Transcript Electrolytic Cells

Chemistry 21.3
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21.3
Electrolytic Cells
DVDs have made it possible to
store large amounts of data in
a very small space. A laser is
used to transfer data to the
master DVD. You will read
about electrochemical
processes that require (rather
than produce) electrical
energy.
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Electrolytic vs. Voltaic Cells
Electrolytic vs. Voltaic Cells
How do voltaic and electrolytic cells
differ?
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Electrolytic vs. Voltaic Cells
An electrolytic cell is an electrochemical cell
used to cause a chemical change through the
application of electrical energy.
The process in which electrical energy is used to
bring about such a chemical change is called
electrolysis.
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Electrolytic vs. Voltaic Cells
The key difference between voltaic and
electrolytic cells is that in a voltaic cell,
the flow of electrons is the result of a
spontaneous redox reaction, whereas in
an electrolytic cell, electrons are
pushed by an outside power source,
such as a battery.
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Electrolytic vs. Voltaic Cells
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Electrolytic vs. Voltaic Cells
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Electrolytic vs. Voltaic Cells
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Electrolysis of Water
Electrolysis of Water
What products are formed by the
electrolysis of water?
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Electrolysis of Water
The products of the electrolysis of water
are hydrogen gas and oxygen gas.
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Electrolysis of Water
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Electrolysis of Water
Balancing the Equation
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Electrolysis of Brine
Electrolysis of Brine
What oxidation and reduction reactions
occur during the electrolysis of brine?
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Electrolysis of Brine
During electrolysis of brine, chloride
ions are oxidized to produce chlorine
gas at the anode. Water is reduced to
produce hydrogen gas at the cathode.
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Electrolysis of Brine
Balancing the Equation
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Electrolysis of Brine
Battery
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Electrolysis of Brine
To produce chlorine and sodium hydroxide in
electrolytic cells, electricity is passed through
brine, a sodium chloride solution.
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Using Electrolysis in Metal Processing
Using Electrolysis in Metal Processing
How are electrolytic cells used in
metal processing?
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Using Electrolysis in Metal Processing
Electrolytic cells are commonly used
in the plating, purifying, and refining
of metals.
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Using Electrolysis in Metal Processing
Electroplating and Electroforming
• Electroplating is the deposition of a thin layer
of a metal on an object in an electrolytic cell.
• Electroforming is a process in which an object
is reproduced by making a metal mold of it at
the cathode of a cell.
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Using Electrolysis in Metal Processing
The cathode is the object to be plated. The
anode is the plating metal.
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Using Electrolysis in Metal Processing
Animation 27
Take an atomic-level look at how electricity
can bring about a chemical change.
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Using Electrolysis in Metal Processing
Electrowinning
In electrowinning, impure metals are purified in
an electrolytic cell. Aluminum is produced from
alumina at the cathode of an electrowinning cell.
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Using Electrolysis in Metal Processing
Electrorefining
In the process electrorefining, a piece of impure
metal is made the anode of the cell. It is oxidized
to the cation and then reduced to the pure metal
at the cathode.
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21.3 Section Quiz.
Assess students’ understanding
of the concepts in Section 21.3.
Continue to:
-or-
Launch:
Section Quiz
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21.3 Section Quiz.
1. In electrolysis, an electric current is used to
a. cause a chemical change.
b. produce a battery.
c. generate heat.
d. run a motor
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21.3 Section Quiz.
2. During the electrolysis of water, the region
around the anode
a. changes color.
b. turns basic.
c. turns acidic.
d. remains neutral.
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21.3 Section Quiz.
3. Choose the correct words for the spaces. In
the net reaction for the electrolysis of water,
__________ is/are produced at the cathode
and ___________ is/are produced at the
anode.
a. hydrogen, oxygen
b. oxygen, hydrogen
c. hydrogen ions, hydroxide ions
d. hydroxide ions, hydrogen ions
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21.3 Section Quiz.
4. In the process of electroplating, the metal is
deposited by
a. reduction at the anode.
b. reduction at the cathode.
c. oxidation at the anode.
d. oxidation at the cathode.
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21.3 Section Quiz.
5. Which of the following processes does NOT
use the principles behind an electrolytic cell?
a. electroforming
b. electrowinning
c. electrorefining
d. electrochemical energy production
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Electrolytic Cells
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Concept Map 21
Solve the Concept Map with the help of an
interactive guided tutorial.
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