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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.
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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 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 Electrochemical Processes • For any two metals in an activity series, the more active metal is the more readily oxidized.
21.1 Electrochemical Processes • A Spontaneous Redox Reaction
21.1 Electrochemical Processes
21.1 Electrochemical Processes
21.1 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 Voltaic Cells • Voltaic Cells • How does a voltaic cell produce electrical energy?
21.1 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 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 saltbridge—a tube containing a strong electrolyte, often potassium sulfate (K2SO4).
21.1 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 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 Voltaic Cells • How a Voltaic Cell Works
21.1 Electrochemical Cells > Voltaic Cells
21.1 Electrochemical Cells > Voltaic Cells
21.1 Electrochemical Cells > Voltaic Cells
21.1 Electrochemical Cells > Voltaic Cells
21.1 Electrochemical Cells > Voltaic Cells
21.1 Voltaic Cells • Representing Electrochemical Cells • You can represent the zinc-copper voltaic cell using the following shorthand.
21.1 Using Voltaic Cells as Energy Sources • Using Voltaic Cells as Energy Sources • What current technologies use electrochemical processes to produce electrical energy?
21.1 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 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 Using Voltaic Cells as Energy Sources • Both dry cells and alkaline batteries are single electrochemical cells that produce about 1.5 V.
21.1 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 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 Using Voltaic Cells as Energy Sources
21.1 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 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 Section Quiz. • 21.1.
21.1 Section Quiz. • 1. Zn is above Pb in the activity series of metals. Which of the following statements is correct? • Zn will react with Pb2+. • Pb2+ will react with Zn2+. • Zn2+ will react with Pb. • Pb will react with Zn2+.
21.1 Section Quiz. • 2. The reactions that take place in electrochemical cells involve electron transfers. What name is given to such reactions? • oxidation reactions • reduction reactions • spontaneous redox reactions • double replacement reactions
21.1 Section Quiz. • 3. Portable sources of electrical energy consisting of groups of voltaic cells connected together are called • batteries • alkaline cells. • dry cells. • fuel cells.
21.1 Section Quiz. • 4. In an automobile storage battery, sulfuric acid (H2SO4) is used as the • cathode. • electrolyte. • anode. • oxidizing agent.
21.1 Section Quiz. • 5. In the hydrogen-oxygen fuel cell, the product(s) of the overall reaction is/are • water and hydroxide ions. • hydrogen and oxygen. • water. • hydroxide ions.
