Lesson Plans

Chemistry: The Central Science 9th Edition ©2003

by Brown, LeMay, and Bursten

Weeks 25–26: Redox Reactions and Electrochemistry

Chapter 20: Electrochemistry

College Board Performance Objectives:

• Identify redox reactions, the species oxidized, reduced, the oxidizing agent, and the reducing agent.
• Balance redox reactions by using oxidation number method and half-reactions method.
• Diagram and label electrochemical cells, both voltaic and electrolytic.
• Calculate emf of voltaic cell given electrode potentials.
• Given electrode potentials predict if a reaction is spontaneous.
• Interconvert E°, G°, and K for a redox reaction.
• Be able to calculate any variable in the Nernst equation given the others.
• Calculate time, current, or amount of a substance produced by electrolysis given the other two.
• Calculate the maximum electrical work performed by a voltaic cell.

College Board Lab Objectives:

• Use electrolysis to determine the value of the faraday and Avogadro's number.
• Learn to construct electrolytic and voltaic cells.
• Measure the potential of a voltaic cell at various temperatures.
• Calculate G, H, and S.

Suggested Labs:

• Experiment 16, Electrolysis, the Faraday, and Avogadro's Number, p. 169
• Experiment 17, Electrochemical Cells and Thermodynamics, p. 175

Resources:

• Instructor's Resource Manual, pp. 253–266
• Student's Guide, pp. 424–448
• Test Bank, pp. 675–697
• Instructor's Resource CD, Chapter 20

Pacing Guide:

• Identifying and Balancing Redox Reactions—2 days
• Voltaic Cells—1 day
• E°, Standard Reduction Potential—1 day
• Spontaneity of Redox Reactions, G° = –nFE°—1 day
• Nernst equation: E = E° – log Q—2 days
• The Faraday; Faraday's Laws and Stoichiometry - 2 days
• Block Scheduling
  Recognizing redox reactions, which substance is oxidized, which is reduced, and balancing redox reactions will take about one and one-half blocks. The voltaic cell and its anatomy could fill the rest of the second block. After understanding and working with standard reduction potentials, show how they are related to spontaneity and Q. This should require one whole block of time. Next, spend a block on Faraday's laws and stoichiometry. Batteries and corrosion are interesting topics, but they are not necessary for the exam.

Key Words:

Suggested Exercises:
Critical thinking questions and end-of-chapter activities are included in these exercises.

• pp. 821–829, # 1, 3, 5, 7, 9, 11, 13, 15, 17, 19, 21, 23, 25, 27, 29, 31, 33, 35, 37, 39, 41, 43, 45, 47, 49, 51, 53, 55, 57, 59, 71, 73, 79, 81, 90, 93, 103. 110;
• eMedia Exercise: # 118, 120, 121, 122.

Troubleshooting Tips/Error Traps:

• In all electrochemical cells (voltaic and electrolytic) oxidation takes place at the anode and reduction at the anode. In determining E° for a cell, or a reaction, do not multiply the E°_sp of either reactant by the stoichiometric coefficient.