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ElectrochemWkbk - CHEM 125 Electrochem Workbook Chpt. 21...

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CHEM 125 Dr. Pizzini Electrochem Workbook Chpt. 21 C HEM 125 S PRING 2009 Electrochemistry Workbook Read Chapter 21 as listed on online syllabus. Useful Equations (…that you should understand and be able to use!) anode cathode cell E - E = E (I won’t give you this one) Q ln nF RT ˚ E E cell cell = K ln nF RT ˚ E cell = cell ˚ nFE ˚ G - = Δ At 25°C: Q ln n 0257 0 ˚ E E cell cell . = lnK n 0257 0 ˚ E cell . = Useful Constants 1 Volt = 1 Joule/Coulomb or 1 V = 1 J/C 1 Ampere = 1 Coulomb/sec or 1 A = 1 C/s Faraday constant F = 9.65 x 10 4 C/mol e - R = 8.314 J/mol K
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CHEM 125 Dr. Pizzini Electrochem Workbook Chpt. 21 Part I. Voltaic Cells 1. Assign oxidation numbers to each element in the following compounds: a. NO 2 b. SO 3 c. KClO 3 d. HNO 3 2. Assign oxidation numbers to each element in the following ions: a. ClO 3 1- b. SO 3 2- c. C 2 O 4 2- d. NO 2 1- e. BrO 1- f. AsO 4 3- 3. In each of the following reactions, identify the oxidizing and reducing agents. a. 2 NO 3 1- (aq) + 3 Cu (s) + 8 H + (aq) 2 NO (g) + 3 Cu 2+ (aq) + 4 H 2 O (l) b. 4 Fe(OH) 2 (s) + O 2 (g) + 2 H 2 O (l) Fe(OH) 3 (s) 4. Describe voltaic cells that use the following reactions. In each case, write the anode and cathode half-reactions and sketch the experimental set-up. Label the anode and cathode, identify the sign of each electrode, and indicate the direction of electron and ion flow. a. Cd (s) + Sn 2+ (aq) Cd 2+ (aq) + Sn (s) b. 2 Al (s) + 3 Cd 2+ (aq) 2 Al 3+ (aq) + 3 Cd (s) c. Cr 2 O 7 2- (aq) + 6 Fe 2+ (aq) + 14 H + (aq) 2 Cr 3+ (aq) + 6 Fe 3+ (aq) + 7 H 2 O (l) 5. Write the standard shorthand notation for each cell in #4 6. The standard potential for the following voltaic cell is 0.40 V: Zn (s) | Zn 2+ (aq) || Eu 3+ (aq), Eu 2+ (aq) | Pt (s) Using standard reduction potentials, calculate the standard reduction potential for the Eu 3+ /Eu 2+ half-cell. 7. Arrange the following oxidizing agents in order of increasing strength under standard- state conditions: Br 2 (l), MnO 4 1- (aq), Sn 4+ (aq). 8. Arrange the following reducing agents in order of increasing strength: Al(s), Na (s), and Zn (s). 9. Can Pb 2+ (aq) oxidize Al (s) or Cu (s) under standard state conditions? Calculate the standard cell potential for each reaction at 25°C.
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CHEM 125 Dr. Pizzini Electrochem Workbook Chpt. 21 10. A voltaic cell is to be constructed using the Ag/Ag + half cell and the Pb/Pb +2 half-cell. Measurement shows that the silver electrode is positive. a. Write balanced half-reactions and the overall spontaneous reaction, without using a table of half-cell potentials . b.
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This note was uploaded on 12/10/2009 for the course CHEM 125 taught by Professor Retsek during the Spring '08 term at Cal Poly.

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ElectrochemWkbk - CHEM 125 Electrochem Workbook Chpt. 21...

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