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Key Concepts PowerPoint

Chapter 18
Electrochemistry

  
18-01
Title
 Galvanic cells
Caption
 Figure 18.1 (a) A strip of zinc metal is immersed in an aqueous copper sulfate solution. The redox reaction takes place at the metal-solution interface and involves direct transfer of two electrons from Zn atoms to Cu2+ions. (b) As time passes, a dark-colored deposit of copper metal appears on the zinc, and the blue color due to Cu2+(aq) fades from the solution.
Notes
 Galvanic cell in which a spontaneous chemical reaction generates an electric current.
Keywords
 galvanic cell
18-02
Title
 Galvanic cells
Caption
 Figure 18.2 (a) A galvanic cell that uses oxidation of zinc metal to Zn2+ions and reduction of Cu2+ions to copper metal. Note that the negative particles (electrons in the wire and anions in solution) travel around the circuit in the same direction. The resulting electric current can be used to light a light bulb. (b) An operating Daniell cell. The salt bridge in part (a) is replaced by a porous glass disk that allows ion flow between the anode and cathode compartments but prevents bulk mixing, which would bring Cu2+ions into direct contact with zinc and short-circuit the cell. The light bulb in part (a) is replaced with a digital voltmeter (more about this in Section 18.3).
Notes
 A galvanic cell using copper and zinc
Keywords
 galvanic cell
18-02-01UN
Title
 Anode and cathode
Caption
 The picture illustrates the difference between the anode and cathode of a typical battery.
Notes
 Anode and cathode
Keywords
 anode, cathode
18-03
Title
 A zinc anode
Caption
 Figure 18.3 Anions move toward the anode to neutralize the positive charge of the cations produced in solution when zinc metal is oxidized.
Notes
 Movement of ions around a zinc anode
Keywords
 anode, ions
18-03-01UN
Title
 Worked Example 18.1
Caption
 A galvanic cell involving iron metal and solutions of iron in its +2 and +3 oxidation states.
Notes
 Galvanic cell of iron and iron salt solutions
Keywords
 galvanic cell
18-03-02UN
Title
 Shorthand notation for galvanic cells
Caption
 The shorthand notation shows the anode half-cell on the left of the salt bridge and the cathode half-cell on the right. A single vertical line indicates the phase boundary between the metal and the metal ion solution.
Notes
 Shorthand notation for galvanic cells
Keywords
 galvanic cells, shorthand notation
18-03-03UN
Title
 Key Concept Problem 18.4
Caption
 Consider the following galvanic cell.
Notes
 Key Concept Problem 18.4
Keywords
 anode, cathode, shorthand notation
18-04
Title
 Reduction potentials of galvanic cells
Caption
 Figure 18.4 A galvanic cell consisting of a Cu2+(1 M)/Cu half-cell and a standard hydrogen electrode (S.H.E.). The S.H.E. is a piece of platinum foil that is in contact with bubbles of H2(g) at 1 atm pressure and with H+(aq) at 1 M concentration. Electrons flow from the S.H.E. (anode) to the copper cathode. The measured standard cell potential at 25°C is 0.34 V.
Notes
 A voltmeter is used to measure the standard reduction potential for the galvanic cell.
Keywords
 standard reduction potential, galvanic cell
18-05
Title
 Reduction potentials of galvanic cells
Caption
 Figure 18.5 A galvanic cell consisting of a Zn/Zn2+(1 M) half-cell and a standard hydrogen electrode. Electrons flow from the zinc anode to the S.H.E. (cathode). The measured standard cell potential at 25°C is 0.76 V.
Notes
 A voltmeter is used to measure the standard reduction potential for the galvanic cell.
Keywords
 standard reduction potential, galvanic cell
18-05-01UN
Title
 Standard reduction potentials
Caption
 Table 18.1 Standard Reduction Potentials at 25oC.
Notes
 Standard reduction potentials for various half-reactions
Keywords
 standard reduction potential
18-05-02UN
Title
 Worked Example 18.7
Caption
 Consider the following galvanic cell.
Notes
 Using the Nernst equation to determine the effect of concentration on the cell voltage
Keywords
 galvanic cell, Nernst equation
18-05-03UN
Title
 Key Concept Problem 18.11
Caption
 Consider the following galvanic cell.
