INTRODUCTION: One general category of chemical reactions is the oxidation-reduction reaction (called “redox” for short). These reactions are characterized by an exchange of electrons. In these reactions electrons move from one substance to another. This process occurs because of the difference in the activity or reactivity of the different materials, which exchange electrons. This transfer of electrons occurs in all reactions where elements combine and become compounds. It is most obvious in the formation of ionic compounds. However, this process can also occur between metals and metal ions. Indeed, redox reactions are what give batteries their power and energy. Batteries are simply specially designed redox reactions in which the two components of the reaction are separated. When connected by a conducting material, the transferred electrons can be made to do work like start a car or run a radio. In this unit we will learn about redox reactions in general and then discuss their application in voltaic and electrochemical cells.
OBJECTIVES: As you study this unit, you should be able to do the following:
Define oxidation and reduction. (20-1)
Identify the oxidizing and reducing agent in a redox reaction and give the characteristics of a redox reaction. (20-1)
Assign oxidation numbers to atoms in compounds. (20-1)
Utilize the activity series of metals to predict redox reactions. (20-2).
Apply the oxidation-number change method to balance redox equations. (20-4)
Describe electrochemical cells. (21-1)
Explain the operation of a voltaic cell using a sketch, labeling the cathode, the anode, and the direction of electron flow. (21-2)
Relate standard electrode potentials to standard cell potentials. (21-2)
Calculate cell potentials for voltaic and electrolytic cells. (21-2 and 21-4)
Give some examples of common commercial cells and batteries. (21-3)
Distinguish between electrolytic and voltaic cells and
list some applications of each. (21-2
and 21-4)
LEARNING ACTIVITIES:
To learn about objectives 1-5:
READ Chapter 20, pp. 656-678.
WRITE answers to questions: 1-8, 14, 15, 20, 24, 26-28 found on pp. 680-681.
WRITE answers to questions 1, 4, 5, 16, 19, 20 found on pp. 715-716.
WRITE worksheet "GIA8-1: Oxidation Numbers and Redox Agents"
WRITE worksheet "GIA8-2: Balancing Redox Reactions"
WRITE worksheet "GIA8-3: Balancing Redox Reactions Using Half - Reactions"
READ and PERFORM Lab: “Permanganate Reaction with Oxalic Acid.”
TAKE computer based Post-Test on “Visualizing Reactions Types: Redox Reactions, Post-Test”
To learn about objectives 6-11:
READ Chapter 21, pp. 682-709.
WRITE answers to end of the chapter question #s 1-9, 18, 19, 22, 26, 27 found on pp. 712-713 and Unit Review Questions 10, 22, 23 on pp 716-717.
READ and PERFORM Lab: “Making the Blob?”
TAKE computer based tutorial, “Electrochemistry: Standard Potential” tutorial from MCWeb.
To make sure you understand the objectives for this unit:
ASK me, the teacher, any lingering QUESTIONS
TAKE the Unit’s Self-Test
Due Dates:
Computer-based “Visualizing Reactions Types: Redox Reactions, Post-Test” due .
Quiz on Chapter 20: [Objectives 1-5]
Ch. 20 questions: Same day as quiz.
Lab Write-up for “Permanganate Reaction with Oxalic Acid” due one week after the lab is completed.
Lab Write-up for “Making the Blob?” due one week after the lab is completed.
Computer-based tutorial “Electrochemistry: Standard Potential” due .
TEST on Unit 8: Monday, April 29th (April 30th for G-block).
Ch. 21 questions: on day of test, see above.
