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| Understanding the concepts
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Check your answers |
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| 1.
| Open the Oxidation-Reduction Reactions Understanding Concepts on the CD and go through the Introduction to review information about redox reactions. In the animation, what color sphere represents tin? Zinc? What are the green spheres? Go through the Example and Exercises only if your class has discussed the activity series. If not, skip the Example and Exercises.
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| 2.a.
| The only way to determine what is oxidized and what is reduced in a redox reaction is to assign oxidation states. Review the rules for assigning oxidation states in Section 17.2 of the text. For some examples on how to apply the rules, review the Examples of Oxidation States Table on the Web site.
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| b.
| Explain how to assign oxidation states to all atoms in Na2CrO4, 6H12O6, and HCO3-. |
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| 3.a.
| Some oxidation-reduction reactions can be balanced by inspection. For example, open the Dry Ice and Magnesium Visualization on the CD and view the reaction. In the video clip, magnesium is reacted with oxygen as well as with carbon dioxide. Write balanced equations for these reactions.
Hint: As indicated in the concept, magnesium displaces oxygen in CO2 forming magnesium oxide and carbon. What is oxidized and what is reduced in each reaction?
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| b.
| Other oxidation-reduction reactions are very complicated to balance. Review Section 17.4 in the text on the half-reaction method of balancing oxidation-reduction equations. Practice using this technique by balancing the equations in Problems 17.44 and 17.46 in the text.
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| 4.a.
| Open the Electrochemistry Understanding Concepts on the CD and go through the Introduction to review redox reactions and galvanic (voltaic) cells. What is the purpose of the salt bridge? Cations in a salt bridge always flow to the cathode, whereas anions in a salt bridge always flow to the anode. In terms of the zinc-tin galvanic cell illustrated in the Understanding Concepts, explain why this is the case. Which way do electrons always flow in a galvanic cell? Go through the Exercises in the Understanding Concepts only if your class has discussed the activity series. If not, skip the Exercises. |
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| b.
| For additional review material on galvanic cells, open the Galvanic Cells and the Electrochemical Half-Reactions in a Galvanic Cell Visualizations on the CD.
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| 5.
| Explain the difference between galvanic cells and electrolytic cells. A major use of electrolytic cells is the production of metals like aluminum. Open the Price of Aluminum Table on the Web site to see the effect that producing aluminum by electrolysis had on the price of aluminum. In the electrolysis of aluminum from Al2O3, is aluminum produced at the anode or the cathode?
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| 6.
| Open Key Words on the CD and test your ability to define important terms presented in Chapter 17.
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| 7.
| Test your understanding of Chapter 17 by taking the ACE quizzes on the Website.
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