Notes
 Using the Nernst equation to determine the effect of concentration on the cell voltage
Keywords
 galvanic cell, Nernst equation
18-06
Title
 Glass electrodes
Caption
 Figure 18.6 A glass electrode consists of a silver wire coated with silver chloride that dips into a reference solution of dilute hydrochloric acid. The hydrochloric acid is separated from the test solution of unknown pH by a thin glass membrane. When a glass electrode is immersed in the test solution, its electrical potential depends linearly on the difference in the pH of the solutions on the two sides of the membrane.
Notes
 Electrochemical determination of pH of solutions using a glass electrode.
Keywords
 glass electrodes
18-07
Title
 Cell potential and equilibrium
Caption
 Figure 18.7 The relationship between the equilibrium constant K for a redox reaction with n = 2 and the standard cell potential E°. Note that K is plotted on a logarithmic scale.
Notes
 Linear relationship between standard cell potential and the redox equilibrium constant
Keywords
 standard cell potential, equilibrium constant
18-08
Title
 Lead storage battery
Caption
 Figure 18.8 A lead storage battery and a cutaway view of one cell. Each electrode consists of several grids with a large surface area so that the battery can deliver the high currents required to start an automobile engine. The electrolyte is aqueous sulfuric acid.
Notes
 Structure of a typical lead storage battery showing the composition of the electrodes
Keywords
 battery
18-09
Title
 Dry cell batteries
Caption
 Figure 18.9 LeclanchZ˙ dry cell and a cutaway view.
Notes
 Structure of the dry cell battery showing the composition of the layered electrodes
Keywords
 dry cell, battery
18-10
Title
 Mercury battery
Caption
 Figure 18.10 A small mercury battery and a cutaway view.
Notes
 Structure of small mercury battery
Keywords
 battery, mercury, zinc
18-12
Title
 Hydrogen-oxygen fuel cell
Caption
 Figure 18.12 A hydrogen-oxygen fuel cell. Gaseous H2 is oxidized to water at the anode, and gaseous O2 is reduced to hydroxide ion at the cathode. The net reaction is the conversion of H2 and O2 to water.
Notes
 Schematic diagram of a hydrogen-oxygen fuel cell
Keywords
 fuel cells
18-13
Title
 Corrosion
Caption
 Figure 18.13 An electrochemical mechanism for corrosion of iron. The metal and a surface water droplet constitute a tiny galvanic cell in which iron is oxidized to Fe2+in a region of the surface (anode region) remote from atmospheric O2, and O2 is reduced near the edge of the droplet at another region of the surface (cathode region). Electrons flow from anode to cathode through the metal, while ions flow through the water droplet. Dissolved O2 oxidizes Fe2+further to Fe3+before it is deposited as rust (Fe2O3‡H2O).
Notes
 Corrosion of iron illustrated as an electrochemical process
Keywords
 iron, corrosion
18-14
Title
 Corrosion prevention
Caption
 Figure 18.14 A layer of zinc protects iron from oxidation, even when the zinc layer becomes scratched. The zinc (anode), iron (cathode), and water droplet (electrolyte) constitute a tiny galvanic cell. Oxygen is reduced at the cathode, and zinc is oxidized at the anode, thus protecting the iron from oxidation.
Notes
 Oxide coatings (such as zinc oxide) help protect iron from corrosion
Keywords
 corrosion, oxide coatings
18-15
Title
 Electrolytic cells
Caption
 Figure 18.15 Electrolysis of molten sodium chloride. Chloride ions are oxidized to Cl2 gas at the anode, and Na+ions are reduced to sodium metal at the cathode.
Notes
 Formation of sodium metal and chlorine gas through electrolysis of molten sodium chloride
Keywords
 electrolytic cell, electrolysis
18-15-01UN
Title
 Key Concept Problem 18.17
Caption
 Metallic potassium was first prepared by Humphrey Davy in 1807 by electrolysis of molten potassium hydroxide.
Notes
 Key Concept Problem 18.17
Keywords
 electrolysis, electrolytic cell
18-16
Title
 The Downs cell for sodium production
Caption
 Figure 18.16 Cross-sectional view of a Downs cell for commercial production of sodium metal by electrolysis of molten sodium chloride. The cell design keeps the sodium and chlorine apart so that they can’t react with each other.
Notes
 Sodium metal is produced commercially by the electrolysis of a mixture of molten sodium chloride and calcium chloride in a Downs cell.
