed
to drive the reaction forward is provided by the electric current. The
manufacture of caustic soda and electrodeposition for metal plating or
refinement are two other frequent uses of electrolysis.
Examples include are Downs Cell and Nelson cell.
Using an electrolytic cell, as shown below, it is possible to electrolyze molten sodium chloride (NaCl).
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| Electrolytic cell |
Molten sodium chloride, which comprises dissociated Na+ cations and Cl- anions, is used to saturate inert electrodes. The cathode accumulates electrons and creates a negative charge when an electric current is introduced into the circuit. Now, the sodium cations are directed to the cathode, which is negatively charged. As a result, metallic sodium is created at the cathode. The chlorine atoms are brought to the positively charged cathode at the same time. As a result, chlorine gas (Cl2) is produced at the anode (with loss of 2 electrons, finishing the process). Below are the relevant chemical formulae and the general cell reaction.
Thus, metallic sodium and chlorine gas can be produced
by electrolyzing molten sodium chloride in an electrolytic cell.
The main use of electrolytic cells is to create oxygen
and hydrogen gas from water. The technique of creating a thin protective layer
of one metal on the surface of another metal, known as electroplating, is
another noteworthy use of electrolytic cells. They are also employed in the
process of removing aluminium from bauxite. It should be mentioned that
electrolytic cells are virtually usually used in the industrial manufacture of high-purity
aluminium, high-purity copper, and high-purity zinc.
Faraday's law of electrolysis
In 1833, Michael Faraday found that the amount of
product generated or absorbed at an electrode during electrolysis and the
amount of electrical charge Q that moves through the cell are always related in
a straightforward way. Law illustrates the quantitative link between the amount
of electrical charge or electricity passed and the substance collected at
electrodes.
The half-equation, as an illustration
Ag++e–→Ag
Above equation Informs us that 1 mol of e- must be
provided from the cathode in order for 1 mol of Ag+ to deposit at cathode as 1
mol of Ag.
Electrolysis
A chemical change is induced by electrolysis, which
involves passing an electric current through an electrolytic solution to
stimulate the passage of ions. A liquid that conducts electricity is known as
an electrolyte, or often a salt solution of metal. Electrolysis is the use of
electric current to trigger a chemical process that is not naturally occurring.
Faraday Constant (F)
We may multiply
the charge per mole of electrons by the Avogadro constant to get the charge per
electron since the negative charge on a single electron is known to be 1.6022
10-19 C. The Faraday Constant is this number, denoted by the letter
F,
F = 1.6022 × 10–19 C × 6.0221 ×
1023 mol–1 = 9.649 × 104 C mol–1
Faraday’s First Law of Electrolysis
It is stated that “The mass of a substance deposited
at any electrode is directly proportional to the amount of charge passed.”
Mathematically it can be written as
m ∝ Q (i)
Here:
“m” is the mass
of a substance (in grams) deposited or liberated at an electrode. “Q” is the amount
of charge (measured in coulombs) or it is the electricity passed during
electrolysis
By converting the sign of proportionality in equation
(i) it becomes as follows
m=ZQ
where Z is the
constant of proportionality. Measured in g/c stands for grams per coulomb.
Alternatively, it is known as the electrochemical equivalent. Z is the mass of
an object deposited at electrodes during electrolysis while passing one
coulomb of charge.
Faraday’s Second Law
It states that “the mass of a substance deposited at
any electrode on passing a certain amount of charge is directly proportional to
its chemical equivalent weight.” Or “when the same quantity of electricity is
passed through several electrolytes, the mass of the substances deposited are
proportional to their respective chemical equivalent or equivalent weight”.
Mathematically it can be represented as follows
w ∝ E
w = mass of the
substance
E = equivalent weight of the substance
Second law is also written as follows
w1/w2=E1/E2
The equivalent weight or chemical equivalent of a
substance is defined as ratio of its atomic weight and its valency.
Equivalent weight=Atomic weight/Valency
Difference between Galvanic and Electrolytic cell
| Difference between Galvanic and Electrolytic cell |
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