slide 1 of 31 chemistry 21.3. © copyright pearson prentice hall slide 2 of 31 electrolytic cells...

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Chemistry 21.3

© Copyright Pearson Prentice Hall

Slide 2 of 31

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 Cells >

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Electrolytic vs. Voltaic Cells


How do voltaic and electrolytic cells differ?

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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.

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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 Cells Electrolytic vs. Voltaic Cells21.3



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Electrolysis of Water

Electrolysis of Water

What products are formed by the electrolysis of water?

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>Electrolytic Cells Electrolysis of Water

The products of the electrolysis of water are hydrogen gas and oxygen gas.

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>Electrolytic Cells Electrolysis of Water21.3

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>Electrolytic Cells Electrolysis of Water

Balancing the Equation

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Electrolysis of Brine


What oxidation and reduction reactions occur during the electrolysis of brine?

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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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>Electrolytic Cells Electrolysis of Brine

Balancing the Equation

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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.

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Using Electrolysis in Metal Processing


How are electrolytic cells used in metal processing?

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Electrolytic cells are commonly used in the plating, purifying, and refining of metals.

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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.

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Animation 27

Take an atomic-level look at how electricity can bring about a chemical change.

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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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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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Section Quiz

-or-Continue to: Launch:

Assess students’ understanding of the concepts in Section

21.3 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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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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Concept Map 21

Solve the Concept Map with the help of an interactive guided tutorial.

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slide 1 of 31 chemistry 21.3. © copyright pearson prentice hall slide 2 of 31 electrolytic cells...

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