chemistry 21.1
DESCRIPTION
Chemistry 21.1. Electrochemical Cells. 21.1. Fireflies, anglerfish, luminous shrimp, squid, jellyfish, and even bacteria give off energy in the form of light as a result of redox reactions. You will discover that the transfer of electrons in a redox reaction produces energy. 21.1. - PowerPoint PPT PresentationTRANSCRIPT
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Chemistry 21.1
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Electrochemical Cells
Fireflies, anglerfish, luminous shrimp, squid, jellyfish, and even bacteria give off energy in the form of light as a result of redox reactions. You will discover that the transfer of electrons in a redox reaction produces energy.
21.1
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>Electrochemical Cells Electrochemical Processes
Electrochemical Processes
For any two metals in an activity series, which metal is more readily oxidized?
What type of chemical reaction is involved in all electrochemical processes?
21.1
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Electrochemical Cells >
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Electrochemical Processes
For any two metals in an activity series, the more active metal is the more readily oxidized.
21.1
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>Electrochemical Cells Electrochemical Processes
A Spontaneous Redox Reaction
21.1
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>Electrochemical Cells Electrochemical Processes21.1
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>Electrochemical Cells Electrochemical Processes21.1
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>Electrochemical Cells Electrochemical Processes
Redox Reactions and Electrochemistry
All electrochemical processes involve redox reactions.
• An electrochemical process is any conversion between chemical energy and electrical energy.
• An electrochemical cell is any device that converts chemical energy into electrical energy or electrical energy into chemical energy.
21.1
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Electrochemical Cells >
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Voltaic Cells
Voltaic Cells
How does a voltaic cell produce electrical energy?
21.1
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>Electrochemical Cells Voltaic Cells
Electrical energy is produced in a voltaic cell by spontaneous redox reactions within the cell.
Voltaic cells (named after their inventor) are electrochemical cells used to convert chemical energy into electrical energy.
21.1
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>Electrochemical Cells Voltaic Cells
Constructing a Voltaic Cell
• A half-cell is one part of a voltaic cell in which either oxidation or reduction occurs.
• The half-cells are connected by a salt bridge—a tube containing a strong electrolyte, often potassium sulfate (K2SO4).
21.1
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>Electrochemical Cells Voltaic Cells
An electrode is a conductor in a circuit that carries electrons to or from a substance other than a metal.
• The electrode at which oxidation occurs is called the anode.
• The electrode at which reduction occurs is called the cathode.
21.1
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>Electrochemical Cells Voltaic Cells
Volta built his electrochemical cell using piles of silver and zinc plates separated by cardboard soaked in salt water. He used his cell to obtain an electrical current.
21.1
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>Electrochemical Cells Voltaic Cells
How a Voltaic Cell Works
21.1
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21.1 Voltaic Cells>Electrochemical Cells
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21.1 Voltaic Cells>Electrochemical Cells
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Voltaic Cells>Electrochemical Cells21.1
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Voltaic Cells>Electrochemical Cells21.1
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Voltaic Cells>Electrochemical Cells21.1
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>Electrochemical Cells Voltaic Cells
Representing Electrochemical Cells
You can represent the zinc-copper voltaic cell using the following shorthand.
21.1
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Electrochemical Cells >
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Using Voltaic Cells as Energy Sources
Using Voltaic Cells as Energy Sources
What current technologies use electrochemical processes to produce electrical energy?
21.1
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Electrochemical Cells >
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Using Voltaic Cells as Energy Sources
Current technologies that use electrochemical processes to produce electrical energy include dry cells, lead storage batteries, and fuel cells.
21.1
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>Electrochemical Cells Using Voltaic Cells as Energy Sources
Dry Cells
A dry cell is a voltaic cell in which the electrolyte is a paste. The half reactions for one type of dry cell are shown below.
21.1
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>Electrochemical Cells Using Voltaic Cells as Energy Sources
Both dry cells and alkaline batteries are single electrochemical cells that produce about 1.5 V.
21.1
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>Electrochemical Cells Using Voltaic Cells as Energy Sources
Lead Storage Batteries
A battery is a group of cells connected together. The half-reactions for a lead storage battery are as follows.
21.1
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>Electrochemical Cells Using Voltaic Cells as Energy Sources
A 12-V car battery consists of six voltaic cells connected together. One cell of a 12-V lead storage battery is illustrated here.
21.1
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>Electrochemical Cells Using Voltaic Cells as Energy Sources
21.1
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>Electrochemical Cells Using Voltaic Cells as Energy Sources
Fuel Cells
Fuel cells are voltaic cells in which a fuel substance undergoes oxidation and from which electrical energy is continuously obtained.
21.1
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>Electrochemical Cells Using Voltaic Cells as Energy Sources
The hydrogen-oxygen fuel cell is a clean source of power. Such cells are often used in spacecraft.
21.1
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Section Quiz
-or-Continue to: Launch:
Assess students’ understanding of the concepts in Section
21.1 Section Quiz.
21.1.
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21.1 Section Quiz.
1. Zn is above Pb in the activity series of metals. Which of the following statements is correct?
a. Zn will react with Pb2+.
b. Pb2+ will react with Zn2+.
c. Zn2+ will react with Pb.
d. Pb will react with Zn2+.
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21.1 Section Quiz.
2. The reactions that take place in electrochemical cells involve electron transfers. What name is given to such reactions?
a. oxidation reactions
b. reduction reactions
c. spontaneous redox reactions
d. double replacement reactions
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21.1 Section Quiz.
3. Portable sources of electrical energy consisting of groups of voltaic cells connected together are called
a. batteries
b. alkaline cells.
c. dry cells.
d. fuel cells.
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21.1 Section Quiz.
4. In an automobile storage battery, sulfuric acid (H2SO4) is used as the
a. cathode.
b. electrolyte.
c. anode.
d. oxidizing agent.
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21.1 Section Quiz.
5. In the hydrogen-oxygen fuel cell, the product(s) of the overall reaction is/are
a. water and hydroxide ions.
b. hydrogen and oxygen.
c. water.
d. hydroxide ions.
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