Problem Set 10 - Chem 208, Spring 2008 Problem Set 10 Due...

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Unformatted text preview: Chem 208, Spring 2008 Problem Set 10 Due Friday, April 25, 2:00 PM Suggested Additional Problems: Ch 20: 3, 7, 11, 15, 19, 21, 23, 25, 33, 35, 45, 47', Name: 57, 59,61, 65, 67 Lab TA Name: Lab Time/Room: 1. In the space below, sketch the galvanic cells based on the following overall reactions. Show the direction of electron flow, the direction of ion migration through a KN03 (aq) salt bridge, and label the cathode and anode. Write the overall balanced reaction. Finally, show the standard line notation (cell diagram). You may assume that all concentrations are 1.0 M and all partial pressures are 1.0 atrn. You can use information from Table 20.1 from your text. a)Cu2+(aq) + Ca(s) —> Caz+(aq) + Cu(s) b) Mn04_(aq) + Cl_(aq) —> C12(g) + Mn2+(aq) (in acidic solution) Chem 208, Spring 2008 Problem Set 10 Due Friday, April 25, 2:00 PM 2. Referring to Table 20.1 or D4 in your text, answer the following. Briefly justify your answer. a) Is H+(aq) capable of oxidizing Mg(s)? b) Is Fe3+(aq) capable of oxidizing I_( aq)? c) Is H2(g) capable of reducing Sn2+(aq)? d) Is Fez+(aq) capable of reducing Cr3+(aq) to Cr2+(aq)? e) Is Fe2+(aq) capable of reducing Cr2+(aq) to Cr(s)? 3. Calculate the standard electrode potential E°ceu for the following reaction using standard Gibbs free energies of formation from your text. Note that one of the half reactions is 3 H200) + CH3CH20HU) —> 2 C02(g) + 12 H+(aq) + 12 e‘ . CH3CH20H([) + 3 02(g) —> 2 C02(g) + 3 H200) Chem 208, Spring 2008 Problem Set 10 Due Friday, April 25, 2:00 PM 4. An electrochemical cell consists of a standard hydrogen electrode and a silver metal electrode. a) What is the potential of the cell at 25°C if the silver electrode is placed in a solution in which [Ag+] : 1.2 x 10'4M ? b) If the silver electrode is placed in a solution of 0. 10 M NaBr that is saturated with AgBr, what is the cell potential at 25°C? The K51, for 5.0 x 10'‘3 for AgBr. (Hint: calculate [Ag*].) c) The silver electrode is placed in a solution of unknown [Ag+]. The measured potential at 25°C is 0.610 v. What is [Ag+] ? d) If you wished to construct a calibration curve to determine how the cell potential varies with [Ag+], what would you plot in order to yield a straight line? What would be the slope? Chem 208, Spring 2008 Problem Set 10 Due Friday, April 25, 2:00 PM 5. Consider the electrochemical cell, operating under acidic conditions, formed by counecting the following half cells: Al3+(aq) + 3e" —> Al(s) E°= -l.706V Mn04"(aq) + 8H+(aq) + Se— —> Mn2+(aq) + 4H20(l) E0= 1.491 V Note: The second cell utilizes a Pt electrode. a) At which electrode will reduction occur spontaneously? b) Which electrode is the anode? 0) Write the balanced cell reaction for the above galvanic cell. d) Assuming that the concentrations of all species in solution are 1.0 M and the temperature is 250C, what is the measured cell potential (E0 I) in volts? col 6) The above cell is operated for a period of 6.50 hours, producing an average current of 0.750 Amp i) What is the change in mass ofthe aluminum electrode in grams? A1 = 26.98 g/mol. ii) Assume that 500.0 ml of 1.00 M M34r solution was initially present and that the volume of solution remained constant. What is the final concentration of A13+ ? f) Calculate the cell potential (Emu) if the cell is operated with the following concentrations: [Al3+] = 0.05 M [Mn2+] = 1.30 M [Mn04—1 = 0.25 M pH : 0.50 ...
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This note was uploaded on 05/13/2008 for the course CHEM 342132 taught by Professor Davis during the Spring '08 term at Cornell University (Engineering School).

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Problem Set 10 - Chem 208, Spring 2008 Problem Set 10 Due...

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