Keywords
 electrolysis, Downs cell
18-17
Title
 Membrane cell
Caption
 Figure 18.17 A membrane cell for electrolytic production of Cl2 and NaOH. Chloride ion is oxidized to Cl2 gas at the anode, and water is converted to H2 gas and OH-ions at the cathode. Sodium ions move from the anode compartment to the cathode compartment through a cation-permeable membrane. Reactants (brine and water) enter the cell, and products (Cl2 gas, H2 gas, aqueous NaOH, and depleted brine) leave through appropriately placed pipes.
Notes
 Diagram of a membrane cell for production of chlorine gas and aqueous sodium hydroxide
Keywords
 electrolysis, membrane cell
18-18
Title
 The Hall-Heroult process
Caption
 Figure 18.18 An electrolytic cell for production of aluminum by the Hall-Heroult process. Molten aluminum metal forms at the graphite cathode that lines the cell. Because molten aluminum is more dense than the Al2O3-Na3AlF6 mixture, it collects at the bottom of the cell and is drawn off periodically.
Notes
 Production of aluminum metal through electrolysis of a molten Al2O3-Na3AlF6 mixture
Keywords
 electrolysis, Hall-Heroult process
18-19
Title
 Electrorefining of copper
Caption
 Figure 18.19 Electrorefining of copper metal. (a) Alternating slabs of impure copper and pure copper serve as the electrodes in electrolytic cells for the refining of copper. (b) Copper is transferred through the CuSO4 solution from the impure Cu anode to the pure Cu cathode. More easily oxidized impurities (Zn, Fe) remain in solution as cations, but noble metal impurities (Ag, Au, Pt) are not oxidized and collect as anode mud.
Notes
 Electrorefining of copper metal
Keywords
 electrolysis, copper refining
18-20
Title
 Flowchart for electrolysis calculations
Caption
 Figure 18.20 Sequence of conversions used to calculate the amount of product produced by passing a current through an electrolytic cell for a fixed period of time.
Notes
 Flowchart of steps in calculating the amount of product produced through an electrolytic process
Keywords
 electrolysis, flowchart
18-20-020UN
Title
 Key Concept Summary
Caption
 Electrochemistry key concept summary.
Notes
 Key concept summary Chapter 18
Keywords
 key concept, summary
18-20-03UN
Title
 Key Concept Problem 18.24
Caption
 The following picture of a galvanic cell has lead and zinc electrodes.
Notes
 Key Concept Problem 18.24
Keywords
 key concept, anode, cathode, galvanic cell
18-20-04UN
Title
 Key Concept Problem 18.25
Caption
 Consider the following galvanic cell.
Notes
 Key Concept Problem 18.25
Keywords
 key concept, anode, cathode, shorthand notation
18-20-05UN
Title
 Key Concept Problem 18.28
Caption
 Consider the following electrochemical cell.
Notes
 Key Concept Problem 18.28
Keywords
 galvanic, electrolytic, anode, cathode
18-20-06UN
Title
 Key Concept Problem 18.29
Caption
 It has recently been reported that porous pellets of TiO2 can be reduced to titanium metal at the cathode of an electrochemical cell containing molten CaCl2 as the electrolyte. When the TiO2 is reduced, the O2-ions dissolve in the CaCl2 and are subsequently oxidized to O2 gas at the anode. This approach may be the basis for a less expensive process for producing titanium.
Notes
 Key Concept Problem 18.29
Keywords
 anode, cathode, electrolysis
18-20-07UN
Title
 Key Concept Problem 18.30
Caption
 Consider the Daniell cell with 1.0 M ion concentrations.
Notes
 Key Concept Problem 18.30
Keywords
 key concept, Nernst equation
18-20-08UN
Title
 Key Concept Problem 18.31
Caption
 Consider the following galvanic cell with 0.10 M concentrations.
Notes
 Key Concept Problem 18.31
Keywords
 key concept, Nernst equation
18-TB01.01UN
Title
 Reduction Half-Reaction E° (V)
Caption
 Reduction Half-Reaction E° (V)
Notes
Keywords
18-TB02
Title
 Table 18.2 Relationship Between Cell Potentials E and Free-Energy Changes
Caption
Notes
Keywords
18-TB02.01UN
Title
 Half-Reaction E° (V)
Caption
 Half-Reaction E° (V)
Notes
Keywords
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