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Chemistry 21.3
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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.
21.3
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Electrolytic Cells >
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Electrolytic vs. Voltaic Cells
Electrolytic vs. Voltaic Cells
How do voltaic and electrolytic cells differ?
21.3
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>Electrolytic Cells 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.
21.3
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Electrolytic Cells >
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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.
21.3
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>Electrolytic Cells Electrolytic vs. Voltaic Cells21.3
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>Electrolytic Cells Electrolytic vs. Voltaic Cells21.3
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>Electrolytic Cells Electrolytic vs. Voltaic Cells21.3
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Electrolytic Cells >
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Electrolysis of Water
Electrolysis of Water
What products are formed by the electrolysis of water?
21.3
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>Electrolytic Cells Electrolysis of Water
The products of the electrolysis of water are hydrogen gas and oxygen gas.
21.3
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>Electrolytic Cells Electrolysis of Water21.3
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>Electrolytic Cells Electrolysis of Water
Balancing the Equation
21.3
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Electrolytic Cells >
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Electrolysis of Brine
Electrolysis of Brine
What oxidation and reduction reactions occur during the electrolysis of brine?
21.3
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Electrolytic Cells >
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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.
21.3
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>Electrolytic Cells Electrolysis of Brine
Balancing the Equation
21.3
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21.3 Electrolysis of BrineElectrolytic Cells >
Battery
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>Electrolytic Cells Electrolysis of Brine
To produce chlorine and sodium hydroxide in electrolytic cells, electricity is passed through brine, a sodium chloride solution.
21.3
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Electrolytic Cells >
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Using Electrolysis in Metal Processing
Using Electrolysis in Metal Processing
How are electrolytic cells used in metal processing?
21.3
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Electrolytic Cells >
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Using Electrolysis in Metal Processing
Electrolytic cells are commonly used in the plating, purifying, and refining of metals.
21.3
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>Electrolytic Cells21.3 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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>Electrolytic Cells Using Electrolysis in Metal Processing
The cathode is the object to be plated. The anode is the plating metal.
21.3
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Electrolytic Cells >
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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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>Electrolytic Cells 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.
21.3
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>Electrolytic Cells 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.
21.3
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Section Quiz
-or-Continue to: Launch:
Assess students’ understanding of the concepts in Section
21.3 Section Quiz.
21.3.
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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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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
21.3 Section Quiz.
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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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