CHAPTER 17 ELECTROCHEMISTRY

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1 Advanced Chemistry Approximate Timeline Students are expected to keep up with class work when absent. CHAPTER 17 ELECTROCHEMISTRY Day Plans for the day Assignment(s) for the day 17.1 Galvanic Cells Assignment o Cell Potential 17.2 Standard Reduction Potentials Standard Reduction Potentials o Calculating Voltage o Line Notation Assignment 17.1a Read section(s) Cell Potential, Electrical Work, & Assignment 17.1b Free Energy Read section(s) Dependence of Cell Potential on Concentration Assignment 17.2 Read section(s) o The Nernst Equation o Calculation of Equilibrium Constants For Redox Reactions Batteries Assignment Corrosion Read section(s) Electrolysis o Electrolytic Cells Commercial Electrolytic Processes o Production of Aluminum o Electro-refining of Metals o Metal Plating 7 Grade & discuss assignment Review for Chapter 17 Test 8 Chapter 17 Test Read section(s) 18.1

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3 Study Guides Chapter 17 Quizzes Quiz 17.1 Galvanic Cells 1. Define the term "electrochemistry". 2. An oxidation-reduction reaction involves a transfer of electrons from the agent to the agent. 3. Recall that involves a loss of electrons and that involves a gain of electrons. 4. Define the term "galvanic cell". 5. In a battery, oxidation occurs at the and reduction occurs at the. Quiz Standard Reduction Potentials 6. In general, as the standard reduction potential becomes increasingly more positive the tendency of a chemical to be reduced becomes. 7. When E cell is a (positive/negative) number the reaction is spontaneous Cell Potential, Electrical Work, and Free Energy 8. Calculate the cell voltage for a galvanic cell. 9. Use cell voltage to determine whether or not a reaction is spontaneous.

4 Study Guide Chapter 17 Test Advanced Chemistry At the completion of chapter 17 you should 1. Know the definitions of the following terms. a. Electrochemistry b. Oxidation c. Reduction d. Oxidizing Agent e. Reducing Agent f. Salt Bridge g. Galvanic Cell h. Anode i. Cathode j. Cell Potential k. Electrolytic Cell l. Electrolysis 2. Know the difference between a galvanic cell and an electrolytic cell. 3. Know which ½ reaction occurs at the anode and which ½ reaction occurs at the cathode. 4. Use cell notation to represent redox reactions. 5. Use reduction potentials to arrange oxidizing/reducing agents in order of strength. 6. Calculate the standard voltage for any reaction. 7. Use the standard voltage to predict reaction spontaneity. 8. Relate E o, G o, and K. 9. Use the Nernst Equation to calculate the effect of concentration on cell voltage.

5 Assignment 17.0 Vocabulary Define each of the following terms. 1. Electrochemistry 2. Oxidation 3. Reduction 4. Oxidizing Agent 5. Reducing Agent 6. Salt Bridge 7. Galvanic Cell 8. Anode 9. Cathode 10. Cell Potential

6 11. Electrolytic Cell 12. Electrolysis

7 Assignment 17.1a Galvanic Cells, Cell Potentials, Standard Reduction Potentials, and Free Energy (#1) 1) Calculate Eº values for the galvanic cells given. Assume all concentrations are 1.0 M and all pressures are 1.0 atm. A) Cr 3+ (aq) + Cl 2 (g) Cr 2 O 7 2- (aq) + Cl - (aq) B) Cu 2+ (aq) + Mg (s) Mg 2+ (aq) + Cu (s) C) IO 3 - (aq) + Fe 2+ (aq) Fe 3+ (aq) + I 2 (s) D) Zn (s) + Ag + (aq) Zn 2+ (aq) + Ag (s) 2) Give the standard line notation for each cell in problem #1. A) B) C) D)

8 3) Write the balanced cell reaction and determine Eº for the galvanic cells based on the following half-reactions. Standard reduction potentials are found in Table A) Cr 2 O 7 2- (aq) + 14 H + (aq) + 6 e - 2 Cr 3+ (aq) + 7 H 2 O (l) H 2 O 2 (aq) + 2 H + (aq) + 2 e - 2 H 2 O (l) B) 2 H + (aq) + 2 e - H 2 (g) Al e - Al (s) 4) Calculate Eº for the reaction CH 3 OH (l) + 3/2 O 2 (g) CO 2 (g) + H 2 O (l) using values of ΔG f º in Appendix 4.

9 Assignment 17.1b Galvanic Cells, Cell Potentials, Standard Reduction Potentials, and Free Energy (#2) 1) Using date from Table 17.1, place the following in order of increasing strength as reducing agents (all under standard conditions). A) Cu + B) F - C) H - D) H 2 O E) I 2 F) K 2) Consider only the species Na +, Cl -, Ag +, Ag, Zn, Pb in answering the following questions. Use data from Table 17.1 A) Which if the strongest oxidizing agent? B) Which is the strongest reducing agent? C) Which species can be oxidized by SO 4 2- (aq) in acidic solution? D) Which species can be reduced by Al (s)? 3) Hydrazine is somewhat toxic. Use the half-reactions shown below to explain why household bleach (a highly alkaline solution of sodium hypochlorite) should not be mixed with household ammonia or glass cleansers that contain ammonia. A) ClO - + H 2 O + 2 e - 2 OH - + Cl - Eº = 0.90 V B) N 2 H H 2 O + 2e - 2 NH OH - Eº = V

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11 Assignment 17.2 The Nernst Equation 1) A galvanic cell is based on the following half-reactions at 25ºC. Predict whether E cell is larger or smaller than Eº for the following cases. Ag + + e - Ag H 2 O H + 2 H 2 O A) [Ag + ] = 1.0 M, [H 2 O 2 ] = 2.0 M, [H + ] = 2.0 M B) [Ag + ] = 2.0 M, [H 2 O 2 ] = 1.0 M, [H + ] = 1.0 x 10-7 M 2) The overall reaction in the lead storage battery is: Pb (s) + PbO 2 (s) + 2 H + (aq) + 2 HSO 4 - (aq) 2 PbSO 4 (s) + 2 H 2 O (l) Calculate E cell at 25ºC for this battery when [H 2 SO 4 ] = 4.5 M, that is [H + ] = [HSO 4 - ] = 4.5 M. at 25ºC, Eº = 2.04 V for the lead storage battery. 3) Consider the cell described by: Zn Zn 2+ (1.00 M) Cu 2+ (1.00 M) Cu. Calculate the cell potential after the reaction has operated long enough for the zinc ion concentration to change by 0.20 M. Assume T = 25ºC.

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13 Assignment The Nernst Equation, Cell Potential, and the Equilibrium Constant 1) Calculate ΔGº and K at 25ºC for the reactions below. A) Cl 2 (g) + 2 Br - (aq) Br 2 (aq) + 2 Cl - (aq) Eº = 0.27 V B) H 2 O (l) + 5 IO 4 - (aq) + 2 Mn 2+ 5 IO 3 - (aq) + 2 MnO 4 - (aq) + 6 H + (aq) E = 0.09 V