# Learning Goals

Learning Goal:

You will learn how to apply concepts from Chapter 5 on oxidation-reduction reactions to some very practical applications such as the electrochemical manufacture of aluminum and chlorine. You will learn how to balance an oxidation-reduction reaction, how to use standard electrode potentials to construct useful electrochemical cells, how our knowledge can be used to slow corrosion, and how very common batteries function.

Chapter Highlights:

• Define and use the terms battery, or electrochemical cell; fuel cell; electrolysis; electrode; electrolyte; salt bridge; anode; and cathode.
• Balance equations for oxidation-reduction reactions in acidic or basic solutions using the half-reaction approach (Section 21.1).
• Explain the workings of an electrochemical cell (which half-reaction occurs at the anode, which at the cathode, the polarity of the electrodes, the direction of electron flow in the external connection, and the direction of ion flow in the salt bridge) (Section 21.2)
• Appreciate the meaning of the standard electrode potential E°, and its connection to the free energy change D G° (Section 21.3).
• Recognize that product-favored reactions have a positive E°, whereas reactant-favored reactions have negative E° (Section 21.3 and Equation 21.1).
• Know that the standard hydrogen electrode (E° = 0.00 V) is the standard against which all half-reaction potentials are measured (Section 21.3).
• Appreciate the method by which standard potentials of half-reactions can be determined (Section 21.3).
• Use Table 21.1, the table of standard reduction potentials (Section 21.4).
• Understand that when a half-reaction or net electrochemical reaction is reversed, the sign E°is reversed but its value does not change (Section 21.4).
• Recognize that, as the value of E°for a reduction half-reaction becomes less negative the ion or molecule becomes a better oxidizing agent (the substance on the left is more readily reduced) (Section 21.4).
• Apply the idea that the reaction between any substance on the left in Table 21.1 (an oxidizing agent) and any substance lower than it on the right (a reducing agent) is product-favored under standard conditions (Section 21.4).
• Recognize that electrochemical potentials depend on the nature of the reactants and products and their concentrations, not on the quantities of materials used (Sections 21.4 and 21.5).
• Predict the sign and value of E°net for a redox reaction (Section 21.4).
• Use the Nernst equation (Equation 21.2) to calculate the cell potential under nonstandard conditions (Section 21.5).
• Calculate the equilibrium constant for a reaction from the value of E° (Equation 21.3 and Section 21.5).
• Recognize the difference between primary and secondary batteries (Section 21.6).
• Appreciate the chemistry and advantages and disadvantages of dry cells, alkaline batteries, mercury batteries, lithium batteries, lead storage batteries, and ni-cad batteries (Section 21.6).
• Understand the difference between batteries and fuel cells (Section 21.6).
• Understand reactions involved in corrosion and how anodic inhibition and cathodic protection can inhibit corrosion (Section 21.7).
• Describe the difference between electrolysis of an electrolyte and the operation of a galvanic or voltaic cell. (Section 21.8)
• Identify the reactions that occur in the electrolysis of a molten salt (Section 21.8).
• Characterize the reactions occurring on electrolysis of aqueous solution of electrolyte (Section 21.8).
• Use the relationship between current (amperes, A), electric charge (coulombs, C), and time (seconds, s) (Equation 21.4) and use the Faraday constant (9.65 x 104C/mol e-) (Section 21.9).
• Describe electrochemical methods for the production of aluminum, chlorine, and sodium hydroxide (Section 21.10).
Overview Web Activity:

Here are some good sites to help you with some of the topics in this chapter:

1. This one requires the Adobe Acrobat Reader (free and available at Adobe ). When you get to the site, scroll down some to the "electrochemistry section"—about 39 pages of reviews: electrochem
2. Here is a very neat site on these topics (but some of the content is at a little higher level) higher level material
3. This is a good high school site for this material stuff

Web Author: Dr. Leon L. Combs